Re: [Xen-devel] [PATCH 4/7] arm: smccc: handle SMCs according to SMCCC

[Jan Beulich]

>>> On 17.08.17 at 14:35,  wrote:
> On Thu, Aug 17, 2017 at 01:45:54AM -0600, Jan Beulich wrote:
>> >>> On 16.08.17 at 23:41,  wrote:
>> > On Wed, Aug 09, 2017 at 05:58:19AM -0600, Jan Beulich wrote:
>> >> > On 08/08/17 21:08, Volodymyr Babchuk wrote:
>> >> >> +#ifndef __XEN_PUBLIC_ARCH_ARM_SMC_H__
>> >> >> +#define __XEN_PUBLIC_ARCH_ARM_SMC_H__
>> >> >> +
>> >> >> +typedef struct {
>> >> >> +uint32_t a[4];
>> >> >> +} xen_arm_smccc_uid;
>> >> 
>> >> This is not the normal way of encoding a UID type.
>> > I thought about this. According to RFC 4122, UUID should be defined like 
>> > this:
>> > struct xen_uuid_rfc_4122 {
>> > u32 time_low;  /* low part of timestamp */
>> > u16 time_mid;  /* mid part of timestamp */
>> > u16 time_hi_and_version;   /* high part of timestamp and 
>> > version */
>> > u8  clock_seq_hi_and_reserved; /* clock seq hi and variant */
>> > u8  clock_seq_low; /* clock seq low */
>> > u8  node[6];   /* nodes */
>> > };
>> > 
>> > This resembles structure of RFC, but it is highly inconvenient to use. The 
>> > most
>> > used operation for UUIDs is comparison, I think. Next popular operations 
>> > are
>> > serialization and deserialization. All those are very trivial, if you are 
>> > using
>> > array instead of separate fields. I just checked Linux kernel, it uses 
>> > array
>> > of 16 u8s. I used array of four u32s because this is how it is represented 
>> > in
>> > SMC convention.
>> 
>> In our tree, see e.g. struct xenpf_efi_guid and EFI_GUID plus the
>> "conversion" function between them (cast_guid()).
> There are two EFI_GUID definitions in xen tree. One is in 
> tools/libxc/xc_efi.h,

When I talk about the Xen tree, I normally mean the xen/ sub-tree
of xen.git.

> where guid defined in linux style:
> typedef struct {
> uint8_t b[16];
> } efi_guid_t;
> 
> Another is in xen/include/efi/efidef.h, and it is defined in Microsoft 
> style:
> typedef struct {  
> UINT32  Data1;
> UINT16  Data2;
> UINT16  Data3;
> UINT8   Data4[8]; 
> } EFI_GUID;  
> 
> I assume, that you meant second one.
> Anyways, both of them are for EFI code and are not publicly exported.

But struct xenpf_efi_guid is.

>> > Now I'm going to create separate public header for UUIDs.
>> 
>> I don't see the need for a separate header.
> Look, I was asked to provide XEN SMCCC UUID in public headers. To do that,
> I need some structure to hold UUID. There are two ways: I can either
> introduce public struct xen_uuid, which later can be used by anyone.
> In this case it should have some generic structure (RFC4122 compatible,
> Linux compatible, Microsoft compatible, or some XEN way). In another words,
> everyone should be happy with it.

Right, but that _still_ does not require you to add a new header. I'd
see such a relatively generic type go into xen.h.

> Either it can be SMCCC-only structure. Then it can live in public SMCCC 
> header,
> it can have definition that is suitable for SMCCC use, and I'm not obligued
> to make it compatible with any other UUID definition standard. According to
> SMCCC, UUID is presented as four 32-bit fields. This is exactly what I did
> there.
> 
> So, if you are saying, that there are no need for a separate header, then I
> can use the second approach, right?

As per above - no, not really.

>> >And I'm not sure
>> > that RFC 4122 approach is the best. Serialization code for that structure
>> > will require some fiddling with binary shifts. Personally I stick to the
>> > Linux way (uint8_t data[16]).
>> > So, I'm interested in maintainers opinion.
>> > 
>> >> >> +#define XEN_ARM_SMCCC_UID(a, b, c, d0, d1, d2, d3, d4, d5, d6, d7)
>> >> >>   \
>> >> >> +((xen_arm_smccc_uid) {{(a), ((b) << 16 | (c) ),   
>> >> >>   \
>> >> 
>> >> This is not C89 compatible.
>> > 
>> > I'm sorry, but I not quite sure why this is not C89 compatible. According 
>> > to [1]
>> > C89 supports initializer lists.
>> 
>> It's the (){} style which C89 doesn't support
>> afaik, and ...
> I wrote this small test program:
> 
> #include 
> 
> struct test
> {
>   int a[2];
> };
> 
> int main (int argc, char* argv[])
> {
>   printf("%d\n", ((struct test){{1,2}}).a[0]);
>   return 0;
> }
> 
> It is compiles with gcc --std=c89 without warnings.

Sure, because afaik gcc keeps its extensions enabled in that mode.
Try a compiler that is _not_ gcc or C99 compatible.

>> >> >> +((d0) << 24 | (d1) << 16 | (d2) << 8 | (d3) << 0),
>> >> >>   \
>> >> >> +((d4) << 24 | (d5) << 16 | (d6) << 8 | (d7) << 0)}})
>> >> >> +
>> > 
>> > [1] http://port70.net/~nsz/c/c89/c89-draft.html#3.5.7 
>> 
>> ... this also doesn't have anything like that.
> I'm sorry, I don't get what do you mean under "this".

It means the document you referred to.

Jan

Re: [Xen-devel] [PATCH 4/7] arm: smccc: handle SMCs according to SMCCC

[Julien Grall]

Hi,

On 17/08/17 13:35, Volodymyr Babchuk wrote:

I wrote this small test program:

#include 

struct test
{
int a[2];
};

int main (int argc, char* argv[])
{
printf("%d\n", ((struct test){{1,2}}).a[0]);
return 0;
}

It is compiles with gcc --std=c89 without warnings.


This is because GCC supports compounds literals in C89 as an extension 
(see [1]).





+((d0) << 24 | (d1) << 16 | (d2) << 8 | (d3) << 0),  \
+((d4) << 24 | (d5) << 16 | (d6) << 8 | (d7) << 0)}})
+


[1] http://port70.net/~nsz/c/c89/c89-draft.html#3.5.7


... this also doesn't have anything like that.

I'm sorry, I don't get what do you mean under "this".


The web page does not mention (){}. Which is normal 
because this also appears in c99 (see [2]).





Jan



Cheers,

[1] https://gcc.gnu.org/onlinedocs/gcc-4.3.1/gcc/Compound-Literals.html
[2]  http://en.cppreference.com/w/c/language/compound_literal

--
Julien Grall

___
Xen-devel mailing list
Xen-devel@lists.xen.org
https://lists.xen.org/xen-devel

Re: [Xen-devel] [PATCH 4/7] arm: smccc: handle SMCs according to SMCCC

[Volodymyr Babchuk]

Hi Jan,

On Thu, Aug 17, 2017 at 01:45:54AM -0600, Jan Beulich wrote:
> >>> On 16.08.17 at 23:41,  wrote:
> > Hello Jan,
> > 
> > On Wed, Aug 09, 2017 at 05:58:19AM -0600, Jan Beulich wrote:
> > 
> >> 
> >> > On 08/08/17 21:08, Volodymyr Babchuk wrote:
> >> >> +#ifndef __XEN_PUBLIC_ARCH_ARM_SMC_H__
> >> >> +#define __XEN_PUBLIC_ARCH_ARM_SMC_H__
> >> >> +
> >> >> +typedef struct {
> >> >> +uint32_t a[4];
> >> >> +} xen_arm_smccc_uid;
> >> 
> >> This is not the normal way of encoding a UID type.
> > I thought about this. According to RFC 4122, UUID should be defined like 
> > this:
> > struct xen_uuid_rfc_4122 {
> > u32 time_low;  /* low part of timestamp */
> > u16 time_mid;  /* mid part of timestamp */
> > u16 time_hi_and_version;   /* high part of timestamp and 
> > version */
> > u8  clock_seq_hi_and_reserved; /* clock seq hi and variant */
> > u8  clock_seq_low; /* clock seq low */
> > u8  node[6];   /* nodes */
> > };
> > 
> > This resembles structure of RFC, but it is highly inconvenient to use. The 
> > most
> > used operation for UUIDs is comparison, I think. Next popular operations are
> > serialization and deserialization. All those are very trivial, if you are 
> > using
> > array instead of separate fields. I just checked Linux kernel, it uses array
> > of 16 u8s. I used array of four u32s because this is how it is represented 
> > in
> > SMC convention.
> 
> In our tree, see e.g. struct xenpf_efi_guid and EFI_GUID plus the
> "conversion" function between them (cast_guid()).
There are two EFI_GUID definitions in xen tree. One is in tools/libxc/xc_efi.h,
where guid defined in linux style:
typedef struct {
uint8_t b[16];
} efi_guid_t;

Another is in xen/include/efi/efidef.h, and it is defined in Microsoft style:
typedef struct {  
UINT32  Data1;
UINT16  Data2;
UINT16  Data3;
UINT8   Data4[8]; 
} EFI_GUID;  

I assume, that you meant second one.
Anyways, both of them are for EFI code and are not publicly exported.

> > Now I'm going to create separate public header for UUIDs.
> 
> I don't see the need for a separate header.
Look, I was asked to provide XEN SMCCC UUID in public headers. To do that,
I need some structure to hold UUID. There are two ways: I can either
introduce public struct xen_uuid, which later can be used by anyone.
In this case it should have some generic structure (RFC4122 compatible,
Linux compatible, Microsoft compatible, or some XEN way). In another words,
everyone should be happy with it.

Either it can be SMCCC-only structure. Then it can live in public SMCCC header,
it can have definition that is suitable for SMCCC use, and I'm not obligued
to make it compatible with any other UUID definition standard. According to
SMCCC, UUID is presented as four 32-bit fields. This is exactly what I did
there.

So, if you are saying, that there are no need for a separate header, then I
can use the second approach, right?

> >And I'm not sure
> > that RFC 4122 approach is the best. Serialization code for that structure
> > will require some fiddling with binary shifts. Personally I stick to the
> > Linux way (uint8_t data[16]).
> > So, I'm interested in maintainers opinion.
> > 
> >> >> +#define XEN_ARM_SMCCC_UID(a, b, c, d0, d1, d2, d3, d4, d5, d6, d7) 
> >> >>  \
> >> >> +((xen_arm_smccc_uid) {{(a), ((b) << 16 | (c) ),
> >> >>  \
> >> 
> >> This is not C89 compatible.
> > 
> > I'm sorry, but I not quite sure why this is not C89 compatible. According 
> > to [1]
> > C89 supports initializer lists.
> 
> It's the (){} style which C89 doesn't support
> afaik, and ...
I wrote this small test program:

#include 

struct test
{
int a[2];
};

int main (int argc, char* argv[])
{
printf("%d\n", ((struct test){{1,2}}).a[0]);
return 0;
}

It is compiles with gcc --std=c89 without warnings.

> >> >> +((d0) << 24 | (d1) << 16 | (d2) << 8 | (d3) << 0), 
> >> >>  \
> >> >> +((d4) << 24 | (d5) << 16 | (d6) << 8 | (d7) << 0)}})
> >> >> +
> > 
> > [1] http://port70.net/~nsz/c/c89/c89-draft.html#3.5.7 
> 
> ... this also doesn't have anything like that.
I'm sorry, I don't get what do you mean under "this".

> Jan
> 

___
Xen-devel mailing list
Xen-devel@lists.xen.org
https://lists.xen.org/xen-devel

Re: [Xen-devel] [PATCH 4/7] arm: smccc: handle SMCs according to SMCCC

[Jan Beulich]

>>> On 16.08.17 at 23:41,  wrote:
> Hello Jan,
> 
> On Wed, Aug 09, 2017 at 05:58:19AM -0600, Jan Beulich wrote:
> 
>> 
>> > On 08/08/17 21:08, Volodymyr Babchuk wrote:
>> >> +#ifndef __XEN_PUBLIC_ARCH_ARM_SMC_H__
>> >> +#define __XEN_PUBLIC_ARCH_ARM_SMC_H__
>> >> +
>> >> +typedef struct {
>> >> +uint32_t a[4];
>> >> +} xen_arm_smccc_uid;
>> 
>> This is not the normal way of encoding a UID type.
> I thought about this. According to RFC 4122, UUID should be defined like 
> this:
> struct xen_uuid_rfc_4122 {
> u32 time_low;  /* low part of timestamp */
> u16 time_mid;  /* mid part of timestamp */
> u16 time_hi_and_version;   /* high part of timestamp and version 
> */
> u8  clock_seq_hi_and_reserved; /* clock seq hi and variant */
> u8  clock_seq_low; /* clock seq low */
> u8  node[6];   /* nodes */
> };
> 
> This resembles structure of RFC, but it is highly inconvenient to use. The 
> most
> used operation for UUIDs is comparison, I think. Next popular operations are
> serialization and deserialization. All those are very trivial, if you are 
> using
> array instead of separate fields. I just checked Linux kernel, it uses array
> of 16 u8s. I used array of four u32s because this is how it is represented in
> SMC convention.

In our tree, see e.g. struct xenpf_efi_guid and EFI_GUID plus the
"conversion" function between them (cast_guid()).

> Now I'm going to create separate public header for UUIDs.

I don't see the need for a separate header.

>And I'm not sure
> that RFC 4122 approach is the best. Serialization code for that structure
> will require some fiddling with binary shifts. Personally I stick to the
> Linux way (uint8_t data[16]).
> So, I'm interested in maintainers opinion.
> 
>> >> +#define XEN_ARM_SMCCC_UID(a, b, c, d0, d1, d2, d3, d4, d5, d6, d7)  \
>> >> +((xen_arm_smccc_uid) {{(a), ((b) << 16 | (c) ), \
>> 
>> This is not C89 compatible.
> 
> I'm sorry, but I not quite sure why this is not C89 compatible. According to 
> [1]
> C89 supports initializer lists.

It's the (){} style which C89 doesn't support
afaik, and ...

>> >> +((d0) << 24 | (d1) << 16 | (d2) << 8 | (d3) << 0),  \
>> >> +((d4) << 24 | (d5) << 16 | (d6) << 8 | (d7) << 0)}})
>> >> +
> 
> [1] http://port70.net/~nsz/c/c89/c89-draft.html#3.5.7 

... this also doesn't have anything like that.

Jan


___
Xen-devel mailing list
Xen-devel@lists.xen.org
https://lists.xen.org/xen-devel

Re: [Xen-devel] [PATCH 4/7] arm: smccc: handle SMCs according to SMCCC

[Volodymyr Babchuk]

Hello Jan,

On Wed, Aug 09, 2017 at 05:58:19AM -0600, Jan Beulich wrote:

> 
> > On 08/08/17 21:08, Volodymyr Babchuk wrote:
> >> +#ifndef __XEN_PUBLIC_ARCH_ARM_SMC_H__
> >> +#define __XEN_PUBLIC_ARCH_ARM_SMC_H__
> >> +
> >> +typedef struct {
> >> +uint32_t a[4];
> >> +} xen_arm_smccc_uid;
> 
> This is not the normal way of encoding a UID type.
I thought about this. According to RFC 4122, UUID should be defined like this:
struct xen_uuid_rfc_4122 {
u32 time_low;  /* low part of timestamp */
u16 time_mid;  /* mid part of timestamp */
u16 time_hi_and_version;   /* high part of timestamp and version */
u8  clock_seq_hi_and_reserved; /* clock seq hi and variant */
u8  clock_seq_low; /* clock seq low */
u8  node[6];   /* nodes */
};

This resembles structure of RFC, but it is highly inconvenient to use. The most
used operation for UUIDs is comparison, I think. Next popular operations are
serialization and deserialization. All those are very trivial, if you are using
array instead of separate fields. I just checked Linux kernel, it uses array
of 16 u8s. I used array of four u32s because this is how it is represented in
SMC convention.
Now I'm going to create separate public header for UUIDs. And I'm not sure
that RFC 4122 approach is the best. Serialization code for that structure
will require some fiddling with binary shifts. Personally I stick to the
Linux way (uint8_t data[16]).
So, I'm interested in maintainers opinion.

> >> +#define XEN_ARM_SMCCC_UID(a, b, c, d0, d1, d2, d3, d4, d5, d6, d7)  \
> >> +((xen_arm_smccc_uid) {{(a), ((b) << 16 | (c) ), \
> 
> This is not C89 compatible.

I'm sorry, but I not quite sure why this is not C89 compatible. According to [1]
C89 supports initializer lists.

> 
> >> +((d0) << 24 | (d1) << 16 | (d2) << 8 | (d3) << 0),  \
> >> +((d4) << 24 | (d5) << 16 | (d6) << 8 | (d7) << 0)}})
> >> +

[1] http://port70.net/~nsz/c/c89/c89-draft.html#3.5.7

___
Xen-devel mailing list
Xen-devel@lists.xen.org
https://lists.xen.org/xen-devel

Re: [Xen-devel] [PATCH 4/7] arm: smccc: handle SMCs according to SMCCC

[Volodymyr Babchuk]

Hi Julien,

On 11.08.17 00:09, Julien Grall wrote:



On 10/08/2017 21:09, Volodymyr Babchuk wrote:

Hi,

On 10.08.17 21:18, Julien Grall wrote:

Hi,

On 10/08/17 18:40, Volodymyr Babchuk wrote:



On 10.08.17 19:11, Julien Grall wrote:



On 10/08/17 16:33, Volodymyr Babchuk wrote:

Hi Julien,

On 09.08.17 13:10, Julien Grall wrote:

Hi Volodymyr,

CC "THE REST" maintainers to get an opinion on the public headers.

On 08/08/17 21:08, Volodymyr Babchuk wrote:

SMCCC (SMC Call Convention) describes how to handle both HVCs and
SMCs.
SMCCC states that both HVC and SMC are valid conduits to call to a
different
firmware functions. Thus, for example PSCI calls can be made 
both by

SMC or HVC. Also SMCCC defines function number coding for such
calls.
Besides functional calls there are query calls, which allows
underling
OS determine version, UID and number of functions provided by
service
provider.

This patch adds new file `vsmc.c`, which handles both generic SMCs
and HVC according to SMC. At this moment it implements only one
service: Standard Hypervisor Service.

Standard Hypervisor Service only supports query calls, so caller 
can

ask about hypervisor UID and determine that it is XEN running.

This change allows more generic handling for SMCs and HVCs and it
can
be easily extended to support new services and functions.

But, before SMC is forwarded to standard SMCCC handler, it can be
routed
to a domain monitor, if one is installed.

Signed-off-by: Volodymyr Babchuk 
Reviewed-by: Oleksandr Andrushchenko

Reviewed-by: Oleksandr Tyshchenko 
---
 - Updated description to indicate that this patch affects only SMC
call path.
 - added "xen_" prefix to definitions in
include/public/arch-arm/smc.h
 - moved do_trap_smc() into vsmc.c from traps.c
 - replaced all tabs with spaces


I would have really appreciated a summary of the discussion we 
had on

the previous version regarding the bindings. This is a real blocker
for this series and should not be ignored.



While I agree that question about bindings is important, I can't
see how
it affects this patch series. This patch series does not break
anything.
Because

1. This series add only new feature: generic hypervisor service
with no
immediate use. All ARM guests are already aware that they are
running on
XEN. All ARM guests know that they call *only* PSCI.

2. I see importance of this patch series for embedded platforms, 
where

developer exactly knows what software of which version he/she will
run.
I doubt that server platforms will need something beyond PSCI, 
which I

preserved as is.


I disagree here. SMCCC could be used to provide Dom0 a way to interact
with the firmware if necessary.

AFAIK, Dom0 usually is built with particular version of XEN in mind (or
at least minimal XEN version).


That's not true. Dom0 is a generic kernel able to probe everything
from the firmware tables and Xen interface. I use the exact Linux
kernel on multiple platforms with no issue.

Okay, I was speaking about embedded use case.


Bear in mind that Xen is not only embedded. When you upstream a new 
feature you have to think about how this could be used by anyone.



The Hypervisor and Dom0 (Linux, FreeBSD) are different projects with
different release cadence. We provide a stable interface that is
backward compatible (returning error code for non-existent
hypercalls). So a Linux released in 10 years should still work on Xen
4.10 and adapt to the features available.

I just want to clarify this. At least four hypercalls are not backward
compatible: platform_op, sysctl, domctl and flask_op. I had a problem
with this, when played with MiniOS-based monitor. Sure, your kernel will
boot up, but some well known XEN services will be absent.
This have nothing with SMC bindings problem, though.


I am not sure to follow here... Were they ever be supported on ARM? If 
not, then it is no a backward compatibility issue. You cannot assume 
that all the hypercalls existing on x86 will be available on ARM.


For a list of known available/supported hypercalls for ARM see:
public/include/arch-arm.h.

Also bear in mind that some hypercalls are not part of the stable ABI. 
For instance domctls are not stable and it is well-known that you have 
to rebuild your app for every new Xen versions...


But domctls will never be used in Linux Kernel as they only meant to be 
used to control a domain.








A I'm not denying importance of SMC bindings, but I think it is not
blocker for my patches. We can add bindings later, when there will be
consensus on how they should look. In meantime SMC handler can be 
used

by anyone who knows that is available.


I am not in favor on getting something merged in Xen until we agree on
the way for the guest to know it is there.

I think that SMC implementation will be the same, regardless the way we
can tell guest that it is available. At this time guests can safely
assume 

Re: [Xen-devel] [PATCH 4/7] arm: smccc: handle SMCs according to SMCCC

[Julien Grall]

Hi Volodymyr,

On 10/08/17 22:09, Julien Grall wrote:


We can stick to XEN-only approach, like XENFEAT_* or "xen,smccc" in DT.
But is this right?


Answering to this question after some thoughts and discussion around.

The generic approach is indeed the best solution, however I am afraid it 
will take some times to get ready and might not be ready for Xen 4.10.


As I mentioned earlier, I don't want to merge this without any way to 
discover the existence of SMCCC in the hypervisor. I also understand 
that you would like to get this merged in Xen 4.10.


So the alternative we have is to provide a XEN-only approach for the 
time being. It has to work for both ACPI and DT, this likely means we 
want a XENFEAT_* flag.


That alternative would be supersede when the generic approach will be 
available. Though we would have to keep both around, but it is it not a 
big deal.


Does it make sense?

Cheers,

--
Julien Grall

___
Xen-devel mailing list
Xen-devel@lists.xen.org
https://lists.xen.org/xen-devel

Re: [Xen-devel] [PATCH 4/7] arm: smccc: handle SMCs according to SMCCC

[Julien Grall]

On 10/08/2017 21:09, Volodymyr Babchuk wrote:

Hi,

On 10.08.17 21:18, Julien Grall wrote:

Hi,

On 10/08/17 18:40, Volodymyr Babchuk wrote:



On 10.08.17 19:11, Julien Grall wrote:



On 10/08/17 16:33, Volodymyr Babchuk wrote:

Hi Julien,

On 09.08.17 13:10, Julien Grall wrote:

Hi Volodymyr,

CC "THE REST" maintainers to get an opinion on the public headers.

On 08/08/17 21:08, Volodymyr Babchuk wrote:

SMCCC (SMC Call Convention) describes how to handle both HVCs and
SMCs.
SMCCC states that both HVC and SMC are valid conduits to call to a
different
firmware functions. Thus, for example PSCI calls can be made both by
SMC or HVC. Also SMCCC defines function number coding for such
calls.
Besides functional calls there are query calls, which allows
underling
OS determine version, UID and number of functions provided by
service
provider.

This patch adds new file `vsmc.c`, which handles both generic SMCs
and HVC according to SMC. At this moment it implements only one
service: Standard Hypervisor Service.

Standard Hypervisor Service only supports query calls, so caller can
ask about hypervisor UID and determine that it is XEN running.

This change allows more generic handling for SMCs and HVCs and it
can
be easily extended to support new services and functions.

But, before SMC is forwarded to standard SMCCC handler, it can be
routed
to a domain monitor, if one is installed.

Signed-off-by: Volodymyr Babchuk 
Reviewed-by: Oleksandr Andrushchenko

Reviewed-by: Oleksandr Tyshchenko 
---
 - Updated description to indicate that this patch affects only SMC
call path.
 - added "xen_" prefix to definitions in
include/public/arch-arm/smc.h
 - moved do_trap_smc() into vsmc.c from traps.c
 - replaced all tabs with spaces


I would have really appreciated a summary of the discussion we had on
the previous version regarding the bindings. This is a real blocker
for this series and should not be ignored.



While I agree that question about bindings is important, I can't
see how
it affects this patch series. This patch series does not break
anything.
Because

1. This series add only new feature: generic hypervisor service
with no
immediate use. All ARM guests are already aware that they are
running on
XEN. All ARM guests know that they call *only* PSCI.

2. I see importance of this patch series for embedded platforms, where
developer exactly knows what software of which version he/she will
run.
I doubt that server platforms will need something beyond PSCI, which I
preserved as is.


I disagree here. SMCCC could be used to provide Dom0 a way to interact
with the firmware if necessary.

AFAIK, Dom0 usually is built with particular version of XEN in mind (or
at least minimal XEN version).


That's not true. Dom0 is a generic kernel able to probe everything
from the firmware tables and Xen interface. I use the exact Linux
kernel on multiple platforms with no issue.

Okay, I was speaking about embedded use case.


Bear in mind that Xen is not only embedded. When you upstream a new 
feature you have to think about how this could be used by anyone.





The Hypervisor and Dom0 (Linux, FreeBSD) are different projects with
different release cadence. We provide a stable interface that is
backward compatible (returning error code for non-existent
hypercalls). So a Linux released in 10 years should still work on Xen
4.10 and adapt to the features available.

I just want to clarify this. At least four hypercalls are not backward
compatible: platform_op, sysctl, domctl and flask_op. I had a problem
with this, when played with MiniOS-based monitor. Sure, your kernel will
boot up, but some well known XEN services will be absent.
This have nothing with SMC bindings problem, though.


I am not sure to follow here... Were they ever be supported on ARM? If 
not, then it is no a backward compatibility issue. You cannot assume 
that all the hypercalls existing on x86 will be available on ARM.


For a list of known available/supported hypercalls for ARM see:
public/include/arch-arm.h.

Also bear in mind that some hypercalls are not part of the stable ABI. 
For instance domctls are not stable and it is well-known that you have 
to rebuild your app for every new Xen versions...


But domctls will never be used in Linux Kernel as they only meant to be 
used to control a domain.








A I'm not denying importance of SMC bindings, but I think it is not
blocker for my patches. We can add bindings later, when there will be
consensus on how they should look. In meantime SMC handler can be used
by anyone who knows that is available.


I am not in favor on getting something merged in Xen until we agree on
the way for the guest to know it is there.

I think that SMC implementation will be the same, regardless the way we
can tell guest that it is available. At this time guests can safely
assume that SMCCC is not implemented in XEN. This wouldn't break

Re: [Xen-devel] [PATCH 4/7] arm: smccc: handle SMCs according to SMCCC

[Volodymyr Babchuk]

Hi,

On 10.08.17 21:18, Julien Grall wrote:

Hi,

On 10/08/17 18:40, Volodymyr Babchuk wrote:



On 10.08.17 19:11, Julien Grall wrote:



On 10/08/17 16:33, Volodymyr Babchuk wrote:

Hi Julien,

On 09.08.17 13:10, Julien Grall wrote:

Hi Volodymyr,

CC "THE REST" maintainers to get an opinion on the public headers.

On 08/08/17 21:08, Volodymyr Babchuk wrote:

SMCCC (SMC Call Convention) describes how to handle both HVCs and
SMCs.
SMCCC states that both HVC and SMC are valid conduits to call to a
different
firmware functions. Thus, for example PSCI calls can be made both by
SMC or HVC. Also SMCCC defines function number coding for such calls.
Besides functional calls there are query calls, which allows 
underling

OS determine version, UID and number of functions provided by service
provider.

This patch adds new file `vsmc.c`, which handles both generic SMCs
and HVC according to SMC. At this moment it implements only one
service: Standard Hypervisor Service.

Standard Hypervisor Service only supports query calls, so caller can
ask about hypervisor UID and determine that it is XEN running.

This change allows more generic handling for SMCs and HVCs and it can
be easily extended to support new services and functions.

But, before SMC is forwarded to standard SMCCC handler, it can be
routed
to a domain monitor, if one is installed.

Signed-off-by: Volodymyr Babchuk 
Reviewed-by: Oleksandr Andrushchenko

Reviewed-by: Oleksandr Tyshchenko 
---
 - Updated description to indicate that this patch affects only SMC
call path.
 - added "xen_" prefix to definitions in 
include/public/arch-arm/smc.h

 - moved do_trap_smc() into vsmc.c from traps.c
 - replaced all tabs with spaces


I would have really appreciated a summary of the discussion we had on
the previous version regarding the bindings. This is a real blocker
for this series and should not be ignored.



While I agree that question about bindings is important, I can't see 
how
it affects this patch series. This patch series does not break 
anything.

Because

1. This series add only new feature: generic hypervisor service with no
immediate use. All ARM guests are already aware that they are 
running on

XEN. All ARM guests know that they call *only* PSCI.

2. I see importance of this patch series for embedded platforms, where
developer exactly knows what software of which version he/she will run.
I doubt that server platforms will need something beyond PSCI, which I
preserved as is.


I disagree here. SMCCC could be used to provide Dom0 a way to interact
with the firmware if necessary.

AFAIK, Dom0 usually is built with particular version of XEN in mind (or
at least minimal XEN version).


That's not true. Dom0 is a generic kernel able to probe everything from 
the firmware tables and Xen interface. I use the exact Linux kernel on 
multiple platforms with no issue.

Okay, I was speaking about embedded use case.

The Hypervisor and Dom0 (Linux, FreeBSD) are different projects with 
different release cadence. We provide a stable interface that is 
backward compatible (returning error code for non-existent hypercalls). 
So a Linux released in 10 years should still work on Xen 4.10 and adapt 
to the features available.
I just want to clarify this. At least four hypercalls are not backward 
compatible: platform_op, sysctl, domctl and flask_op. I had a problem 
with this, when played with MiniOS-based monitor. Sure, your kernel will 
boot up, but some well known XEN services will be absent.

This have nothing with SMC bindings problem, though.





A I'm not denying importance of SMC bindings, but I think it is not
blocker for my patches. We can add bindings later, when there will be
consensus on how they should look. In meantime SMC handler can be used
by anyone who knows that is available.


I am not in favor on getting something merged in Xen until we agree on
the way for the guest to know it is there.

I think that SMC implementation will be the same, regardless the way we
can tell guest that it is available. At this time guests can safely
assume that SMCCC is not implemented in XEN. This wouldn't break 
anything.


So you suggest to merge this series but says "The guest should not 
assume the presence of SMC"? This is rather a bit odd...
Basically yes. This is one of the options. If guest knowns for sure that 
SMCCC is available - it can use it. If it is unsure - then it does not 
use it.
In meantime we can develop a generic way to tell guest that SMCCC is 
present on a platform.
I just don't want to bloat up this patch series. There are already 7 
patches and looks like there will be more.
But I can add another patch/two with bindings if you insist. This is not 
a big deal. I just have concerns about this right now.





It means you have to carry hack in your kernel in order to use SMC.
Maybe this is fine for you, but I don't want to make this assumption
on Xen 

Re: [Xen-devel] [PATCH 4/7] arm: smccc: handle SMCs according to SMCCC

[Julien Grall]

Hi,

On 10/08/17 18:40, Volodymyr Babchuk wrote:



On 10.08.17 19:11, Julien Grall wrote:



On 10/08/17 16:33, Volodymyr Babchuk wrote:

Hi Julien,

On 09.08.17 13:10, Julien Grall wrote:

Hi Volodymyr,

CC "THE REST" maintainers to get an opinion on the public headers.

On 08/08/17 21:08, Volodymyr Babchuk wrote:

SMCCC (SMC Call Convention) describes how to handle both HVCs and
SMCs.
SMCCC states that both HVC and SMC are valid conduits to call to a
different
firmware functions. Thus, for example PSCI calls can be made both by
SMC or HVC. Also SMCCC defines function number coding for such calls.
Besides functional calls there are query calls, which allows underling
OS determine version, UID and number of functions provided by service
provider.

This patch adds new file `vsmc.c`, which handles both generic SMCs
and HVC according to SMC. At this moment it implements only one
service: Standard Hypervisor Service.

Standard Hypervisor Service only supports query calls, so caller can
ask about hypervisor UID and determine that it is XEN running.

This change allows more generic handling for SMCs and HVCs and it can
be easily extended to support new services and functions.

But, before SMC is forwarded to standard SMCCC handler, it can be
routed
to a domain monitor, if one is installed.

Signed-off-by: Volodymyr Babchuk 
Reviewed-by: Oleksandr Andrushchenko

Reviewed-by: Oleksandr Tyshchenko 
---
 - Updated description to indicate that this patch affects only SMC
call path.
 - added "xen_" prefix to definitions in include/public/arch-arm/smc.h
 - moved do_trap_smc() into vsmc.c from traps.c
 - replaced all tabs with spaces


I would have really appreciated a summary of the discussion we had on
the previous version regarding the bindings. This is a real blocker
for this series and should not be ignored.



While I agree that question about bindings is important, I can't see how
it affects this patch series. This patch series does not break anything.
Because

1. This series add only new feature: generic hypervisor service with no
immediate use. All ARM guests are already aware that they are running on
XEN. All ARM guests know that they call *only* PSCI.

2. I see importance of this patch series for embedded platforms, where
developer exactly knows what software of which version he/she will run.
I doubt that server platforms will need something beyond PSCI, which I
preserved as is.


I disagree here. SMCCC could be used to provide Dom0 a way to interact
with the firmware if necessary.

AFAIK, Dom0 usually is built with particular version of XEN in mind (or
at least minimal XEN version).


That's not true. Dom0 is a generic kernel able to probe everything from 
the firmware tables and Xen interface. I use the exact Linux kernel on 
multiple platforms with no issue.


The Hypervisor and Dom0 (Linux, FreeBSD) are different projects with 
different release cadence. We provide a stable interface that is 
backward compatible (returning error code for non-existent hypercalls). 
So a Linux released in 10 years should still work on Xen 4.10 and adapt 
to the features available.






A I'm not denying importance of SMC bindings, but I think it is not
blocker for my patches. We can add bindings later, when there will be
consensus on how they should look. In meantime SMC handler can be used
by anyone who knows that is available.


I am not in favor on getting something merged in Xen until we agree on
the way for the guest to know it is there.

I think that SMC implementation will be the same, regardless the way we
can tell guest that it is available. At this time guests can safely
assume that SMCCC is not implemented in XEN. This wouldn't break anything.


So you suggest to merge this series but says "The guest should not 
assume the presence of SMC"? This is rather a bit odd...





It means you have to carry hack in your kernel in order to use SMC.
Maybe this is fine for you, but I don't want to make this assumption
on Xen upstream today.

Modern linux kernel uses SMC for PSCI calls and OP-TEE calls. In both
cases it reads DT to get conduit method (SMC/HVC). So there are already
bindings for generic uses. Other uses are platform-specific (okay,
probably there can be a problem).


This is a change in the interface that should be notified to the
guest. If we expose it without providing a bindings (or something), we
have no way to revert/disable it. Imagine we want to disable SMC in
the future.

Natural way was to disable Security Extensions in PFR1 register. This
was not done and now we have curious situation: guest thinks that SMC is
available, but then it gets Undefined Instruction exception when it
tries to invoke SMC.


Security extensions does not mean that SMCCC is present... Even if we 
had returned an error, you don't know if it was from the SMCCC protocol 
or my foo protocol.


It would be valid (though a bit odd) for a 

Re: [Xen-devel] [PATCH 4/7] arm: smccc: handle SMCs according to SMCCC

[Volodymyr Babchuk]

On 10.08.17 19:11, Julien Grall wrote:



On 10/08/17 16:33, Volodymyr Babchuk wrote:

Hi Julien,

On 09.08.17 13:10, Julien Grall wrote:

Hi Volodymyr,

CC "THE REST" maintainers to get an opinion on the public headers.

On 08/08/17 21:08, Volodymyr Babchuk wrote:

SMCCC (SMC Call Convention) describes how to handle both HVCs and SMCs.
SMCCC states that both HVC and SMC are valid conduits to call to a
different
firmware functions. Thus, for example PSCI calls can be made both by
SMC or HVC. Also SMCCC defines function number coding for such calls.
Besides functional calls there are query calls, which allows underling
OS determine version, UID and number of functions provided by service
provider.

This patch adds new file `vsmc.c`, which handles both generic SMCs
and HVC according to SMC. At this moment it implements only one
service: Standard Hypervisor Service.

Standard Hypervisor Service only supports query calls, so caller can
ask about hypervisor UID and determine that it is XEN running.

This change allows more generic handling for SMCs and HVCs and it can
be easily extended to support new services and functions.

But, before SMC is forwarded to standard SMCCC handler, it can be 
routed

to a domain monitor, if one is installed.

Signed-off-by: Volodymyr Babchuk 
Reviewed-by: Oleksandr Andrushchenko 
Reviewed-by: Oleksandr Tyshchenko 
---
 - Updated description to indicate that this patch affects only SMC
call path.
 - added "xen_" prefix to definitions in include/public/arch-arm/smc.h
 - moved do_trap_smc() into vsmc.c from traps.c
 - replaced all tabs with spaces


I would have really appreciated a summary of the discussion we had on
the previous version regarding the bindings. This is a real blocker
for this series and should not be ignored.



While I agree that question about bindings is important, I can't see how
it affects this patch series. This patch series does not break anything.
Because

1. This series add only new feature: generic hypervisor service with no
immediate use. All ARM guests are already aware that they are running on
XEN. All ARM guests know that they call *only* PSCI.

2. I see importance of this patch series for embedded platforms, where
developer exactly knows what software of which version he/she will run.
I doubt that server platforms will need something beyond PSCI, which I
preserved as is.


I disagree here. SMCCC could be used to provide Dom0 a way to interact 
with the firmware if necessary.
AFAIK, Dom0 usually is built with particular version of XEN in mind (or 
at least minimal XEN version).




A I'm not denying importance of SMC bindings, but I think it is not
blocker for my patches. We can add bindings later, when there will be
consensus on how they should look. In meantime SMC handler can be used
by anyone who knows that is available.


I am not in favor on getting something merged in Xen until we agree on 
the way for the guest to know it is there. 
I think that SMC implementation will be the same, regardless the way we 
can tell guest that it is available. At this time guests can safely 
assume that SMCCC is not implemented in XEN. This wouldn't break anything.


It means you have to carry 
hack in your kernel in order to use SMC. Maybe this is fine for you, but 
I don't want to make this assumption on Xen upstream today.
Modern linux kernel uses SMC for PSCI calls and OP-TEE calls. In both 
cases it reads DT to get conduit method (SMC/HVC). So there are already 
bindings for generic uses. Other uses are platform-specific (okay, 
probably there can be a problem).


This is a change in the interface that should be notified to the guest. 
If we expose it without providing a bindings (or something), we have no 
way to revert/disable it. Imagine we want to disable SMC in the future. 
Natural way was to disable Security Extensions in PFR1 register. This 
was not done and now we have curious situation: guest thinks that SMC is 
available, but then it gets Undefined Instruction exception when it 
tries to invoke SMC.



How a guest will know that
 - until Xen 4.10 SMC was not existing,
 - between Xen 4.10 and Xen 4.x you can use them
 - after Xen 4.y they can be disabled.
It is a broader question: how software can know that SMCCC is available 
on a platform? Not SMC, but SMCCC as a protocol. Probably, there should 
be some generic way to tell Linux/Windows/XEN/Windriver Hypervisor/etc 
that they can rely on SMCCC spec. I think that it is question to ARM 
guys (including you), because this affects all ARM machines.


All changes should be detected through the firmware tables (DT, ACPI) or 
another Xen method (i.e XENFEAT_*). For instance, the guest has to parse 
the firmware tables in order to know PSCI is available.
Yep. The same does OP-TEE code. It parses DT to get conduit. Probably, 
this is wrong approach. Should all SMCCC calls use the same conduit?. 

Re: [Xen-devel] [PATCH 4/7] arm: smccc: handle SMCs according to SMCCC

[Julien Grall]

On 10/08/17 16:33, Volodymyr Babchuk wrote:

Hi Julien,

On 09.08.17 13:10, Julien Grall wrote:

Hi Volodymyr,

CC "THE REST" maintainers to get an opinion on the public headers.

On 08/08/17 21:08, Volodymyr Babchuk wrote:

SMCCC (SMC Call Convention) describes how to handle both HVCs and SMCs.
SMCCC states that both HVC and SMC are valid conduits to call to a
different
firmware functions. Thus, for example PSCI calls can be made both by
SMC or HVC. Also SMCCC defines function number coding for such calls.
Besides functional calls there are query calls, which allows underling
OS determine version, UID and number of functions provided by service
provider.

This patch adds new file `vsmc.c`, which handles both generic SMCs
and HVC according to SMC. At this moment it implements only one
service: Standard Hypervisor Service.

Standard Hypervisor Service only supports query calls, so caller can
ask about hypervisor UID and determine that it is XEN running.

This change allows more generic handling for SMCs and HVCs and it can
be easily extended to support new services and functions.

But, before SMC is forwarded to standard SMCCC handler, it can be routed
to a domain monitor, if one is installed.

Signed-off-by: Volodymyr Babchuk 
Reviewed-by: Oleksandr Andrushchenko 
Reviewed-by: Oleksandr Tyshchenko 
---
 - Updated description to indicate that this patch affects only SMC
call path.
 - added "xen_" prefix to definitions in include/public/arch-arm/smc.h
 - moved do_trap_smc() into vsmc.c from traps.c
 - replaced all tabs with spaces


I would have really appreciated a summary of the discussion we had on
the previous version regarding the bindings. This is a real blocker
for this series and should not be ignored.



While I agree that question about bindings is important, I can't see how
it affects this patch series. This patch series does not break anything.
Because

1. This series add only new feature: generic hypervisor service with no
immediate use. All ARM guests are already aware that they are running on
XEN. All ARM guests know that they call *only* PSCI.

2. I see importance of this patch series for embedded platforms, where
developer exactly knows what software of which version he/she will run.
I doubt that server platforms will need something beyond PSCI, which I
preserved as is.


I disagree here. SMCCC could be used to provide Dom0 a way to interact 
with the firmware if necessary.




A I'm not denying importance of SMC bindings, but I think it is not
blocker for my patches. We can add bindings later, when there will be
consensus on how they should look. In meantime SMC handler can be used
by anyone who knows that is available.


I am not in favor on getting something merged in Xen until we agree on 
the way for the guest to know it is there. It means you have to carry 
hack in your kernel in order to use SMC. Maybe this is fine for you, but 
I don't want to make this assumption on Xen upstream today.


This is a change in the interface that should be notified to the guest. 
If we expose it without providing a bindings (or something), we have no 
way to revert/disable it. Imagine we want to disable SMC in the future. 
How a guest will know that

- until Xen 4.10 SMC was not existing,
- between Xen 4.10 and Xen 4.x you can use them
- after Xen 4.y they can be disabled.

All changes should be detected through the firmware tables (DT, ACPI) or 
another Xen method (i.e XENFEAT_*). For instance, the guest has to parse 
the firmware tables in order to know PSCI is available.


Cheers,

--
Julien Grall

___
Xen-devel mailing list
Xen-devel@lists.xen.org
https://lists.xen.org/xen-devel

Re: [Xen-devel] [PATCH 4/7] arm: smccc: handle SMCs according to SMCCC

[Volodymyr Babchuk]

Hi Julien,

On 09.08.17 13:10, Julien Grall wrote:

Hi Volodymyr,

CC "THE REST" maintainers to get an opinion on the public headers.

On 08/08/17 21:08, Volodymyr Babchuk wrote:

SMCCC (SMC Call Convention) describes how to handle both HVCs and SMCs.
SMCCC states that both HVC and SMC are valid conduits to call to a 
different

firmware functions. Thus, for example PSCI calls can be made both by
SMC or HVC. Also SMCCC defines function number coding for such calls.
Besides functional calls there are query calls, which allows underling
OS determine version, UID and number of functions provided by service
provider.

This patch adds new file `vsmc.c`, which handles both generic SMCs
and HVC according to SMC. At this moment it implements only one
service: Standard Hypervisor Service.

Standard Hypervisor Service only supports query calls, so caller can
ask about hypervisor UID and determine that it is XEN running.

This change allows more generic handling for SMCs and HVCs and it can
be easily extended to support new services and functions.

But, before SMC is forwarded to standard SMCCC handler, it can be routed
to a domain monitor, if one is installed.

Signed-off-by: Volodymyr Babchuk 
Reviewed-by: Oleksandr Andrushchenko 
Reviewed-by: Oleksandr Tyshchenko 
---
 - Updated description to indicate that this patch affects only SMC 
call path.

 - added "xen_" prefix to definitions in include/public/arch-arm/smc.h
 - moved do_trap_smc() into vsmc.c from traps.c
 - replaced all tabs with spaces


I would have really appreciated a summary of the discussion we had on 
the previous version regarding the bindings. This is a real blocker for 
this series and should not be ignored.




While I agree that question about bindings is important, I can't see how 
it affects this patch series. This patch series does not break anything.

Because

1. This series add only new feature: generic hypervisor service with no 
immediate use. All ARM guests are already aware that they are running on 
XEN. All ARM guests know that they call *only* PSCI.


2. I see importance of this patch series for embedded platforms, where 
developer exactly knows what software of which version he/she will run. 
I doubt that server platforms will need something beyond PSCI, which I 
preserved as is.


A I'm not denying importance of SMC bindings, but I think it is not 
blocker for my patches. We can add bindings later, when there will be 
consensus on how they should look. In meantime SMC handler can be used 
by anyone who knows that is available.


___
Xen-devel mailing list
Xen-devel@lists.xen.org
https://lists.xen.org/xen-devel

Re: [Xen-devel] [PATCH 4/7] arm: smccc: handle SMCs according to SMCCC

[Julien Grall]

Hi,

On 10/08/17 08:30, Jan Beulich wrote:

On 09.08.17 at 23:39,  wrote:

On 09.08.17 14:58, Jan Beulich wrote:

On 09.08.17 at 12:10,  wrote:

On 08/08/17 21:08, Volodymyr Babchuk wrote:

+#ifndef __XEN_PUBLIC_ARCH_ARM_SMC_H__
+#define __XEN_PUBLIC_ARCH_ARM_SMC_H__
+
+typedef struct {
+uint32_t a[4];
+} xen_arm_smccc_uid;


This is not the normal way of encoding a UID type.

Just to be clear: you are proposing to store UID in such struct
struct uuid_t {
 unsigned32  time_low;
 unsigned16  time_mid;
 unsigned16  time_hi_and_version;
 unsigned8   clock_seq_hi_and_reserved;
 unsigned8   clock_seq_low;
 bytenode[6];
};
right?


Type-wise yes; the names of the fields look uncommon to me.


+#define XEN_ARM_SMCCC_UID(a, b, c, d0, d1, d2, d3, d4, d5, d6, d7)  \
+((xen_arm_smccc_uid) {{(a), ((b) << 16 | (c) ), \


This is not C89 compatible.

Oops, sorry. Didn't knew that XEN should be C89 compatible.
Is there any guide for novices? I didn't found anything useful in docs/
(not even coding style document). On wiki I have found only
"Submitting_Xen_Project_Patches" page, which is very helpful, but it
does not cover topics like which C standard to use.


The public headers are required to the C89 compatible; Xen
code in general is fine to use extensions.


+((d0) << 24 | (d1) << 16 | (d2) << 8 | (d3) << 0),  \
+((d4) << 24 | (d5) << 16 | (d6) << 8 | (d7) << 0)}})
+
+/*
+ * Hypervisor Service version.
+ *
+ * We can't use XEN version here, because of SMCCC requirements:
+ * Major revision should change every time SMC/HVC function is removed.
+ * Minor revision should change every time SMC/HVC function is added.
+ * So, it is SMCCC protocol revision code, not XEN version.


I don't understand this explanation - how is the situation here
different from some arbitrary, non-toolstack-only hypercall?

Because this is generic interface that should be supported by all
hypervisors, including XEN. Think about this as a way for a guest to
determine under which hypervisor it operates, and which functions it
provides.


In which case - why the XEN_ prefixes?


Because the version depends on the interface implemented which is Xen 
specific.


You have to match the UID (Xen Specific) and the version to know what is 
actually supported.


Cheers,

--
Julien Grall

___
Xen-devel mailing list
Xen-devel@lists.xen.org
https://lists.xen.org/xen-devel

Re: [Xen-devel] [PATCH 4/7] arm: smccc: handle SMCs according to SMCCC

[Jan Beulich]

>>> On 09.08.17 at 23:39,  wrote:
> On 09.08.17 14:58, Jan Beulich wrote:
> On 09.08.17 at 12:10,  wrote:
>>> On 08/08/17 21:08, Volodymyr Babchuk wrote:
 +#ifndef __XEN_PUBLIC_ARCH_ARM_SMC_H__
 +#define __XEN_PUBLIC_ARCH_ARM_SMC_H__
 +
 +typedef struct {
 +uint32_t a[4];
 +} xen_arm_smccc_uid;
>> 
>> This is not the normal way of encoding a UID type.
> Just to be clear: you are proposing to store UID in such struct
> struct uuid_t {
>  unsigned32  time_low;
>  unsigned16  time_mid;
>  unsigned16  time_hi_and_version;
>  unsigned8   clock_seq_hi_and_reserved;
>  unsigned8   clock_seq_low;
>  bytenode[6];
> };
> right?

Type-wise yes; the names of the fields look uncommon to me.

 +#define XEN_ARM_SMCCC_UID(a, b, c, d0, d1, d2, d3, d4, d5, d6, d7)  \
 +((xen_arm_smccc_uid) {{(a), ((b) << 16 | (c) ), \
>>
>> This is not C89 compatible.
> Oops, sorry. Didn't knew that XEN should be C89 compatible.
> Is there any guide for novices? I didn't found anything useful in docs/ 
> (not even coding style document). On wiki I have found only 
> "Submitting_Xen_Project_Patches" page, which is very helpful, but it 
> does not cover topics like which C standard to use.

The public headers are required to the C89 compatible; Xen
code in general is fine to use extensions.

 +((d0) << 24 | (d1) << 16 | (d2) << 8 | (d3) << 0),  \
 +((d4) << 24 | (d5) << 16 | (d6) << 8 | (d7) << 0)}})
 +
 +/*
 + * Hypervisor Service version.
 + *
 + * We can't use XEN version here, because of SMCCC requirements:
 + * Major revision should change every time SMC/HVC function is removed.
 + * Minor revision should change every time SMC/HVC function is added.
 + * So, it is SMCCC protocol revision code, not XEN version.
>> 
>> I don't understand this explanation - how is the situation here
>> different from some arbitrary, non-toolstack-only hypercall?
> Because this is generic interface that should be supported by all 
> hypervisors, including XEN. Think about this as a way for a guest to 
> determine under which hypervisor it operates, and which functions it 
> provides.

In which case - why the XEN_ prefixes?

Jan


___
Xen-devel mailing list
Xen-devel@lists.xen.org
https://lists.xen.org/xen-devel

Re: [Xen-devel] [PATCH 4/7] arm: smccc: handle SMCs according to SMCCC

[Volodymyr Babchuk]

On 09.08.17 14:58, Jan Beulich wrote:

On 09.08.17 at 12:10,  wrote:

CC "THE REST" maintainers to get an opinion on the public headers.


Please be more specific as to what you expect - the only public
header affected here is ARM-specific.


On 08/08/17 21:08, Volodymyr Babchuk wrote:

+#ifndef __XEN_PUBLIC_ARCH_ARM_SMC_H__
+#define __XEN_PUBLIC_ARCH_ARM_SMC_H__
+
+typedef struct {
+uint32_t a[4];
+} xen_arm_smccc_uid;


This is not the normal way of encoding a UID type.

Just to be clear: you are proposing to store UID in such struct
struct uuid_t {
unsigned32  time_low;
unsigned16  time_mid;
unsigned16  time_hi_and_version;
unsigned8   clock_seq_hi_and_reserved;
unsigned8   clock_seq_low;
bytenode[6];
};
right?



+#define XEN_ARM_SMCCC_UID(a, b, c, d0, d1, d2, d3, d4, d5, d6, d7)  \
+((xen_arm_smccc_uid) {{(a), ((b) << 16 | (c) ), \


This is not C89 compatible.

Oops, sorry. Didn't knew that XEN should be C89 compatible.
Is there any guide for novices? I didn't found anything useful in docs/ 
(not even coding style document). On wiki I have found only 
"Submitting_Xen_Project_Patches" page, which is very helpful, but it 
does not cover topics like which C standard to use.



+((d0) << 24 | (d1) << 16 | (d2) << 8 | (d3) << 0),  \
+((d4) << 24 | (d5) << 16 | (d6) << 8 | (d7) << 0)}})
+
+/*
+ * Hypervisor Service version.
+ *
+ * We can't use XEN version here, because of SMCCC requirements:
+ * Major revision should change every time SMC/HVC function is removed.
+ * Minor revision should change every time SMC/HVC function is added.
+ * So, it is SMCCC protocol revision code, not XEN version.


I don't understand this explanation - how is the situation here
different from some arbitrary, non-toolstack-only hypercall?
Because this is generic interface that should be supported by all 
hypervisors, including XEN. Think about this as a way for a guest to 
determine under which hypervisor it operates, and which functions it 
provides.



+ * Those values are subjected to change, when interface will be extended.
+ * They should not be stored in public/asm-arm/smc.h because they should
+ * be queried by guest using SMC/HVC interface.
+ */
+#define XEN_SMCCC_MAJOR_REVISION 0
+#define XEN_SMCCC_MINOR_REVISION 1


The comment says the values shouldn't be put here, but then
they're still being put here?

Yeah, sorry. Missed this.


+/* Hypervisor Service UID. Randomly generated with 3rd party tool.  */
+#define XEN_SMCCC_UID XEN_ARM_SMCCC_UID(0xa71812dc, 0xc698, 0x4369, \
+0x9a, 0xcf, 0x79, 0xd1, \
+0x8d, 0xde, 0xe6, 0x67)


Why is the right side using _ARM_ in its name, but the macro being
defined isn't?

Jan



___
Xen-devel mailing list
Xen-devel@lists.xen.org
https://lists.xen.org/xen-devel

Re: [Xen-devel] [PATCH 4/7] arm: smccc: handle SMCs according to SMCCC

[Jan Beulich]

>>> On 09.08.17 at 12:10,  wrote:
> CC "THE REST" maintainers to get an opinion on the public headers.

Please be more specific as to what you expect - the only public
header affected here is ARM-specific.

> On 08/08/17 21:08, Volodymyr Babchuk wrote:
>> +#ifndef __XEN_PUBLIC_ARCH_ARM_SMC_H__
>> +#define __XEN_PUBLIC_ARCH_ARM_SMC_H__
>> +
>> +typedef struct {
>> +uint32_t a[4];
>> +} xen_arm_smccc_uid;

This is not the normal way of encoding a UID type.

>> +#define XEN_ARM_SMCCC_UID(a, b, c, d0, d1, d2, d3, d4, d5, d6, d7)  \
>> +((xen_arm_smccc_uid) {{(a), ((b) << 16 | (c) ), \

This is not C89 compatible.

>> +((d0) << 24 | (d1) << 16 | (d2) << 8 | (d3) << 0),  \
>> +((d4) << 24 | (d5) << 16 | (d6) << 8 | (d7) << 0)}})
>> +
>> +/*
>> + * Hypervisor Service version.
>> + *
>> + * We can't use XEN version here, because of SMCCC requirements:
>> + * Major revision should change every time SMC/HVC function is removed.
>> + * Minor revision should change every time SMC/HVC function is added.
>> + * So, it is SMCCC protocol revision code, not XEN version.

I don't understand this explanation - how is the situation here
different from some arbitrary, non-toolstack-only hypercall?

>> + * Those values are subjected to change, when interface will be extended.
>> + * They should not be stored in public/asm-arm/smc.h because they should
>> + * be queried by guest using SMC/HVC interface.
>> + */
>> +#define XEN_SMCCC_MAJOR_REVISION 0
>> +#define XEN_SMCCC_MINOR_REVISION 1

The comment says the values shouldn't be put here, but then
they're still being put here?

>> +/* Hypervisor Service UID. Randomly generated with 3rd party tool.  */
>> +#define XEN_SMCCC_UID XEN_ARM_SMCCC_UID(0xa71812dc, 0xc698, 0x4369, \
>> +0x9a, 0xcf, 0x79, 0xd1, \
>> +0x8d, 0xde, 0xe6, 0x67)

Why is the right side using _ARM_ in its name, but the macro being
defined isn't?

Jan


___
Xen-devel mailing list
Xen-devel@lists.xen.org
https://lists.xen.org/xen-devel

Re: [Xen-devel] [PATCH 4/7] arm: smccc: handle SMCs according to SMCCC

[Julien Grall]

Hi Volodymyr,

CC "THE REST" maintainers to get an opinion on the public headers.

On 08/08/17 21:08, Volodymyr Babchuk wrote:

SMCCC (SMC Call Convention) describes how to handle both HVCs and SMCs.
SMCCC states that both HVC and SMC are valid conduits to call to a different
firmware functions. Thus, for example PSCI calls can be made both by
SMC or HVC. Also SMCCC defines function number coding for such calls.
Besides functional calls there are query calls, which allows underling
OS determine version, UID and number of functions provided by service
provider.

This patch adds new file `vsmc.c`, which handles both generic SMCs
and HVC according to SMC. At this moment it implements only one
service: Standard Hypervisor Service.

Standard Hypervisor Service only supports query calls, so caller can
ask about hypervisor UID and determine that it is XEN running.

This change allows more generic handling for SMCs and HVCs and it can
be easily extended to support new services and functions.

But, before SMC is forwarded to standard SMCCC handler, it can be routed
to a domain monitor, if one is installed.

Signed-off-by: Volodymyr Babchuk 
Reviewed-by: Oleksandr Andrushchenko 
Reviewed-by: Oleksandr Tyshchenko 
---
 - Updated description to indicate that this patch affects only SMC call path.
 - added "xen_" prefix to definitions in include/public/arch-arm/smc.h
 - moved do_trap_smc() into vsmc.c from traps.c
 - replaced all tabs with spaces


I would have really appreciated a summary of the discussion we had on 
the previous version regarding the bindings. This is a real blocker for 
this series and should not be ignored.




---
 xen/arch/arm/Makefile |   1 +
 xen/arch/arm/traps.c  |  19 +-
 xen/arch/arm/vsmc.c   | 139 ++
 xen/include/asm-arm/vsmc.h|  94 ++
 xen/include/public/arch-arm/smc.h |  68 +++
 5 files changed, 303 insertions(+), 18 deletions(-)
 create mode 100644 xen/arch/arm/vsmc.c
 create mode 100644 xen/include/asm-arm/vsmc.h
 create mode 100644 xen/include/public/arch-arm/smc.h

diff --git a/xen/arch/arm/Makefile b/xen/arch/arm/Makefile
index 49e1fb2..4efd01c 100644
--- a/xen/arch/arm/Makefile
+++ b/xen/arch/arm/Makefile
@@ -50,6 +50,7 @@ obj-$(CONFIG_HAS_GICV3) += vgic-v3.o
 obj-$(CONFIG_HAS_ITS) += vgic-v3-its.o
 obj-y += vm_event.o
 obj-y += vtimer.o
+obj-y += vsmc.o
 obj-y += vpsci.o
 obj-y += vuart.o

diff --git a/xen/arch/arm/traps.c b/xen/arch/arm/traps.c
index e14e7c0..b119dc0 100644
--- a/xen/arch/arm/traps.c
+++ b/xen/arch/arm/traps.c
@@ -43,7 +43,7 @@
 #include 
 #include 
 #include 
-#include 
+#include 

 #include "decode.h"
 #include "vtimer.h"
@@ -2769,23 +2769,6 @@ static void do_trap_data_abort_guest(struct 
cpu_user_regs *regs,
 inject_dabt_exception(regs, info.gva, hsr.len);
 }

-static void do_trap_smc(struct cpu_user_regs *regs, const union hsr hsr)
-{
-int rc = 0;
-
-if ( !check_conditional_instr(regs, hsr) )
-{
-advance_pc(regs, hsr);
-return;
-}
-
-if ( current->domain->arch.monitor.privileged_call_enabled )
-rc = monitor_smc();
-
-if ( rc != 1 )
-inject_undef_exception(regs, hsr);
-}
-
 static void enter_hypervisor_head(struct cpu_user_regs *regs)
 {
 if ( guest_mode(regs) )
diff --git a/xen/arch/arm/vsmc.c b/xen/arch/arm/vsmc.c
new file mode 100644
index 000..5ef6167
--- /dev/null
+++ b/xen/arch/arm/vsmc.c
@@ -0,0 +1,139 @@
+/*
+ * xen/arch/arm/vsmc.c
+ *
+ * Generic handler for SMC and HVC calls according to
+ * ARM SMC calling convention
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+
+
+#include 
+#include 
+#include 
+#include 
+#include 
+#include 


 should be before  to keep the headers ordered 
alphabetically.



+
+/* Number of functions currently supported by Hypervisor Service. */
+#define XEN_SMCCC_FUNCTION_COUNT 3
+
+/* SMCCC interface for hypervisor. Tell about itself. */
+static bool handle_hypervisor(struct cpu_user_regs *regs)
+{
+switch ( ARM_SMCCC_FUNC_NUM(get_user_reg(regs, 0)) )
+{
+case ARM_SMCCC_FUNC_CALL_COUNT:
+set_user_reg(regs, 0, XEN_SMCCC_FUNCTION_COUNT);
+return true;
+case ARM_SMCCC_FUNC_CALL_UID:
+set_user_reg(regs, 0, XEN_SMCCC_UID.a[0]);
+set_user_reg(regs, 1, XEN_SMCCC_UID.a[1]);
+set_user_reg(regs, 2, XEN_SMCCC_UID.a[2]);
+set_user_reg(regs, 3, XEN_SMCCC_UID.a[3]);
+return true;
+

[Xen-devel] [PATCH 4/7] arm: smccc: handle SMCs according to SMCCC

[Volodymyr Babchuk]

SMCCC (SMC Call Convention) describes how to handle both HVCs and SMCs.
SMCCC states that both HVC and SMC are valid conduits to call to a different
firmware functions. Thus, for example PSCI calls can be made both by
SMC or HVC. Also SMCCC defines function number coding for such calls.
Besides functional calls there are query calls, which allows underling
OS determine version, UID and number of functions provided by service
provider.

This patch adds new file `vsmc.c`, which handles both generic SMCs
and HVC according to SMC. At this moment it implements only one
service: Standard Hypervisor Service.

Standard Hypervisor Service only supports query calls, so caller can
ask about hypervisor UID and determine that it is XEN running.

This change allows more generic handling for SMCs and HVCs and it can
be easily extended to support new services and functions.

But, before SMC is forwarded to standard SMCCC handler, it can be routed
to a domain monitor, if one is installed.

Signed-off-by: Volodymyr Babchuk 
Reviewed-by: Oleksandr Andrushchenko 
Reviewed-by: Oleksandr Tyshchenko 
---
 - Updated description to indicate that this patch affects only SMC call path.
 - added "xen_" prefix to definitions in include/public/arch-arm/smc.h
 - moved do_trap_smc() into vsmc.c from traps.c
 - replaced all tabs with spaces

---
 xen/arch/arm/Makefile |   1 +
 xen/arch/arm/traps.c  |  19 +-
 xen/arch/arm/vsmc.c   | 139 ++
 xen/include/asm-arm/vsmc.h|  94 ++
 xen/include/public/arch-arm/smc.h |  68 +++
 5 files changed, 303 insertions(+), 18 deletions(-)
 create mode 100644 xen/arch/arm/vsmc.c
 create mode 100644 xen/include/asm-arm/vsmc.h
 create mode 100644 xen/include/public/arch-arm/smc.h

diff --git a/xen/arch/arm/Makefile b/xen/arch/arm/Makefile
index 49e1fb2..4efd01c 100644
--- a/xen/arch/arm/Makefile
+++ b/xen/arch/arm/Makefile
@@ -50,6 +50,7 @@ obj-$(CONFIG_HAS_GICV3) += vgic-v3.o
 obj-$(CONFIG_HAS_ITS) += vgic-v3-its.o
 obj-y += vm_event.o
 obj-y += vtimer.o
+obj-y += vsmc.o
 obj-y += vpsci.o
 obj-y += vuart.o
 
diff --git a/xen/arch/arm/traps.c b/xen/arch/arm/traps.c
index e14e7c0..b119dc0 100644
--- a/xen/arch/arm/traps.c
+++ b/xen/arch/arm/traps.c
@@ -43,7 +43,7 @@
 #include 
 #include 
 #include 
-#include 
+#include 
 
 #include "decode.h"
 #include "vtimer.h"
@@ -2769,23 +2769,6 @@ static void do_trap_data_abort_guest(struct 
cpu_user_regs *regs,
 inject_dabt_exception(regs, info.gva, hsr.len);
 }
 
-static void do_trap_smc(struct cpu_user_regs *regs, const union hsr hsr)
-{
-int rc = 0;
-
-if ( !check_conditional_instr(regs, hsr) )
-{
-advance_pc(regs, hsr);
-return;
-}
-
-if ( current->domain->arch.monitor.privileged_call_enabled )
-rc = monitor_smc();
-
-if ( rc != 1 )
-inject_undef_exception(regs, hsr);
-}
-
 static void enter_hypervisor_head(struct cpu_user_regs *regs)
 {
 if ( guest_mode(regs) )
diff --git a/xen/arch/arm/vsmc.c b/xen/arch/arm/vsmc.c
new file mode 100644
index 000..5ef6167
--- /dev/null
+++ b/xen/arch/arm/vsmc.c
@@ -0,0 +1,139 @@
+/*
+ * xen/arch/arm/vsmc.c
+ *
+ * Generic handler for SMC and HVC calls according to
+ * ARM SMC calling convention
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+
+
+#include 
+#include 
+#include 
+#include 
+#include 
+#include 
+
+/* Number of functions currently supported by Hypervisor Service. */
+#define XEN_SMCCC_FUNCTION_COUNT 3
+
+/* SMCCC interface for hypervisor. Tell about itself. */
+static bool handle_hypervisor(struct cpu_user_regs *regs)
+{
+switch ( ARM_SMCCC_FUNC_NUM(get_user_reg(regs, 0)) )
+{
+case ARM_SMCCC_FUNC_CALL_COUNT:
+set_user_reg(regs, 0, XEN_SMCCC_FUNCTION_COUNT);
+return true;
+case ARM_SMCCC_FUNC_CALL_UID:
+set_user_reg(regs, 0, XEN_SMCCC_UID.a[0]);
+set_user_reg(regs, 1, XEN_SMCCC_UID.a[1]);
+set_user_reg(regs, 2, XEN_SMCCC_UID.a[2]);
+set_user_reg(regs, 3, XEN_SMCCC_UID.a[3]);
+return true;
+case ARM_SMCCC_FUNC_CALL_REVISION:
+set_user_reg(regs, 0, XEN_SMCCC_MAJOR_REVISION);
+set_user_reg(regs, 1, XEN_SMCCC_MINOR_REVISION);
+return true;
+}
+return false;
+}
+
+/*
+ * vsmc_handle_call() - handle SMC/HVC call according to ARM SMCCC.
+ * returns true if that was valid SMCCC call (even if function number
+ * was unkown).
+ */
+static bool