Re: [Qemu-devel] [PATCH v2] hw/arm/virt-acpi - reserve ECAM space as PNP0C02 device

2017-01-19 Thread Peter Maydell 
On 18 January 2017 at 17:26, Laszlo Ersek  wrote:
> In brief, for one data point, I'd be fine if we didn't tie this change
> to machine types.

We seem to have arrived at a consensus that we don't need
to version-constrain this change, so I'm applying Ard's
patch to target-arm.next.

thanks
-- PMM

Re: [Qemu-devel] [PATCH v2] hw/arm/virt-acpi - reserve ECAM space as PNP0C02 device

2017-01-18 Thread Laszlo Ersek 
On 01/18/17 18:02, Ard Biesheuvel wrote:
> On 18 January 2017 at 15:55, Laszlo Ersek  wrote:
>> On 01/18/17 16:18, Igor Mammedov wrote:
>>> On Tue, 17 Jan 2017 10:56:53 +
>>> Peter Maydell  wrote:
>>>
 On 17 January 2017 at 09:49, Andrew Jones  wrote:
> In some cases the problem we're solving with the compat guards is
> a bit hypothetical, but, IMHO, nonetheless a good practice. While
> we may be sure that AAVMF and Linux will be fine with this table
> changing under their feet, we can't be sure there aren't other
> mach-virt users that have more sensitive firmwares/OSes. An ACPI-
> sensitive OS may notice the change on its next reboot after a
> migration, and then simply refuse to continue.

 There's also the case where you do a VM migration midway through
 UEFI booting up, I think, which might cause things to go wrong
 if you catch it just at the wrong moment.
>>> acpi blobs are migrated from source so above won't happen.
>>> The time guest will see new table is fresh boot or reboot.
>>>

> Now, that said, I just spoke with Igor in order to learn the x86
> practice. He says that the policy has been more lax than what I
> suggest above. Hypothetical, low-risk issues are left unguarded,
> and only when a bug is found during testing is it then managed.
> The idea is to try and reduce the amount of compat variables and
> conditions needed in the ACPI generation code, but, of course, at
> some level of risk to users expecting their versioned machine type
> to always appear the same.
>
> So far we've been strict with mach-virt, guarding all hypothetical
> issues. Perhaps this patch is a good example to get a discussion
> started on whether or not we should be so strict though.

 That said, I don't have a very strong opinion here, beyond that
 we should be consistent at least with x86 practice.
>>> another reason why we are trying not to use strict approach with ACPI
>>> tables is that it's part of firmware and we didn't version firmwares
>>> so far. (i.e. dst host with newer QEMU will typically have newer
>>> firmware and guest with old machine-type migrated to host with newer
>>> QEMU will run new firmware on (re)boot)
>>
>> I haven't been aware of this argument, and I'm surprised by it, but I
>> think it's valid. Regardless of our choice to ultimately compose the
>> ACPI tables in QEMU, guest OSes definitely consider ACPI as part of the
>> firmware. So, different ACPI content after a migration + guest reboot on
>> the target host is not much different from any other firmware-level
>> changes encountered on the same target host, after reboot.
>>
> 
> I agree. But does that imply that this fix should be tightly coupled
> to the mach-virt version, considering that the UEFI firmware you run
> *inside* such a vm is not versioned either?

No, it implies the exact opposite: given that the UEFI firmware is not
versioned, and may very well differ on source host and target host, the
ACPI payload that QEMU generates (and that the guest OS considers part
of the firmware) should be permitted to differ between src and dst host
just the same.

In brief, for one data point, I'd be fine if we didn't tie this change
to machine types.

Thanks
Laszlo

Re: [Qemu-devel] [PATCH v2] hw/arm/virt-acpi - reserve ECAM space as PNP0C02 device

2017-01-18 Thread Ard Biesheuvel 
On 18 January 2017 at 15:55, Laszlo Ersek  wrote:
> On 01/18/17 16:18, Igor Mammedov wrote:
>> On Tue, 17 Jan 2017 10:56:53 +
>> Peter Maydell  wrote:
>>
>>> On 17 January 2017 at 09:49, Andrew Jones  wrote:
 In some cases the problem we're solving with the compat guards is
 a bit hypothetical, but, IMHO, nonetheless a good practice. While
 we may be sure that AAVMF and Linux will be fine with this table
 changing under their feet, we can't be sure there aren't other
 mach-virt users that have more sensitive firmwares/OSes. An ACPI-
 sensitive OS may notice the change on its next reboot after a
 migration, and then simply refuse to continue.
>>>
>>> There's also the case where you do a VM migration midway through
>>> UEFI booting up, I think, which might cause things to go wrong
>>> if you catch it just at the wrong moment.
>> acpi blobs are migrated from source so above won't happen.
>> The time guest will see new table is fresh boot or reboot.
>>
>>>
 Now, that said, I just spoke with Igor in order to learn the x86
 practice. He says that the policy has been more lax than what I
 suggest above. Hypothetical, low-risk issues are left unguarded,
 and only when a bug is found during testing is it then managed.
 The idea is to try and reduce the amount of compat variables and
 conditions needed in the ACPI generation code, but, of course, at
 some level of risk to users expecting their versioned machine type
 to always appear the same.

 So far we've been strict with mach-virt, guarding all hypothetical
 issues. Perhaps this patch is a good example to get a discussion
 started on whether or not we should be so strict though.
>>>
>>> That said, I don't have a very strong opinion here, beyond that
>>> we should be consistent at least with x86 practice.
>> another reason why we are trying not to use strict approach with ACPI
>> tables is that it's part of firmware and we didn't version firmwares
>> so far. (i.e. dst host with newer QEMU will typically have newer
>> firmware and guest with old machine-type migrated to host with newer
>> QEMU will run new firmware on (re)boot)
>
> I haven't been aware of this argument, and I'm surprised by it, but I
> think it's valid. Regardless of our choice to ultimately compose the
> ACPI tables in QEMU, guest OSes definitely consider ACPI as part of the
> firmware. So, different ACPI content after a migration + guest reboot on
> the target host is not much different from any other firmware-level
> changes encountered on the same target host, after reboot.
>

I agree. But does that imply that this fix should be tightly coupled
to the mach-virt version, considering that the UEFI firmware you run
*inside* such a vm is not versioned either?

Re: [Qemu-devel] [PATCH v2] hw/arm/virt-acpi - reserve ECAM space as PNP0C02 device

2017-01-18 Thread Laszlo Ersek 
On 01/18/17 16:18, Igor Mammedov wrote:
> On Tue, 17 Jan 2017 10:56:53 +
> Peter Maydell  wrote:
> 
>> On 17 January 2017 at 09:49, Andrew Jones  wrote:
>>> In some cases the problem we're solving with the compat guards is
>>> a bit hypothetical, but, IMHO, nonetheless a good practice. While
>>> we may be sure that AAVMF and Linux will be fine with this table
>>> changing under their feet, we can't be sure there aren't other
>>> mach-virt users that have more sensitive firmwares/OSes. An ACPI-
>>> sensitive OS may notice the change on its next reboot after a
>>> migration, and then simply refuse to continue.  
>>
>> There's also the case where you do a VM migration midway through
>> UEFI booting up, I think, which might cause things to go wrong
>> if you catch it just at the wrong moment.
> acpi blobs are migrated from source so above won't happen.
> The time guest will see new table is fresh boot or reboot.
> 
>>
>>> Now, that said, I just spoke with Igor in order to learn the x86
>>> practice. He says that the policy has been more lax than what I
>>> suggest above. Hypothetical, low-risk issues are left unguarded,
>>> and only when a bug is found during testing is it then managed.
>>> The idea is to try and reduce the amount of compat variables and
>>> conditions needed in the ACPI generation code, but, of course, at
>>> some level of risk to users expecting their versioned machine type
>>> to always appear the same.
>>>
>>> So far we've been strict with mach-virt, guarding all hypothetical
>>> issues. Perhaps this patch is a good example to get a discussion
>>> started on whether or not we should be so strict though.  
>>
>> That said, I don't have a very strong opinion here, beyond that
>> we should be consistent at least with x86 practice.
> another reason why we are trying not to use strict approach with ACPI
> tables is that it's part of firmware and we didn't version firmwares
> so far. (i.e. dst host with newer QEMU will typically have newer
> firmware and guest with old machine-type migrated to host with newer
> QEMU will run new firmware on (re)boot)

I haven't been aware of this argument, and I'm surprised by it, but I
think it's valid. Regardless of our choice to ultimately compose the
ACPI tables in QEMU, guest OSes definitely consider ACPI as part of the
firmware. So, different ACPI content after a migration + guest reboot on
the target host is not much different from any other firmware-level
changes encountered on the same target host, after reboot.

Laszlo

Re: [Qemu-devel] [PATCH v2] hw/arm/virt-acpi - reserve ECAM space as PNP0C02 device

2017-01-18 Thread Igor Mammedov 
On Tue, 17 Jan 2017 10:56:53 +
Peter Maydell  wrote:

> On 17 January 2017 at 09:49, Andrew Jones  wrote:
> > In some cases the problem we're solving with the compat guards is
> > a bit hypothetical, but, IMHO, nonetheless a good practice. While
> > we may be sure that AAVMF and Linux will be fine with this table
> > changing under their feet, we can't be sure there aren't other
> > mach-virt users that have more sensitive firmwares/OSes. An ACPI-
> > sensitive OS may notice the change on its next reboot after a
> > migration, and then simply refuse to continue.  
> 
> There's also the case where you do a VM migration midway through
> UEFI booting up, I think, which might cause things to go wrong
> if you catch it just at the wrong moment.
acpi blobs are migrated from source so above won't happen.
The time guest will see new table is fresh boot or reboot.

> 
> > Now, that said, I just spoke with Igor in order to learn the x86
> > practice. He says that the policy has been more lax than what I
> > suggest above. Hypothetical, low-risk issues are left unguarded,
> > and only when a bug is found during testing is it then managed.
> > The idea is to try and reduce the amount of compat variables and
> > conditions needed in the ACPI generation code, but, of course, at
> > some level of risk to users expecting their versioned machine type
> > to always appear the same.
> >
> > So far we've been strict with mach-virt, guarding all hypothetical
> > issues. Perhaps this patch is a good example to get a discussion
> > started on whether or not we should be so strict though.  
> 
> That said, I don't have a very strong opinion here, beyond that
> we should be consistent at least with x86 practice.
another reason why we are trying not to use strict approach with ACPI
tables is that it's part of firmware and we didn't version firmwares
so far. (i.e. dst host with newer QEMU will typically have newer
firmware and guest with old machine-type migrated to host with newer
QEMU will run new firmware on (re)boot)

> 
> thanks
> -- PMM

Re: [Qemu-devel] [PATCH v2] hw/arm/virt-acpi - reserve ECAM space as PNP0C02 device

2017-01-18 Thread Ard Biesheuvel 
On 17 January 2017 at 09:49, Andrew Jones  wrote:
> On Mon, Jan 16, 2017 at 07:31:33PM +, Ard Biesheuvel wrote:
>> On 16 January 2017 at 18:20, Peter Maydell  wrote:
>> > On 16 January 2017 at 17:30, Ard Biesheuvel  
>> > wrote:
>> >> On 16 January 2017 at 17:25, Peter Maydell  
>> >> wrote:
>> >>> On 13 January 2017 at 17:32, Ard Biesheuvel  
>> >>> wrote:
>>  Linux for arm64 v4.10 and later will complain if the ECAM config space 
>>  is
>>  not reserved in the ACPI namespace:
>> 
>>    acpi PNP0A08:00: [Firmware Bug]: ECAM area [mem 
>>  0x3f00-0x3fff] not reserved in ACPI namespace
>> 
>>  The rationale is that OSes that don't consume the MCFG table should 
>>  still
>>  be able to infer that the PCI config space MMIO region is occupied.
>> 
>>  So update the ACPI table generation routine to add this reservation.
>> 
>>  Signed-off-by: Ard Biesheuvel 
>>  ---
>>   hw/arm/virt-acpi-build.c | 7 +++
>>   1 file changed, 7 insertions(+)
>> 
>>  diff --git a/hw/arm/virt-acpi-build.c b/hw/arm/virt-acpi-build.c
>>  index 085a61117378..50d52f685f68 100644
>>  --- a/hw/arm/virt-acpi-build.c
>>  +++ b/hw/arm/virt-acpi-build.c
>>  @@ -310,6 +310,13 @@ static void acpi_dsdt_add_pci(Aml *scope, const 
>>  MemMapEntry *memmap,
>>   Aml *dev_rp0 = aml_device("%s", "RP0");
>>   aml_append(dev_rp0, aml_name_decl("_ADR", aml_int(0)));
>>   aml_append(dev, dev_rp0);
>>  +
>>  +Aml *dev_res0 = aml_device("%s", "RES0");
>>  +aml_append(dev_res0, aml_name_decl("_HID", aml_string("PNP0C02")));
>>  +crs = aml_resource_template();
>>  +aml_append(crs, aml_memory32_fixed(base_ecam, size_ecam, 
>>  AML_READ_WRITE));
>>  +aml_append(dev_res0, aml_name_decl("_CRS", crs));
>>  +aml_append(dev, dev_res0);
>>   aml_append(scope, dev);
>>   }
>> >>>
>> >>> This needs to be controlled via the machine class back-compat
>> >>> machinery in hw/arm/virt.c so that it only happens for virt-2.9
>> >>> and later.
>> >>>
>> >>
>> >> Why exactly?
>> >
>> > Because the "virt-2.8" machine has to present to the guest
>> > exactly what "virt" did as of the QEMU 2.8 release, including
>> > any bugs or missing things we happened to have in our ACPI
>> > tables. This allows cross-version compatibility (including
>> > VM migration). Drew will have a more detailed explanation
>> > if you need it.
>> >
>>
>> I suspected as much.
>>
>> But in this case, I am not sure if it is worth the trouble: the
>> generated data is only consumed at boot time by the firmware, and I
>> suppose migration involves freezing a VM, including whatever resident
>> firmware image was used to boot the OS, and so this is unlikely to
>> affect migration.
>>
>> But I will let Drew explain ...
>>
>
> In some cases the problem we're solving with the compat guards is
> a bit hypothetical, but, IMHO, nonetheless a good practice. While
> we may be sure that AAVMF and Linux will be fine with this table
> changing under their feet, we can't be sure there aren't other
> mach-virt users that have more sensitive firmwares/OSes. An ACPI-
> sensitive OS may notice the change on its next reboot after a
> migration, and then simply refuse to continue.
>
> Now, that said, I just spoke with Igor in order to learn the x86
> practice. He says that the policy has been more lax than what I
> suggest above. Hypothetical, low-risk issues are left unguarded,
> and only when a bug is found during testing is it then managed.
> The idea is to try and reduce the amount of compat variables and
> conditions needed in the ACPI generation code, but, of course, at
> some level of risk to users expecting their versioned machine type
> to always appear the same.
>
> So far we've been strict with mach-virt, guarding all hypothetical
> issues. Perhaps this patch is a good example to get a discussion
> started on whether or not we should be so strict though.
>

Yes please. I don't mind respinning the patch, but I agree that it
makes sense to consider whether minimal bug fixes like this one
require this treatment in the first place

Re: [Qemu-devel] [PATCH v2] hw/arm/virt-acpi - reserve ECAM space as PNP0C02 device

2017-01-17 Thread Michael S. Tsirkin 
On Mon, Jan 16, 2017 at 11:35:04PM +0100, Laszlo Ersek wrote:
> On 01/16/17 22:23, Ard Biesheuvel wrote:
> > On 16 January 2017 at 21:13, Laszlo Ersek  wrote:
> >> On 01/16/17 20:31, Ard Biesheuvel wrote:
> >>> On 16 January 2017 at 18:20, Peter Maydell  
> >>> wrote:
>  On 16 January 2017 at 17:30, Ard Biesheuvel  
>  wrote:
> > On 16 January 2017 at 17:25, Peter Maydell  
> > wrote:
> >> On 13 January 2017 at 17:32, Ard Biesheuvel 
> >>  wrote:
> >>> Linux for arm64 v4.10 and later will complain if the ECAM config 
> >>> space is
> >>> not reserved in the ACPI namespace:
> >>>
> >>>   acpi PNP0A08:00: [Firmware Bug]: ECAM area [mem 
> >>> 0x3f00-0x3fff] not reserved in ACPI namespace
> >>>
> >>> The rationale is that OSes that don't consume the MCFG table should 
> >>> still
> >>> be able to infer that the PCI config space MMIO region is occupied.
> >>>
> >>> So update the ACPI table generation routine to add this reservation.
> >>>
> >>> Signed-off-by: Ard Biesheuvel 
> >>> ---
> >>>  hw/arm/virt-acpi-build.c | 7 +++
> >>>  1 file changed, 7 insertions(+)
> >>>
> >>> diff --git a/hw/arm/virt-acpi-build.c b/hw/arm/virt-acpi-build.c
> >>> index 085a61117378..50d52f685f68 100644
> >>> --- a/hw/arm/virt-acpi-build.c
> >>> +++ b/hw/arm/virt-acpi-build.c
> >>> @@ -310,6 +310,13 @@ static void acpi_dsdt_add_pci(Aml *scope, const 
> >>> MemMapEntry *memmap,
> >>>  Aml *dev_rp0 = aml_device("%s", "RP0");
> >>>  aml_append(dev_rp0, aml_name_decl("_ADR", aml_int(0)));
> >>>  aml_append(dev, dev_rp0);
> >>> +
> >>> +Aml *dev_res0 = aml_device("%s", "RES0");
> >>> +aml_append(dev_res0, aml_name_decl("_HID", 
> >>> aml_string("PNP0C02")));
> >>> +crs = aml_resource_template();
> >>> +aml_append(crs, aml_memory32_fixed(base_ecam, size_ecam, 
> >>> AML_READ_WRITE));
> >>> +aml_append(dev_res0, aml_name_decl("_CRS", crs));
> >>> +aml_append(dev, dev_res0);
> >>>  aml_append(scope, dev);
> >>>  }
> >>
> >> This needs to be controlled via the machine class back-compat
> >> machinery in hw/arm/virt.c so that it only happens for virt-2.9
> >> and later.
> >>
> >
> > Why exactly?
> 
>  Because the "virt-2.8" machine has to present to the guest
>  exactly what "virt" did as of the QEMU 2.8 release, including
>  any bugs or missing things we happened to have in our ACPI
>  tables. This allows cross-version compatibility (including
>  VM migration). Drew will have a more detailed explanation
>  if you need it.
> 
> >>>
> >>> I suspected as much.
> >>>
> >>> But in this case, I am not sure if it is worth the trouble: the
> >>> generated data is only consumed at boot time by the firmware, and I
> >>> suppose migration involves freezing a VM, including whatever resident
> >>> firmware image was used to boot the OS, and so this is unlikely to
> >>> affect migration.
> >>>
> >>> But I will let Drew explain ...
> >>
> >> The PCI Firmware Specification (rev 3.1) says in 4.1.2. "MCFG Table
> >> Description": "The resources can *optionally* be returned in [...]
> >> EFIGetMemoryMap as reserved memory [...]". (Emphasis mine.) Linux seems
> >> to *insist* on this kind of reservation however.
> >>
> > 
> > No, not at the UEFI level but at the ACPI level. Reservations in the
> > UEFI memory map describe memory not MMIO space
> > 
> >> PNP0C02 is "General ID for reserving resources required by PnP
> >> motherboard registers. (Not device specific.)", according to
> >> .
> >> So what this patch does is reserve a memory area through ACPI,
> >> practically as an unspecified "platform resource".
> >>
> > 
> > This has been discussed at great length on the linux mailing lists
> > 
> > https://patchwork.kernel.org/patch/9453149/
> > 
> >> There's an alternative that's contained entirely in the firmware. You
> >> can cover the MMCONFIG area in ArmVirtQemu with an EfiReservedMemoryType
> >> memory map entry (by producing an appropriate memalloc HOB in PEI, or by
> >> calling the appropriate gDS memory space map functions in DXE). OVMF
> >> does the former (memalloc HOB).
> >>
> >> In ArmVirtQemu, we grab the MMCONFIG range from "pci-host-ecam-generic",
> >> from QEMU's DTB. If you don't dislike the idea, we could cover the range
> >> as well, right in "ArmVirtPkg/Library/FdtPciPcdProducerLib". That lib
> >> instance already sets the base address PCD, and makes sure that the
> >> relevant code is executed only once (in whatever driver module the
> >> library instance was built into). You could call the gDS functions
> >> mentioned above from that

Re: [Qemu-devel] [PATCH v2] hw/arm/virt-acpi - reserve ECAM space as PNP0C02 device

2017-01-17 Thread Peter Maydell 
On 17 January 2017 at 09:49, Andrew Jones  wrote:
> In some cases the problem we're solving with the compat guards is
> a bit hypothetical, but, IMHO, nonetheless a good practice. While
> we may be sure that AAVMF and Linux will be fine with this table
> changing under their feet, we can't be sure there aren't other
> mach-virt users that have more sensitive firmwares/OSes. An ACPI-
> sensitive OS may notice the change on its next reboot after a
> migration, and then simply refuse to continue.

There's also the case where you do a VM migration midway through
UEFI booting up, I think, which might cause things to go wrong
if you catch it just at the wrong moment.

> Now, that said, I just spoke with Igor in order to learn the x86
> practice. He says that the policy has been more lax than what I
> suggest above. Hypothetical, low-risk issues are left unguarded,
> and only when a bug is found during testing is it then managed.
> The idea is to try and reduce the amount of compat variables and
> conditions needed in the ACPI generation code, but, of course, at
> some level of risk to users expecting their versioned machine type
> to always appear the same.
>
> So far we've been strict with mach-virt, guarding all hypothetical
> issues. Perhaps this patch is a good example to get a discussion
> started on whether or not we should be so strict though.

That said, I don't have a very strong opinion here, beyond that
we should be consistent at least with x86 practice.

thanks
-- PMM

Re: [Qemu-devel] [PATCH v2] hw/arm/virt-acpi - reserve ECAM space as PNP0C02 device

2017-01-17 Thread Laszlo Ersek 
On 01/17/17 10:06, Ard Biesheuvel wrote:
> On 17 January 2017 at 08:50, Laszlo Ersek  wrote:
>> (my reply is no longer related to the patch, so maybe I shouldn't send
>> it... I can't resist, sorry :))
>>
>> On 01/17/17 08:47, Ard Biesheuvel wrote:
>>> On 16 January 2017 at 22:35, Laszlo Ersek  wrote:
>>
 The UEFI memory map will reflect allocations from the GCD memory space,
 for the Reserved and MMIO types. See "Figure 2. GCD Memory State
 Transitions" in "7.2.2 GCD Memory Resources", Vol2 of the PI spec.

 See also "9.7.1 UEFI Boot Services Dependencies" in the same,

   9.7.1.8 GetMemoryMap()

   The GetMemoryMap() implementation must include into the UEFI memory
   map all GCD map entries of types EfiGcdMemoryTypeReserved and
   EfiPersistentMemory, and all GCD map entries of type
   EfiGcdMemoryTypeMemoryMappedIo that have EFI_MEMORY_RUNTIME attribute
   set.

 (Note that I wrote Reserved earlier, not MMIO.)

>>>
>>> What the PI spec stipulates is irrelevant: the contract between the
>>> firmware and the OS is in the UEFI and ACPI specifications, not in the
>>> PI spec.
>>
>> I disagree that what the PI spec stipulates is irrelevant. For platforms
>> that implement both PI and UEFI, the PI spec expresses additional
>> requirements for the UEFI implementation (in PI terminology). So what it
>> says certainly matters for the ArmVirtQemu firmware specifically.
>>
>> End-to-end, if we want to achieve a particular result in a UEFI OS, we
>> can certainly work towards that end in the PEI phase (or in the DXE
>> phase, using the DXE services) in a specific firmware that aims to
>> conform to both PI and UEFI. Because, the effects that those low-level
>> operations will have on the UEFI level (and consequently, on the OS) are
>> well defined in the PI spec.
>>
> 
> PI spec should drive the implementation choices we make at the
> ArmVirtQemu end, and the ACPI generation is tightly coupled with that,
> so in that sense, I agree that the PI spec *is* relevant.
> 
> However, the purpose of the patch (which we are no longer discussing
> :-)), is to ensure that QEMU + ArmVirtQemu adheres to the pertinent
> contracts with the OS, and PI is not one of them.
> 
>>>
 However, you are right that *just* the UEFI memmap entry is not
 sufficient, according to the PCI firmware spec. (Regardless of the fact
 that in practice, just the memmap entry does keep Linux happy. Or is it
 about to change?)

>>>
>>> The kernel uses the UEFI memory map for two purposes:
>>> - finding out where memory is, and which parts are usable (i.e., 
>>> non-reserved)
>>> - setting up page tables to allow UEFI runtime services calls, which
>>> may include MMIO mappings
>>>
>>> This means that MMIO regions in the UEFI memory map are *not*
>>> considered reservations. [...]
>>
>> Yes, I understand that. Now please understand that my suggestion was
>> never to cover the MMCONFIG area with MMIO type memory; all along I've
>> been saying "reserved memory".
>>
>> (Again, this is now independent of the patch.)
>>
> 
> I know the various specs are vague and slightly contradictory, but I
> would oppose to using EfiReservedMemory to describe an MMIO region,
> given that the wording of the UEFI spec (which is authoritative imo)
> suggests that the memory map should only describe memory (unless we
> are dealing with MMIO regions that require a runtime mapping so that
> the firmware can use the device while running under the OS)
> 

Fair enough, on both counts :)

Re: [Qemu-devel] [PATCH v2] hw/arm/virt-acpi - reserve ECAM space as PNP0C02 device

2017-01-17 Thread Andrew Jones 
On Mon, Jan 16, 2017 at 07:31:33PM +, Ard Biesheuvel wrote:
> On 16 January 2017 at 18:20, Peter Maydell  wrote:
> > On 16 January 2017 at 17:30, Ard Biesheuvel  
> > wrote:
> >> On 16 January 2017 at 17:25, Peter Maydell  
> >> wrote:
> >>> On 13 January 2017 at 17:32, Ard Biesheuvel  
> >>> wrote:
>  Linux for arm64 v4.10 and later will complain if the ECAM config space is
>  not reserved in the ACPI namespace:
> 
>    acpi PNP0A08:00: [Firmware Bug]: ECAM area [mem 0x3f00-0x3fff] 
>  not reserved in ACPI namespace
> 
>  The rationale is that OSes that don't consume the MCFG table should still
>  be able to infer that the PCI config space MMIO region is occupied.
> 
>  So update the ACPI table generation routine to add this reservation.
> 
>  Signed-off-by: Ard Biesheuvel 
>  ---
>   hw/arm/virt-acpi-build.c | 7 +++
>   1 file changed, 7 insertions(+)
> 
>  diff --git a/hw/arm/virt-acpi-build.c b/hw/arm/virt-acpi-build.c
>  index 085a61117378..50d52f685f68 100644
>  --- a/hw/arm/virt-acpi-build.c
>  +++ b/hw/arm/virt-acpi-build.c
>  @@ -310,6 +310,13 @@ static void acpi_dsdt_add_pci(Aml *scope, const 
>  MemMapEntry *memmap,
>   Aml *dev_rp0 = aml_device("%s", "RP0");
>   aml_append(dev_rp0, aml_name_decl("_ADR", aml_int(0)));
>   aml_append(dev, dev_rp0);
>  +
>  +Aml *dev_res0 = aml_device("%s", "RES0");
>  +aml_append(dev_res0, aml_name_decl("_HID", aml_string("PNP0C02")));
>  +crs = aml_resource_template();
>  +aml_append(crs, aml_memory32_fixed(base_ecam, size_ecam, 
>  AML_READ_WRITE));
>  +aml_append(dev_res0, aml_name_decl("_CRS", crs));
>  +aml_append(dev, dev_res0);
>   aml_append(scope, dev);
>   }
> >>>
> >>> This needs to be controlled via the machine class back-compat
> >>> machinery in hw/arm/virt.c so that it only happens for virt-2.9
> >>> and later.
> >>>
> >>
> >> Why exactly?
> >
> > Because the "virt-2.8" machine has to present to the guest
> > exactly what "virt" did as of the QEMU 2.8 release, including
> > any bugs or missing things we happened to have in our ACPI
> > tables. This allows cross-version compatibility (including
> > VM migration). Drew will have a more detailed explanation
> > if you need it.
> >
> 
> I suspected as much.
> 
> But in this case, I am not sure if it is worth the trouble: the
> generated data is only consumed at boot time by the firmware, and I
> suppose migration involves freezing a VM, including whatever resident
> firmware image was used to boot the OS, and so this is unlikely to
> affect migration.
> 
> But I will let Drew explain ...
>

In some cases the problem we're solving with the compat guards is
a bit hypothetical, but, IMHO, nonetheless a good practice. While
we may be sure that AAVMF and Linux will be fine with this table
changing under their feet, we can't be sure there aren't other
mach-virt users that have more sensitive firmwares/OSes. An ACPI-
sensitive OS may notice the change on its next reboot after a
migration, and then simply refuse to continue.

Now, that said, I just spoke with Igor in order to learn the x86
practice. He says that the policy has been more lax than what I
suggest above. Hypothetical, low-risk issues are left unguarded,
and only when a bug is found during testing is it then managed.
The idea is to try and reduce the amount of compat variables and
conditions needed in the ACPI generation code, but, of course, at
some level of risk to users expecting their versioned machine type
to always appear the same.

So far we've been strict with mach-virt, guarding all hypothetical
issues. Perhaps this patch is a good example to get a discussion
started on whether or not we should be so strict though.

Thanks,
drew

Re: [Qemu-devel] [PATCH v2] hw/arm/virt-acpi - reserve ECAM space as PNP0C02 device

2017-01-17 Thread Ard Biesheuvel 
On 17 January 2017 at 08:50, Laszlo Ersek  wrote:
> (my reply is no longer related to the patch, so maybe I shouldn't send
> it... I can't resist, sorry :))
>
> On 01/17/17 08:47, Ard Biesheuvel wrote:
>> On 16 January 2017 at 22:35, Laszlo Ersek  wrote:
>
>>> The UEFI memory map will reflect allocations from the GCD memory space,
>>> for the Reserved and MMIO types. See "Figure 2. GCD Memory State
>>> Transitions" in "7.2.2 GCD Memory Resources", Vol2 of the PI spec.
>>>
>>> See also "9.7.1 UEFI Boot Services Dependencies" in the same,
>>>
>>>   9.7.1.8 GetMemoryMap()
>>>
>>>   The GetMemoryMap() implementation must include into the UEFI memory
>>>   map all GCD map entries of types EfiGcdMemoryTypeReserved and
>>>   EfiPersistentMemory, and all GCD map entries of type
>>>   EfiGcdMemoryTypeMemoryMappedIo that have EFI_MEMORY_RUNTIME attribute
>>>   set.
>>>
>>> (Note that I wrote Reserved earlier, not MMIO.)
>>>
>>
>> What the PI spec stipulates is irrelevant: the contract between the
>> firmware and the OS is in the UEFI and ACPI specifications, not in the
>> PI spec.
>
> I disagree that what the PI spec stipulates is irrelevant. For platforms
> that implement both PI and UEFI, the PI spec expresses additional
> requirements for the UEFI implementation (in PI terminology). So what it
> says certainly matters for the ArmVirtQemu firmware specifically.
>
> End-to-end, if we want to achieve a particular result in a UEFI OS, we
> can certainly work towards that end in the PEI phase (or in the DXE
> phase, using the DXE services) in a specific firmware that aims to
> conform to both PI and UEFI. Because, the effects that those low-level
> operations will have on the UEFI level (and consequently, on the OS) are
> well defined in the PI spec.
>

PI spec should drive the implementation choices we make at the
ArmVirtQemu end, and the ACPI generation is tightly coupled with that,
so in that sense, I agree that the PI spec *is* relevant.

However, the purpose of the patch (which we are no longer discussing
:-)), is to ensure that QEMU + ArmVirtQemu adheres to the pertinent
contracts with the OS, and PI is not one of them.

>>
>>> However, you are right that *just* the UEFI memmap entry is not
>>> sufficient, according to the PCI firmware spec. (Regardless of the fact
>>> that in practice, just the memmap entry does keep Linux happy. Or is it
>>> about to change?)
>>>
>>
>> The kernel uses the UEFI memory map for two purposes:
>> - finding out where memory is, and which parts are usable (i.e., 
>> non-reserved)
>> - setting up page tables to allow UEFI runtime services calls, which
>> may include MMIO mappings
>>
>> This means that MMIO regions in the UEFI memory map are *not*
>> considered reservations. [...]
>
> Yes, I understand that. Now please understand that my suggestion was
> never to cover the MMCONFIG area with MMIO type memory; all along I've
> been saying "reserved memory".
>
> (Again, this is now independent of the patch.)
>

I know the various specs are vague and slightly contradictory, but I
would oppose to using EfiReservedMemory to describe an MMIO region,
given that the wording of the UEFI spec (which is authoritative imo)
suggests that the memory map should only describe memory (unless we
are dealing with MMIO regions that require a runtime mapping so that
the firmware can use the device while running under the OS)

Re: [Qemu-devel] [PATCH v2] hw/arm/virt-acpi - reserve ECAM space as PNP0C02 device

2017-01-17 Thread Laszlo Ersek 
(my reply is no longer related to the patch, so maybe I shouldn't send
it... I can't resist, sorry :))

On 01/17/17 08:47, Ard Biesheuvel wrote:
> On 16 January 2017 at 22:35, Laszlo Ersek  wrote:

>> The UEFI memory map will reflect allocations from the GCD memory space,
>> for the Reserved and MMIO types. See "Figure 2. GCD Memory State
>> Transitions" in "7.2.2 GCD Memory Resources", Vol2 of the PI spec.
>>
>> See also "9.7.1 UEFI Boot Services Dependencies" in the same,
>>
>>   9.7.1.8 GetMemoryMap()
>>
>>   The GetMemoryMap() implementation must include into the UEFI memory
>>   map all GCD map entries of types EfiGcdMemoryTypeReserved and
>>   EfiPersistentMemory, and all GCD map entries of type
>>   EfiGcdMemoryTypeMemoryMappedIo that have EFI_MEMORY_RUNTIME attribute
>>   set.
>>
>> (Note that I wrote Reserved earlier, not MMIO.)
>>
> 
> What the PI spec stipulates is irrelevant: the contract between the
> firmware and the OS is in the UEFI and ACPI specifications, not in the
> PI spec.

I disagree that what the PI spec stipulates is irrelevant. For platforms
that implement both PI and UEFI, the PI spec expresses additional
requirements for the UEFI implementation (in PI terminology). So what it
says certainly matters for the ArmVirtQemu firmware specifically.

End-to-end, if we want to achieve a particular result in a UEFI OS, we
can certainly work towards that end in the PEI phase (or in the DXE
phase, using the DXE services) in a specific firmware that aims to
conform to both PI and UEFI. Because, the effects that those low-level
operations will have on the UEFI level (and consequently, on the OS) are
well defined in the PI spec.

> 
>> However, you are right that *just* the UEFI memmap entry is not
>> sufficient, according to the PCI firmware spec. (Regardless of the fact
>> that in practice, just the memmap entry does keep Linux happy. Or is it
>> about to change?)
>>
> 
> The kernel uses the UEFI memory map for two purposes:
> - finding out where memory is, and which parts are usable (i.e., non-reserved)
> - setting up page tables to allow UEFI runtime services calls, which
> may include MMIO mappings
> 
> This means that MMIO regions in the UEFI memory map are *not*
> considered reservations. [...]

Yes, I understand that. Now please understand that my suggestion was
never to cover the MMCONFIG area with MMIO type memory; all along I've
been saying "reserved memory".

(Again, this is now independent of the patch.)

Thanks,
Laszlo

Re: [Qemu-devel] [PATCH v2] hw/arm/virt-acpi - reserve ECAM space as PNP0C02 device

2017-01-16 Thread Ard Biesheuvel 
On 16 January 2017 at 22:35, Laszlo Ersek  wrote:
> On 01/16/17 22:23, Ard Biesheuvel wrote:
>> On 16 January 2017 at 21:13, Laszlo Ersek  wrote:
>>> On 01/16/17 20:31, Ard Biesheuvel wrote:
 On 16 January 2017 at 18:20, Peter Maydell  
 wrote:
> On 16 January 2017 at 17:30, Ard Biesheuvel  
> wrote:
>> On 16 January 2017 at 17:25, Peter Maydell  
>> wrote:
>>> On 13 January 2017 at 17:32, Ard Biesheuvel  
>>> wrote:
 Linux for arm64 v4.10 and later will complain if the ECAM config space 
 is
 not reserved in the ACPI namespace:

   acpi PNP0A08:00: [Firmware Bug]: ECAM area [mem 
 0x3f00-0x3fff] not reserved in ACPI namespace

 The rationale is that OSes that don't consume the MCFG table should 
 still
 be able to infer that the PCI config space MMIO region is occupied.

 So update the ACPI table generation routine to add this reservation.

 Signed-off-by: Ard Biesheuvel 
 ---
  hw/arm/virt-acpi-build.c | 7 +++
  1 file changed, 7 insertions(+)

 diff --git a/hw/arm/virt-acpi-build.c b/hw/arm/virt-acpi-build.c
 index 085a61117378..50d52f685f68 100644
 --- a/hw/arm/virt-acpi-build.c
 +++ b/hw/arm/virt-acpi-build.c
 @@ -310,6 +310,13 @@ static void acpi_dsdt_add_pci(Aml *scope, const 
 MemMapEntry *memmap,
  Aml *dev_rp0 = aml_device("%s", "RP0");
  aml_append(dev_rp0, aml_name_decl("_ADR", aml_int(0)));
  aml_append(dev, dev_rp0);
 +
 +Aml *dev_res0 = aml_device("%s", "RES0");
 +aml_append(dev_res0, aml_name_decl("_HID", 
 aml_string("PNP0C02")));
 +crs = aml_resource_template();
 +aml_append(crs, aml_memory32_fixed(base_ecam, size_ecam, 
 AML_READ_WRITE));
 +aml_append(dev_res0, aml_name_decl("_CRS", crs));
 +aml_append(dev, dev_res0);
  aml_append(scope, dev);
  }
>>>
>>> This needs to be controlled via the machine class back-compat
>>> machinery in hw/arm/virt.c so that it only happens for virt-2.9
>>> and later.
>>>
>>
>> Why exactly?
>
> Because the "virt-2.8" machine has to present to the guest
> exactly what "virt" did as of the QEMU 2.8 release, including
> any bugs or missing things we happened to have in our ACPI
> tables. This allows cross-version compatibility (including
> VM migration). Drew will have a more detailed explanation
> if you need it.
>

 I suspected as much.

 But in this case, I am not sure if it is worth the trouble: the
 generated data is only consumed at boot time by the firmware, and I
 suppose migration involves freezing a VM, including whatever resident
 firmware image was used to boot the OS, and so this is unlikely to
 affect migration.

 But I will let Drew explain ...
>>>
>>> The PCI Firmware Specification (rev 3.1) says in 4.1.2. "MCFG Table
>>> Description": "The resources can *optionally* be returned in [...]
>>> EFIGetMemoryMap as reserved memory [...]". (Emphasis mine.) Linux seems
>>> to *insist* on this kind of reservation however.
>>>
>>
>> No, not at the UEFI level but at the ACPI level. Reservations in the
>> UEFI memory map describe memory not MMIO space
>>
>>> PNP0C02 is "General ID for reserving resources required by PnP
>>> motherboard registers. (Not device specific.)", according to
>>> .
>>> So what this patch does is reserve a memory area through ACPI,
>>> practically as an unspecified "platform resource".
>>>
>>
>> This has been discussed at great length on the linux mailing lists
>>
>> https://patchwork.kernel.org/patch/9453149/
>>
>>> There's an alternative that's contained entirely in the firmware. You
>>> can cover the MMCONFIG area in ArmVirtQemu with an EfiReservedMemoryType
>>> memory map entry (by producing an appropriate memalloc HOB in PEI, or by
>>> calling the appropriate gDS memory space map functions in DXE). OVMF
>>> does the former (memalloc HOB).
>>>
>>> In ArmVirtQemu, we grab the MMCONFIG range from "pci-host-ecam-generic",
>>> from QEMU's DTB. If you don't dislike the idea, we could cover the range
>>> as well, right in "ArmVirtPkg/Library/FdtPciPcdProducerLib". That lib
>>> instance already sets the base address PCD, and makes sure that the
>>> relevant code is executed only once (in whatever driver module the
>>> library instance was built into). You could call the gDS functions
>>> mentioned above from that spot. (The library instance is already
>>> restricted to DXE_DRIVER and UEFI_DRIVER modules.)
>>>
>>
>> In

Re: [Qemu-devel] [PATCH v2] hw/arm/virt-acpi - reserve ECAM space as PNP0C02 device

2017-01-16 Thread Laszlo Ersek 
On 01/16/17 22:23, Ard Biesheuvel wrote:
> On 16 January 2017 at 21:13, Laszlo Ersek  wrote:
>> On 01/16/17 20:31, Ard Biesheuvel wrote:
>>> On 16 January 2017 at 18:20, Peter Maydell  wrote:
 On 16 January 2017 at 17:30, Ard Biesheuvel  
 wrote:
> On 16 January 2017 at 17:25, Peter Maydell  
> wrote:
>> On 13 January 2017 at 17:32, Ard Biesheuvel  
>> wrote:
>>> Linux for arm64 v4.10 and later will complain if the ECAM config space 
>>> is
>>> not reserved in the ACPI namespace:
>>>
>>>   acpi PNP0A08:00: [Firmware Bug]: ECAM area [mem 
>>> 0x3f00-0x3fff] not reserved in ACPI namespace
>>>
>>> The rationale is that OSes that don't consume the MCFG table should 
>>> still
>>> be able to infer that the PCI config space MMIO region is occupied.
>>>
>>> So update the ACPI table generation routine to add this reservation.
>>>
>>> Signed-off-by: Ard Biesheuvel 
>>> ---
>>>  hw/arm/virt-acpi-build.c | 7 +++
>>>  1 file changed, 7 insertions(+)
>>>
>>> diff --git a/hw/arm/virt-acpi-build.c b/hw/arm/virt-acpi-build.c
>>> index 085a61117378..50d52f685f68 100644
>>> --- a/hw/arm/virt-acpi-build.c
>>> +++ b/hw/arm/virt-acpi-build.c
>>> @@ -310,6 +310,13 @@ static void acpi_dsdt_add_pci(Aml *scope, const 
>>> MemMapEntry *memmap,
>>>  Aml *dev_rp0 = aml_device("%s", "RP0");
>>>  aml_append(dev_rp0, aml_name_decl("_ADR", aml_int(0)));
>>>  aml_append(dev, dev_rp0);
>>> +
>>> +Aml *dev_res0 = aml_device("%s", "RES0");
>>> +aml_append(dev_res0, aml_name_decl("_HID", aml_string("PNP0C02")));
>>> +crs = aml_resource_template();
>>> +aml_append(crs, aml_memory32_fixed(base_ecam, size_ecam, 
>>> AML_READ_WRITE));
>>> +aml_append(dev_res0, aml_name_decl("_CRS", crs));
>>> +aml_append(dev, dev_res0);
>>>  aml_append(scope, dev);
>>>  }
>>
>> This needs to be controlled via the machine class back-compat
>> machinery in hw/arm/virt.c so that it only happens for virt-2.9
>> and later.
>>
>
> Why exactly?

 Because the "virt-2.8" machine has to present to the guest
 exactly what "virt" did as of the QEMU 2.8 release, including
 any bugs or missing things we happened to have in our ACPI
 tables. This allows cross-version compatibility (including
 VM migration). Drew will have a more detailed explanation
 if you need it.

>>>
>>> I suspected as much.
>>>
>>> But in this case, I am not sure if it is worth the trouble: the
>>> generated data is only consumed at boot time by the firmware, and I
>>> suppose migration involves freezing a VM, including whatever resident
>>> firmware image was used to boot the OS, and so this is unlikely to
>>> affect migration.
>>>
>>> But I will let Drew explain ...
>>
>> The PCI Firmware Specification (rev 3.1) says in 4.1.2. "MCFG Table
>> Description": "The resources can *optionally* be returned in [...]
>> EFIGetMemoryMap as reserved memory [...]". (Emphasis mine.) Linux seems
>> to *insist* on this kind of reservation however.
>>
> 
> No, not at the UEFI level but at the ACPI level. Reservations in the
> UEFI memory map describe memory not MMIO space
> 
>> PNP0C02 is "General ID for reserving resources required by PnP
>> motherboard registers. (Not device specific.)", according to
>> .
>> So what this patch does is reserve a memory area through ACPI,
>> practically as an unspecified "platform resource".
>>
> 
> This has been discussed at great length on the linux mailing lists
> 
> https://patchwork.kernel.org/patch/9453149/
> 
>> There's an alternative that's contained entirely in the firmware. You
>> can cover the MMCONFIG area in ArmVirtQemu with an EfiReservedMemoryType
>> memory map entry (by producing an appropriate memalloc HOB in PEI, or by
>> calling the appropriate gDS memory space map functions in DXE). OVMF
>> does the former (memalloc HOB).
>>
>> In ArmVirtQemu, we grab the MMCONFIG range from "pci-host-ecam-generic",
>> from QEMU's DTB. If you don't dislike the idea, we could cover the range
>> as well, right in "ArmVirtPkg/Library/FdtPciPcdProducerLib". That lib
>> instance already sets the base address PCD, and makes sure that the
>> relevant code is executed only once (in whatever driver module the
>> library instance was built into). You could call the gDS functions
>> mentioned above from that spot. (The library instance is already
>> restricted to DXE_DRIVER and UEFI_DRIVER modules.)
>>
> 
> In general, I think describing MMIO in the UEFI memory map is not very
> useful, and counter to the spec, which mentions that the memory map
> describes memory ("however it is used"), not memory

Re: [Qemu-devel] [PATCH v2] hw/arm/virt-acpi - reserve ECAM space as PNP0C02 device

2017-01-16 Thread Ard Biesheuvel 
On 16 January 2017 at 21:13, Laszlo Ersek  wrote:
> On 01/16/17 20:31, Ard Biesheuvel wrote:
>> On 16 January 2017 at 18:20, Peter Maydell  wrote:
>>> On 16 January 2017 at 17:30, Ard Biesheuvel  
>>> wrote:
 On 16 January 2017 at 17:25, Peter Maydell  
 wrote:
> On 13 January 2017 at 17:32, Ard Biesheuvel  
> wrote:
>> Linux for arm64 v4.10 and later will complain if the ECAM config space is
>> not reserved in the ACPI namespace:
>>
>>   acpi PNP0A08:00: [Firmware Bug]: ECAM area [mem 0x3f00-0x3fff] 
>> not reserved in ACPI namespace
>>
>> The rationale is that OSes that don't consume the MCFG table should still
>> be able to infer that the PCI config space MMIO region is occupied.
>>
>> So update the ACPI table generation routine to add this reservation.
>>
>> Signed-off-by: Ard Biesheuvel 
>> ---
>>  hw/arm/virt-acpi-build.c | 7 +++
>>  1 file changed, 7 insertions(+)
>>
>> diff --git a/hw/arm/virt-acpi-build.c b/hw/arm/virt-acpi-build.c
>> index 085a61117378..50d52f685f68 100644
>> --- a/hw/arm/virt-acpi-build.c
>> +++ b/hw/arm/virt-acpi-build.c
>> @@ -310,6 +310,13 @@ static void acpi_dsdt_add_pci(Aml *scope, const 
>> MemMapEntry *memmap,
>>  Aml *dev_rp0 = aml_device("%s", "RP0");
>>  aml_append(dev_rp0, aml_name_decl("_ADR", aml_int(0)));
>>  aml_append(dev, dev_rp0);
>> +
>> +Aml *dev_res0 = aml_device("%s", "RES0");
>> +aml_append(dev_res0, aml_name_decl("_HID", aml_string("PNP0C02")));
>> +crs = aml_resource_template();
>> +aml_append(crs, aml_memory32_fixed(base_ecam, size_ecam, 
>> AML_READ_WRITE));
>> +aml_append(dev_res0, aml_name_decl("_CRS", crs));
>> +aml_append(dev, dev_res0);
>>  aml_append(scope, dev);
>>  }
>
> This needs to be controlled via the machine class back-compat
> machinery in hw/arm/virt.c so that it only happens for virt-2.9
> and later.
>

 Why exactly?
>>>
>>> Because the "virt-2.8" machine has to present to the guest
>>> exactly what "virt" did as of the QEMU 2.8 release, including
>>> any bugs or missing things we happened to have in our ACPI
>>> tables. This allows cross-version compatibility (including
>>> VM migration). Drew will have a more detailed explanation
>>> if you need it.
>>>
>>
>> I suspected as much.
>>
>> But in this case, I am not sure if it is worth the trouble: the
>> generated data is only consumed at boot time by the firmware, and I
>> suppose migration involves freezing a VM, including whatever resident
>> firmware image was used to boot the OS, and so this is unlikely to
>> affect migration.
>>
>> But I will let Drew explain ...
>
> The PCI Firmware Specification (rev 3.1) says in 4.1.2. "MCFG Table
> Description": "The resources can *optionally* be returned in [...]
> EFIGetMemoryMap as reserved memory [...]". (Emphasis mine.) Linux seems
> to *insist* on this kind of reservation however.
>

No, not at the UEFI level but at the ACPI level. Reservations in the
UEFI memory map describe memory not MMIO space

> PNP0C02 is "General ID for reserving resources required by PnP
> motherboard registers. (Not device specific.)", according to
> .
> So what this patch does is reserve a memory area through ACPI,
> practically as an unspecified "platform resource".
>

This has been discussed at great length on the linux mailing lists

https://patchwork.kernel.org/patch/9453149/

> There's an alternative that's contained entirely in the firmware. You
> can cover the MMCONFIG area in ArmVirtQemu with an EfiReservedMemoryType
> memory map entry (by producing an appropriate memalloc HOB in PEI, or by
> calling the appropriate gDS memory space map functions in DXE). OVMF
> does the former (memalloc HOB).
>
> In ArmVirtQemu, we grab the MMCONFIG range from "pci-host-ecam-generic",
> from QEMU's DTB. If you don't dislike the idea, we could cover the range
> as well, right in "ArmVirtPkg/Library/FdtPciPcdProducerLib". That lib
> instance already sets the base address PCD, and makes sure that the
> relevant code is executed only once (in whatever driver module the
> library instance was built into). You could call the gDS functions
> mentioned above from that spot. (The library instance is already
> restricted to DXE_DRIVER and UEFI_DRIVER modules.)
>

In general, I think describing MMIO in the UEFI memory map is not very
useful, and counter to the spec, which mentions that the memory map
describes memory ("however it is used"), not memory *space* (unless
UEFI itself needs to access it to implement runtime services)

Re: [Qemu-devel] [PATCH v2] hw/arm/virt-acpi - reserve ECAM space as PNP0C02 device

2017-01-16 Thread Laszlo Ersek 
On 01/16/17 20:31, Ard Biesheuvel wrote:
> On 16 January 2017 at 18:20, Peter Maydell  wrote:
>> On 16 January 2017 at 17:30, Ard Biesheuvel  
>> wrote:
>>> On 16 January 2017 at 17:25, Peter Maydell  wrote:
 On 13 January 2017 at 17:32, Ard Biesheuvel  
 wrote:
> Linux for arm64 v4.10 and later will complain if the ECAM config space is
> not reserved in the ACPI namespace:
>
>   acpi PNP0A08:00: [Firmware Bug]: ECAM area [mem 0x3f00-0x3fff] 
> not reserved in ACPI namespace
>
> The rationale is that OSes that don't consume the MCFG table should still
> be able to infer that the PCI config space MMIO region is occupied.
>
> So update the ACPI table generation routine to add this reservation.
>
> Signed-off-by: Ard Biesheuvel 
> ---
>  hw/arm/virt-acpi-build.c | 7 +++
>  1 file changed, 7 insertions(+)
>
> diff --git a/hw/arm/virt-acpi-build.c b/hw/arm/virt-acpi-build.c
> index 085a61117378..50d52f685f68 100644
> --- a/hw/arm/virt-acpi-build.c
> +++ b/hw/arm/virt-acpi-build.c
> @@ -310,6 +310,13 @@ static void acpi_dsdt_add_pci(Aml *scope, const 
> MemMapEntry *memmap,
>  Aml *dev_rp0 = aml_device("%s", "RP0");
>  aml_append(dev_rp0, aml_name_decl("_ADR", aml_int(0)));
>  aml_append(dev, dev_rp0);
> +
> +Aml *dev_res0 = aml_device("%s", "RES0");
> +aml_append(dev_res0, aml_name_decl("_HID", aml_string("PNP0C02")));
> +crs = aml_resource_template();
> +aml_append(crs, aml_memory32_fixed(base_ecam, size_ecam, 
> AML_READ_WRITE));
> +aml_append(dev_res0, aml_name_decl("_CRS", crs));
> +aml_append(dev, dev_res0);
>  aml_append(scope, dev);
>  }

 This needs to be controlled via the machine class back-compat
 machinery in hw/arm/virt.c so that it only happens for virt-2.9
 and later.

>>>
>>> Why exactly?
>>
>> Because the "virt-2.8" machine has to present to the guest
>> exactly what "virt" did as of the QEMU 2.8 release, including
>> any bugs or missing things we happened to have in our ACPI
>> tables. This allows cross-version compatibility (including
>> VM migration). Drew will have a more detailed explanation
>> if you need it.
>>
> 
> I suspected as much.
> 
> But in this case, I am not sure if it is worth the trouble: the
> generated data is only consumed at boot time by the firmware, and I
> suppose migration involves freezing a VM, including whatever resident
> firmware image was used to boot the OS, and so this is unlikely to
> affect migration.
> 
> But I will let Drew explain ...

The PCI Firmware Specification (rev 3.1) says in 4.1.2. "MCFG Table
Description": "The resources can *optionally* be returned in [...]
EFIGetMemoryMap as reserved memory [...]". (Emphasis mine.) Linux seems
to *insist* on this kind of reservation however.

PNP0C02 is "General ID for reserving resources required by PnP
motherboard registers. (Not device specific.)", according to
.
So what this patch does is reserve a memory area through ACPI,
practically as an unspecified "platform resource".

There's an alternative that's contained entirely in the firmware. You
can cover the MMCONFIG area in ArmVirtQemu with an EfiReservedMemoryType
memory map entry (by producing an appropriate memalloc HOB in PEI, or by
calling the appropriate gDS memory space map functions in DXE). OVMF
does the former (memalloc HOB).

In ArmVirtQemu, we grab the MMCONFIG range from "pci-host-ecam-generic",
from QEMU's DTB. If you don't dislike the idea, we could cover the range
as well, right in "ArmVirtPkg/Library/FdtPciPcdProducerLib". That lib
instance already sets the base address PCD, and makes sure that the
relevant code is executed only once (in whatever driver module the
library instance was built into). You could call the gDS functions
mentioned above from that spot. (The library instance is already
restricted to DXE_DRIVER and UEFI_DRIVER modules.)

Thanks!
Laszlo

Re: [Qemu-devel] [PATCH v2] hw/arm/virt-acpi - reserve ECAM space as PNP0C02 device

2017-01-16 Thread Ard Biesheuvel 
On 16 January 2017 at 18:20, Peter Maydell  wrote:
> On 16 January 2017 at 17:30, Ard Biesheuvel  wrote:
>> On 16 January 2017 at 17:25, Peter Maydell  wrote:
>>> On 13 January 2017 at 17:32, Ard Biesheuvel  
>>> wrote:
 Linux for arm64 v4.10 and later will complain if the ECAM config space is
 not reserved in the ACPI namespace:

   acpi PNP0A08:00: [Firmware Bug]: ECAM area [mem 0x3f00-0x3fff] 
 not reserved in ACPI namespace

 The rationale is that OSes that don't consume the MCFG table should still
 be able to infer that the PCI config space MMIO region is occupied.

 So update the ACPI table generation routine to add this reservation.

 Signed-off-by: Ard Biesheuvel 
 ---
  hw/arm/virt-acpi-build.c | 7 +++
  1 file changed, 7 insertions(+)

 diff --git a/hw/arm/virt-acpi-build.c b/hw/arm/virt-acpi-build.c
 index 085a61117378..50d52f685f68 100644
 --- a/hw/arm/virt-acpi-build.c
 +++ b/hw/arm/virt-acpi-build.c
 @@ -310,6 +310,13 @@ static void acpi_dsdt_add_pci(Aml *scope, const 
 MemMapEntry *memmap,
  Aml *dev_rp0 = aml_device("%s", "RP0");
  aml_append(dev_rp0, aml_name_decl("_ADR", aml_int(0)));
  aml_append(dev, dev_rp0);
 +
 +Aml *dev_res0 = aml_device("%s", "RES0");
 +aml_append(dev_res0, aml_name_decl("_HID", aml_string("PNP0C02")));
 +crs = aml_resource_template();
 +aml_append(crs, aml_memory32_fixed(base_ecam, size_ecam, 
 AML_READ_WRITE));
 +aml_append(dev_res0, aml_name_decl("_CRS", crs));
 +aml_append(dev, dev_res0);
  aml_append(scope, dev);
  }
>>>
>>> This needs to be controlled via the machine class back-compat
>>> machinery in hw/arm/virt.c so that it only happens for virt-2.9
>>> and later.
>>>
>>
>> Why exactly?
>
> Because the "virt-2.8" machine has to present to the guest
> exactly what "virt" did as of the QEMU 2.8 release, including
> any bugs or missing things we happened to have in our ACPI
> tables. This allows cross-version compatibility (including
> VM migration). Drew will have a more detailed explanation
> if you need it.
>

I suspected as much.

But in this case, I am not sure if it is worth the trouble: the
generated data is only consumed at boot time by the firmware, and I
suppose migration involves freezing a VM, including whatever resident
firmware image was used to boot the OS, and so this is unlikely to
affect migration.

But I will let Drew explain ...

Thanks,
Ard.

Re: [Qemu-devel] [PATCH v2] hw/arm/virt-acpi - reserve ECAM space as PNP0C02 device

2017-01-16 Thread Peter Maydell 
On 16 January 2017 at 17:30, Ard Biesheuvel  wrote:
> On 16 January 2017 at 17:25, Peter Maydell  wrote:
>> On 13 January 2017 at 17:32, Ard Biesheuvel  
>> wrote:
>>> Linux for arm64 v4.10 and later will complain if the ECAM config space is
>>> not reserved in the ACPI namespace:
>>>
>>>   acpi PNP0A08:00: [Firmware Bug]: ECAM area [mem 0x3f00-0x3fff] 
>>> not reserved in ACPI namespace
>>>
>>> The rationale is that OSes that don't consume the MCFG table should still
>>> be able to infer that the PCI config space MMIO region is occupied.
>>>
>>> So update the ACPI table generation routine to add this reservation.
>>>
>>> Signed-off-by: Ard Biesheuvel 
>>> ---
>>>  hw/arm/virt-acpi-build.c | 7 +++
>>>  1 file changed, 7 insertions(+)
>>>
>>> diff --git a/hw/arm/virt-acpi-build.c b/hw/arm/virt-acpi-build.c
>>> index 085a61117378..50d52f685f68 100644
>>> --- a/hw/arm/virt-acpi-build.c
>>> +++ b/hw/arm/virt-acpi-build.c
>>> @@ -310,6 +310,13 @@ static void acpi_dsdt_add_pci(Aml *scope, const 
>>> MemMapEntry *memmap,
>>>  Aml *dev_rp0 = aml_device("%s", "RP0");
>>>  aml_append(dev_rp0, aml_name_decl("_ADR", aml_int(0)));
>>>  aml_append(dev, dev_rp0);
>>> +
>>> +Aml *dev_res0 = aml_device("%s", "RES0");
>>> +aml_append(dev_res0, aml_name_decl("_HID", aml_string("PNP0C02")));
>>> +crs = aml_resource_template();
>>> +aml_append(crs, aml_memory32_fixed(base_ecam, size_ecam, 
>>> AML_READ_WRITE));
>>> +aml_append(dev_res0, aml_name_decl("_CRS", crs));
>>> +aml_append(dev, dev_res0);
>>>  aml_append(scope, dev);
>>>  }
>>
>> This needs to be controlled via the machine class back-compat
>> machinery in hw/arm/virt.c so that it only happens for virt-2.9
>> and later.
>>
>
> Why exactly?

Because the "virt-2.8" machine has to present to the guest
exactly what "virt" did as of the QEMU 2.8 release, including
any bugs or missing things we happened to have in our ACPI
tables. This allows cross-version compatibility (including
VM migration). Drew will have a more detailed explanation
if you need it.

thanks
-- PMM

Re: [Qemu-devel] [PATCH v2] hw/arm/virt-acpi - reserve ECAM space as PNP0C02 device

2017-01-16 Thread Ard Biesheuvel 
On 16 January 2017 at 17:25, Peter Maydell  wrote:
> On 13 January 2017 at 17:32, Ard Biesheuvel  wrote:
>> Linux for arm64 v4.10 and later will complain if the ECAM config space is
>> not reserved in the ACPI namespace:
>>
>>   acpi PNP0A08:00: [Firmware Bug]: ECAM area [mem 0x3f00-0x3fff] not 
>> reserved in ACPI namespace
>>
>> The rationale is that OSes that don't consume the MCFG table should still
>> be able to infer that the PCI config space MMIO region is occupied.
>>
>> So update the ACPI table generation routine to add this reservation.
>>
>> Signed-off-by: Ard Biesheuvel 
>> ---
>>  hw/arm/virt-acpi-build.c | 7 +++
>>  1 file changed, 7 insertions(+)
>>
>> diff --git a/hw/arm/virt-acpi-build.c b/hw/arm/virt-acpi-build.c
>> index 085a61117378..50d52f685f68 100644
>> --- a/hw/arm/virt-acpi-build.c
>> +++ b/hw/arm/virt-acpi-build.c
>> @@ -310,6 +310,13 @@ static void acpi_dsdt_add_pci(Aml *scope, const 
>> MemMapEntry *memmap,
>>  Aml *dev_rp0 = aml_device("%s", "RP0");
>>  aml_append(dev_rp0, aml_name_decl("_ADR", aml_int(0)));
>>  aml_append(dev, dev_rp0);
>> +
>> +Aml *dev_res0 = aml_device("%s", "RES0");
>> +aml_append(dev_res0, aml_name_decl("_HID", aml_string("PNP0C02")));
>> +crs = aml_resource_template();
>> +aml_append(crs, aml_memory32_fixed(base_ecam, size_ecam, 
>> AML_READ_WRITE));
>> +aml_append(dev_res0, aml_name_decl("_CRS", crs));
>> +aml_append(dev, dev_res0);
>>  aml_append(scope, dev);
>>  }
>
> This needs to be controlled via the machine class back-compat
> machinery in hw/arm/virt.c so that it only happens for virt-2.9
> and later.
>

Why exactly?

Re: [Qemu-devel] [PATCH v2] hw/arm/virt-acpi - reserve ECAM space as PNP0C02 device

2017-01-16 Thread Peter Maydell 
On 13 January 2017 at 17:32, Ard Biesheuvel  wrote:
> Linux for arm64 v4.10 and later will complain if the ECAM config space is
> not reserved in the ACPI namespace:
>
>   acpi PNP0A08:00: [Firmware Bug]: ECAM area [mem 0x3f00-0x3fff] not 
> reserved in ACPI namespace
>
> The rationale is that OSes that don't consume the MCFG table should still
> be able to infer that the PCI config space MMIO region is occupied.
>
> So update the ACPI table generation routine to add this reservation.
>
> Signed-off-by: Ard Biesheuvel 
> ---
>  hw/arm/virt-acpi-build.c | 7 +++
>  1 file changed, 7 insertions(+)
>
> diff --git a/hw/arm/virt-acpi-build.c b/hw/arm/virt-acpi-build.c
> index 085a61117378..50d52f685f68 100644
> --- a/hw/arm/virt-acpi-build.c
> +++ b/hw/arm/virt-acpi-build.c
> @@ -310,6 +310,13 @@ static void acpi_dsdt_add_pci(Aml *scope, const 
> MemMapEntry *memmap,
>  Aml *dev_rp0 = aml_device("%s", "RP0");
>  aml_append(dev_rp0, aml_name_decl("_ADR", aml_int(0)));
>  aml_append(dev, dev_rp0);
> +
> +Aml *dev_res0 = aml_device("%s", "RES0");
> +aml_append(dev_res0, aml_name_decl("_HID", aml_string("PNP0C02")));
> +crs = aml_resource_template();
> +aml_append(crs, aml_memory32_fixed(base_ecam, size_ecam, 
> AML_READ_WRITE));
> +aml_append(dev_res0, aml_name_decl("_CRS", crs));
> +aml_append(dev, dev_res0);
>  aml_append(scope, dev);
>  }

This needs to be controlled via the machine class back-compat
machinery in hw/arm/virt.c so that it only happens for virt-2.9
and later.

thanks
-- PMM

[Qemu-devel] [PATCH v2] hw/arm/virt-acpi - reserve ECAM space as PNP0C02 device

2017-01-13 Thread Ard Biesheuvel 
Linux for arm64 v4.10 and later will complain if the ECAM config space is
not reserved in the ACPI namespace:

  acpi PNP0A08:00: [Firmware Bug]: ECAM area [mem 0x3f00-0x3fff] not 
reserved in ACPI namespace

The rationale is that OSes that don't consume the MCFG table should still
be able to infer that the PCI config space MMIO region is occupied.

So update the ACPI table generation routine to add this reservation.

Signed-off-by: Ard Biesheuvel 
---
 hw/arm/virt-acpi-build.c | 7 +++
 1 file changed, 7 insertions(+)

diff --git a/hw/arm/virt-acpi-build.c b/hw/arm/virt-acpi-build.c
index 085a61117378..50d52f685f68 100644
--- a/hw/arm/virt-acpi-build.c
+++ b/hw/arm/virt-acpi-build.c
@@ -310,6 +310,13 @@ static void acpi_dsdt_add_pci(Aml *scope, const 
MemMapEntry *memmap,
 Aml *dev_rp0 = aml_device("%s", "RP0");
 aml_append(dev_rp0, aml_name_decl("_ADR", aml_int(0)));
 aml_append(dev, dev_rp0);
+
+Aml *dev_res0 = aml_device("%s", "RES0");
+aml_append(dev_res0, aml_name_decl("_HID", aml_string("PNP0C02")));
+crs = aml_resource_template();
+aml_append(crs, aml_memory32_fixed(base_ecam, size_ecam, AML_READ_WRITE));
+aml_append(dev_res0, aml_name_decl("_CRS", crs));
+aml_append(dev, dev_res0);
 aml_append(scope, dev);
 }
 
-- 
2.7.4