Re: [Xen-devel] [PATCH v2 11/16] ARM64: ACPI: Check if it runs on Xen to enable or disable ACPI

[Shannon Zhao]

On 2016/1/18 23:07, Stefano Stabellini wrote:
> On Mon, 18 Jan 2016, Mark Rutland wrote:
>> > On Fri, Jan 15, 2016 at 02:55:24PM +0800, Shannon Zhao wrote:
>>> > > From: Shannon Zhao 
>>> > > 
>>> > > When it's a Xen domain0 booting with ACPI, it will supply a /chosen and
>>> > > a /hypervisor node in DT. So check if it needs to enable ACPI.
>>> > > 
>>> > > Signed-off-by: Shannon Zhao 
>>> > > ---
>>> > >  arch/arm64/kernel/acpi.c | 12 
>>> > >  1 file changed, 8 insertions(+), 4 deletions(-)
>>> > > 
>>> > > diff --git a/arch/arm64/kernel/acpi.c b/arch/arm64/kernel/acpi.c
>>> > > index d1ce8e2..4e92be0 100644
>>> > > --- a/arch/arm64/kernel/acpi.c
>>> > > +++ b/arch/arm64/kernel/acpi.c
>>> > > @@ -67,10 +67,13 @@ static int __init dt_scan_depth1_nodes(unsigned 
>>> > > long node,
>>> > >  {
>>> > > /*
>>> > >  * Return 1 as soon as we encounter a node at depth 1 that is
>>> > > -* not the /chosen node.
>>> > > +* not the /chosen node, or /hypervisor node when running on 
>>> > > Xen.
>>> > >  */
>>> > > -   if (depth == 1 && (strcmp(uname, "chosen") != 0))
>>> > > -   return 1;
>>> > > +   if (depth == 1 && (strcmp(uname, "chosen") != 0)) {
>>> > > +   if (!xen_initial_domain() || (strcmp(uname, 
>>> > > "hypervisor") != 0))
>>> > > +   return 1;
>>> > > +   }
>>> > > +
>>> > > return 0;
>>> > >  }
>> > 
>> > As this is changing the semantic of an "empty" DT, we should consider
>> > now if there's anything else that might also need to exist in an "empty"
>> > DT. We don't want to change this again in future if we don't have to,
>> > given the compatiblity nightmare that's sure to result.
>> > 
>> > We should also consider if the "hypervisor" node name is sufficient (I
>> > think it is, but let's not assume anything).
>>From Xen point of view I think it is enough: real hardware is described
> in ACPI anyway and anything hypervisor related can be done via
> hypercalls once Xen support is discovered, for which the hypervisor node
> is sufficient.

Yes, I think the hypervisor node is sufficient for current Xen ACPI support.

-- 
Shannon


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Re: [Xen-devel] [PATCH v2 11/16] ARM64: ACPI: Check if it runs on Xen to enable or disable ACPI

[Stefano Stabellini]

On Mon, 18 Jan 2016, Mark Rutland wrote:
> On Fri, Jan 15, 2016 at 02:55:24PM +0800, Shannon Zhao wrote:
> > From: Shannon Zhao 
> > 
> > When it's a Xen domain0 booting with ACPI, it will supply a /chosen and
> > a /hypervisor node in DT. So check if it needs to enable ACPI.
> > 
> > Signed-off-by: Shannon Zhao 
> > ---
> >  arch/arm64/kernel/acpi.c | 12 
> >  1 file changed, 8 insertions(+), 4 deletions(-)
> > 
> > diff --git a/arch/arm64/kernel/acpi.c b/arch/arm64/kernel/acpi.c
> > index d1ce8e2..4e92be0 100644
> > --- a/arch/arm64/kernel/acpi.c
> > +++ b/arch/arm64/kernel/acpi.c
> > @@ -67,10 +67,13 @@ static int __init dt_scan_depth1_nodes(unsigned long 
> > node,
> >  {
> > /*
> >  * Return 1 as soon as we encounter a node at depth 1 that is
> > -* not the /chosen node.
> > +* not the /chosen node, or /hypervisor node when running on Xen.
> >  */
> > -   if (depth == 1 && (strcmp(uname, "chosen") != 0))
> > -   return 1;
> > +   if (depth == 1 && (strcmp(uname, "chosen") != 0)) {
> > +   if (!xen_initial_domain() || (strcmp(uname, "hypervisor") != 0))
> > +   return 1;
> > +   }
> > +
> > return 0;
> >  }
> 
> As this is changing the semantic of an "empty" DT, we should consider
> now if there's anything else that might also need to exist in an "empty"
> DT. We don't want to change this again in future if we don't have to,
> given the compatiblity nightmare that's sure to result.
> 
> We should also consider if the "hypervisor" node name is sufficient (I
> think it is, but let's not assume anything).

>From Xen point of view I think it is enough: real hardware is described
in ACPI anyway and anything hypervisor related can be done via
hypercalls once Xen support is discovered, for which the hypervisor node
is sufficient.

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Re: [Xen-devel] [PATCH v2 11/16] ARM64: ACPI: Check if it runs on Xen to enable or disable ACPI

[Mark Rutland]

On Fri, Jan 15, 2016 at 02:55:24PM +0800, Shannon Zhao wrote:
> From: Shannon Zhao 
> 
> When it's a Xen domain0 booting with ACPI, it will supply a /chosen and
> a /hypervisor node in DT. So check if it needs to enable ACPI.
> 
> Signed-off-by: Shannon Zhao 
> ---
>  arch/arm64/kernel/acpi.c | 12 
>  1 file changed, 8 insertions(+), 4 deletions(-)
> 
> diff --git a/arch/arm64/kernel/acpi.c b/arch/arm64/kernel/acpi.c
> index d1ce8e2..4e92be0 100644
> --- a/arch/arm64/kernel/acpi.c
> +++ b/arch/arm64/kernel/acpi.c
> @@ -67,10 +67,13 @@ static int __init dt_scan_depth1_nodes(unsigned long node,
>  {
>   /*
>* Return 1 as soon as we encounter a node at depth 1 that is
> -  * not the /chosen node.
> +  * not the /chosen node, or /hypervisor node when running on Xen.
>*/
> - if (depth == 1 && (strcmp(uname, "chosen") != 0))
> - return 1;
> + if (depth == 1 && (strcmp(uname, "chosen") != 0)) {
> + if (!xen_initial_domain() || (strcmp(uname, "hypervisor") != 0))
> + return 1;
> + }
> +
>   return 0;
>  }

As this is changing the semantic of an "empty" DT, we should consider
now if there's anything else that might also need to exist in an "empty"
DT. We don't want to change this again in future if we don't have to,
given the compatiblity nightmare that's sure to result.

We should also consider if the "hypervisor" node name is sufficient (I
think it is, but let's not assume anything).

Mark.

>  
> @@ -184,7 +187,8 @@ void __init acpi_boot_table_init(void)
>   /*
>* Enable ACPI instead of device tree unless
>* - ACPI has been disabled explicitly (acpi=off), or
> -  * - the device tree is not empty (it has more than just a /chosen node)
> +  * - the device tree is not empty (it has more than just a /chosen node,
> +  *   and a /hypervisor node when running on Xen)
>*   and ACPI has not been force enabled (acpi=force)
>*/
>   if (param_acpi_off ||
> -- 
> 2.0.4
> 
> 
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[Xen-devel] [PATCH v2 11/16] ARM64: ACPI: Check if it runs on Xen to enable or disable ACPI

[Shannon Zhao]

From: Shannon Zhao 

When it's a Xen domain0 booting with ACPI, it will supply a /chosen and
a /hypervisor node in DT. So check if it needs to enable ACPI.

Signed-off-by: Shannon Zhao 
---
 arch/arm64/kernel/acpi.c | 12 
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/arch/arm64/kernel/acpi.c b/arch/arm64/kernel/acpi.c
index d1ce8e2..4e92be0 100644
--- a/arch/arm64/kernel/acpi.c
+++ b/arch/arm64/kernel/acpi.c
@@ -67,10 +67,13 @@ static int __init dt_scan_depth1_nodes(unsigned long node,
 {
/*
 * Return 1 as soon as we encounter a node at depth 1 that is
-* not the /chosen node.
+* not the /chosen node, or /hypervisor node when running on Xen.
 */
-   if (depth == 1 && (strcmp(uname, "chosen") != 0))
-   return 1;
+   if (depth == 1 && (strcmp(uname, "chosen") != 0)) {
+   if (!xen_initial_domain() || (strcmp(uname, "hypervisor") != 0))
+   return 1;
+   }
+
return 0;
 }
 
@@ -184,7 +187,8 @@ void __init acpi_boot_table_init(void)
/*
 * Enable ACPI instead of device tree unless
 * - ACPI has been disabled explicitly (acpi=off), or
-* - the device tree is not empty (it has more than just a /chosen node)
+* - the device tree is not empty (it has more than just a /chosen node,
+*   and a /hypervisor node when running on Xen)
 *   and ACPI has not been force enabled (acpi=force)
 */
if (param_acpi_off ||
-- 
2.0.4



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