[PATCH] xen/arm: Don't set the ACTLR SMP bit for 64 bit guests

[PATCH] xen/arm: Don't set the ACTLR SMP bit for 64 bit guests

[Julien Grall]

The ACTLR register is implementation defined. The SMP bit is CA15 and CA7
specific. Also replace ACTLR_CA15_SMP by ACTLR_V7_SMP.

Signed-off-by: Julien Grall <julien.grall@linaro.org>
---
 xen/arch/arm/domain.c |   18 +++++++++++++-----
 1 file changed, 13 insertions(+), 5 deletions(-)

diff --git a/xen/arch/arm/domain.c b/xen/arch/arm/domain.c
index cb0424d..00f2d14 100644
--- a/xen/arch/arm/domain.c
+++ b/xen/arch/arm/domain.c
@@ -470,11 +470,19 @@ int vcpu_initialise(struct vcpu *v)
 
     v->arch.actlr = READ_SYSREG32(ACTLR_EL1);
 
-    /* XXX: Handle other than CA15 cpus */
-    if ( v->domain->max_vcpus > 1 )
-        v->arch.actlr |= ACTLR_CA15_SMP;
-    else
-        v->arch.actlr &= ~ACTLR_CA15_SMP;
+    if ( is_pv32_domain(v->domain) )
+    {
+        /*
+         * ACTLR is implementation defined. For CA7 and CA15, the SMP
+         * is always at the same position.
+         * Enable SMP bit if the domain has more than 1 VCPU
+         * TODO: Handle others CPUs (ie non CA7 and CA15)
+         */
+        if ( v->domain->max_vcpus > 1 )
+            v->arch.actlr |= ACTLR_V7_SMP;
+        else
+            v->arch.actlr &= ~ACTLR_V7_SMP;
+    }
 
     if ( (rc = vcpu_vgic_init(v)) != 0 )
         return rc;
-- 
1.7.10.4

Re: [PATCH] xen/arm: Don't set the ACTLR SMP bit for 64 bit guests

[Ian Campbell]

On Thu, 2013-08-29 at 18:28 +0100, Julien Grall wrote:
> The ACTLR register is implementation defined. The SMP bit is CA15 and CA7
> specific. Also replace ACTLR_CA15_SMP by ACTLR_V7_SMP.
> 
> Signed-off-by: Julien Grall <julien.grall@linaro.org>

I'm afraid this breaks the arm64 build:
        domain.c: In function 'vcpu_initialise':
        domain.c:482:30: error: 'ACTLR_V7_SMP' undeclared (first use in this function)
        domain.c:482:30: note: each undeclared identifier is reported only once for eac
        h function it appears in
        
I'm not sure it is worth putting *that* much effort into a CA15/CA7
kernel as a 32-bit guest on a 64-bit processor, at least not right now.
The interesting use case of this support is really a 32-bit kernel which
is aware that it is running in AArch32 EL1 on a 64-bit processor (i.e.
knows about the 64-bit processors implementation specific stuff)

How about moving this into a proc info hook, or just ifdeffing it for
32-bit?

> ---
>  xen/arch/arm/domain.c |   18 +++++++++++++-----
>  1 file changed, 13 insertions(+), 5 deletions(-)
> 
> diff --git a/xen/arch/arm/domain.c b/xen/arch/arm/domain.c
> index cb0424d..00f2d14 100644
> --- a/xen/arch/arm/domain.c
> +++ b/xen/arch/arm/domain.c
> @@ -470,11 +470,19 @@ int vcpu_initialise(struct vcpu *v)
>  
>      v->arch.actlr = READ_SYSREG32(ACTLR_EL1);
>  
> -    /* XXX: Handle other than CA15 cpus */
> -    if ( v->domain->max_vcpus > 1 )
> -        v->arch.actlr |= ACTLR_CA15_SMP;
> -    else
> -        v->arch.actlr &= ~ACTLR_CA15_SMP;
> +    if ( is_pv32_domain(v->domain) )
> +    {
> +        /*
> +         * ACTLR is implementation defined. For CA7 and CA15, the SMP
> +         * is always at the same position.
> +         * Enable SMP bit if the domain has more than 1 VCPU
> +         * TODO: Handle others CPUs (ie non CA7 and CA15)
> +         */
> +        if ( v->domain->max_vcpus > 1 )
> +            v->arch.actlr |= ACTLR_V7_SMP;
> +        else
> +            v->arch.actlr &= ~ACTLR_V7_SMP;
> +    }
>  
>      if ( (rc = vcpu_vgic_init(v)) != 0 )
>          return rc;

Re: [PATCH] xen/arm: Don't set the ACTLR SMP bit for 64 bit guests

[Julien Grall]

On 09/03/2013 04:56 PM, Ian Campbell wrote:
> On Thu, 2013-08-29 at 18:28 +0100, Julien Grall wrote:
>> The ACTLR register is implementation defined. The SMP bit is CA15 and CA7
>> specific. Also replace ACTLR_CA15_SMP by ACTLR_V7_SMP.
>>
>> Signed-off-by: Julien Grall <julien.grall@linaro.org>
> 
> I'm afraid this breaks the arm64 build:
>         domain.c: In function 'vcpu_initialise':
>         domain.c:482:30: error: 'ACTLR_V7_SMP' undeclared (first use in this function)
>         domain.c:482:30: note: each undeclared identifier is reported only once for eac
>         h function it appears in
>         
> I'm not sure it is worth putting *that* much effort into a CA15/CA7
> kernel as a 32-bit guest on a 64-bit processor, at least not right now.
> The interesting use case of this support is really a 32-bit kernel which
> is aware that it is running in AArch32 EL1 on a 64-bit processor (i.e.
> knows about the 64-bit processors implementation specific stuff)
> 
> How about moving this into a proc info hook, or just ifdeffing it for
> 32-bit?

The first solution sounds better. I will rewrite the patch to add a proc
info hook.

-- 
Julien Grall