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

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

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@xxxxxxxxxx>

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;



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