Re: [Xen-devel] [PATCH v2 3/6] xen/arm: read ACTLR on the pcpu where the vcpu will run

[Julien Grall <julien.grall@xxxxxxx>]

Hi Stefano,

On 19/02/18 21:58, Stefano Stabellini wrote:
> On big.LITTLE systems not all cores have the same ACTLR. Instead of
> reading ACTLR and setting v->arch.actlr in vcpu_initialise, do it later
> on the same pcpu where the vcpu will run.
>
> This way, assuming that the vcpu has been created with the right pcpu
> affinity, the guest will be able to read the right ACTLR value, matching
> the one of the physical cpu.
>
> Also move processor_vcpu_initialise(v) to continue_new_vcpu as it
> can modify v->arch.actlr.
>
> Signed-off-by: Stefano Stabellini <sstabellini@xxxxxxxxxx>
>
> ---
>
> Changes in v2:
> - move processor_vcpu_initialise to continue_new_vcpu
> - remove inaccurate sentence from commit message
> ---
>   xen/arch/arm/domain.c | 7 +++----
>   1 file changed, 3 insertions(+), 4 deletions(-)
>
> diff --git a/xen/arch/arm/domain.c b/xen/arch/arm/domain.c
> index a010443..fb51415 100644
> --- a/xen/arch/arm/domain.c
> +++ b/xen/arch/arm/domain.c
> @@ -314,6 +314,9 @@ static void schedule_tail(struct vcpu *prev)
>   
>   static void continue_new_vcpu(struct vcpu *prev)
>   {
> +    current->arch.actlr = READ_SYSREG32(ACTLR_EL1);
Hmmm, I just realised that ACTLR_EL1 has been extended to 64-bit for 
AArch64 state in recent spec.
I don't think this necessary to update it in this series so:

Reviewed-by: Julien Grall <julien.grall@xxxxxxx>

Cheers,


> +    processor_vcpu_initialise(current);
> +
>       schedule_tail(prev);
>   
>       if ( is_idle_vcpu(current) )
> @@ -540,12 +543,8 @@ int vcpu_initialise(struct vcpu *v)
>   
>       v->arch.vmpidr = MPIDR_SMP | vcpuid_to_vaffinity(v->vcpu_id);
>   
> -    v->arch.actlr = READ_SYSREG32(ACTLR_EL1);
> -
>       v->arch.hcr_el2 = get_default_hcr_flags();
>   
> -    processor_vcpu_initialise(v);
> -
>       if ( (rc = vcpu_vgic_init(v)) != 0 )
>           goto fail;
>   
Cheers,

--
Julien Grall

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