Re: [PATCH] x86/viridian: EOI MSR should always happen in affected vCPU context

[Paul Durrant <xadimgnik@xxxxxxxxx>]

On 01/04/2021 11:22, Roger Pau Monne wrote:
> The HV_X64_MSR_EOI wrmsr should always happen with the target vCPU
> as current, as there's no support for EOI'ing interrupts on a remote
> vCPU.
>
> While there also turn the unconditional assert at the top of the
> function into an error on non-debug builds.
>
> No functional change intended.
>
> Requested-by: Jan Beulich <jbeulich@xxxxxxxx>
> Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
Reviewed-by: Paul Durrant <paul@xxxxxxx>

> ---
>   xen/arch/x86/hvm/viridian/synic.c | 11 ++++++++++-
>   1 file changed, 10 insertions(+), 1 deletion(-)
>
> diff --git a/xen/arch/x86/hvm/viridian/synic.c 
> b/xen/arch/x86/hvm/viridian/synic.c
> index 22e2df27e5d..e18538c60a6 100644
> --- a/xen/arch/x86/hvm/viridian/synic.c
> +++ b/xen/arch/x86/hvm/viridian/synic.c
> @@ -79,11 +79,20 @@ int viridian_synic_wrmsr(struct vcpu *v, uint32_t idx, 
> uint64_t val)
>       struct viridian_vcpu *vv = v->arch.hvm.viridian;
>       struct domain *d = v->domain;
>   
> -    ASSERT(v == current || !v->is_running);
> +    if ( v != current && v->is_running )
> +    {
> +        ASSERT_UNREACHABLE();
> +        return X86EMUL_EXCEPTION;
> +    }
>   
>       switch ( idx )
>       {
>       case HV_X64_MSR_EOI:
> +        if ( v != current )
> +        {
> +            ASSERT_UNREACHABLE();
> +            return X86EMUL_EXCEPTION;
> +        }
>           vlapic_EOI_set(vcpu_vlapic(v));
>           break;
>