Re: [PATCH for-4.12 and older] x86/msr: fix handling of MSR_IA32_PERF_{STATUS/CTL} (again)

[Jan Beulich <jbeulich@xxxxxxxx>]

On 04.02.2021 10:36, Jan Beulich wrote:
> X86_VENDOR_* aren't bit masks in the older trees.
> 
> Reported-by: James Dingwall <james@xxxxxxxxxxxxxx>
> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
> 
> --- a/xen/arch/x86/msr.c
> +++ b/xen/arch/x86/msr.c
> @@ -226,7 +226,8 @@ int guest_rdmsr(const struct vcpu *v, ui
>           */
>      case MSR_IA32_PERF_STATUS:
>      case MSR_IA32_PERF_CTL:
> -        if ( !(cp->x86_vendor & (X86_VENDOR_INTEL | X86_VENDOR_CENTAUR)) )
> +        if ( cp->x86_vendor != X86_VENDOR_INTEL &&
> +             cp->x86_vendor != X86_VENDOR_CENTAUR )
>              goto gp_fault;
>  
>          *val = 0;

Darn - this was only half of it. There's a similar construct
in guest_wrmsr() which also wants replacing.

Jan