Re: [Xen-devel] [PATCH] x86/msr: Virtualise MSR_PLATFORM_ID properly

[Jan Beulich <jbeulich@xxxxxxxx>]

On 14.02.2020 20:55, Andrew Cooper wrote:
> --- a/xen/arch/x86/msr.c
> +++ b/xen/arch/x86/msr.c
> @@ -143,6 +143,13 @@ int guest_rdmsr(struct vcpu *v, uint32_t msr, uint64_t 
> *val)
>          /* Not offered to guests. */
>          goto gp_fault;
>  
> +    case MSR_IA32_PLATFORM_ID:
> +        if ( !(cp->x86_vendor & X86_VENDOR_INTEL) ||
> +             !(boot_cpu_data.x86_vendor & X86_VENDOR_INTEL) )

This has turned out to be an unfortunate trap for backporting.
While I understand using & here is the more modern form, could
we perhaps settle on using == / != where possible (i.e. just a
single vendor checked) until 4.12 has gone out of at least
regular support? (The prevailing use with more than one vendor
is with AMD and Hygon, which doesn't go silent as
X86_VENDOR_HYGON doesn't exist yet in 4.12.)

Jan

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