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Subject: Re: [Xen-devel] [PATCH v2 2/3] x86 Test and expose CPUID faulting
 capabilities in /proc/cpuinfo
To: Kyle Huey <me@kylehuey.com>,
        "Robert O'Callahan" <robert@ocallahan.org>
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From: David Vrabel <david.vrabel@citrix.com>
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On 14/09/16 22:01, Kyle Huey wrote:
> Xen advertises the underlying support for CPUID faulting but not does pass
> through writes to the relevant MSR, nor does it virtualize it, so it does
> not actually work. For now mask off the relevant bit on MSR_PLATFORM_INFO.

Could you clarify in the commit message that it is PV guests that are
affected.

> --- a/arch/x86/xen/enlighten.c
> +++ b/arch/x86/xen/enlighten.c
> @@ -1050,6 +1050,9 @@ static u64 xen_read_msr_safe(unsigned int msr, int *err)
>  #endif
>  			val &= ~X2APIC_ENABLE;
>  		break;
> +	case MSR_PLATFORM_INFO:
> +		val &= ~CPUID_FAULTING_SUPPORT;
> +		break;
>  	}
>  	return val;
>  }

Acked-by: David Vrabel <david.vrabel@citrix.com>

David