Re: [Xen-devel] [PATCH] x86/cpuid: fix dom0 crash on skylake machine

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 01/06/16 05:58, Luwei Kang wrote:
> CPUID.0XD.0X0.EAX is from machine value for dom0, and dom0 kernel will xsetbv
> with xfeatures_mask that is from CPUID.0XD.0X0.EAX, but handle_xsetbv has
> ingored XSTATE_PKRU with hardware protection fault emulation, so dom0 kernel
> will crash on skylake machine with PKRU support.
>
> Signed-off-by: Luwei Kang <luwei.kang@xxxxxxxxx>
> ---
>  xen/arch/x86/traps.c | 3 +++
>  1 file changed, 3 insertions(+)
>
> diff --git a/xen/arch/x86/traps.c b/xen/arch/x86/traps.c
> index 1ef8401..5e72e44 100644
> --- a/xen/arch/x86/traps.c
> +++ b/xen/arch/x86/traps.c
> @@ -1100,6 +1100,9 @@ void pv_cpuid(struct cpu_user_regs *regs)
>               */
>              if ( !is_control_domain(currd) && !is_hardware_domain(currd) )
>                  cpuid_count(leaf, subleaf, &tmp, &b, &tmp, &tmp);
> +
> +            /* PV is not supported by XSTATE_PKRU. */
> +            a &= ~XSTATE_PKRU;
>              break;
>          }
>  

While this does work, it undoes some of the work I started with my cpuid
improvements in 4.7

Does the attached patch also resolve your issue?

~Andrew

Attachment: 0001-xen-x86-Clip-guests-view-of-xfeature_mask-at-the-per.patch
Description: Text Data

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