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

["Kang, Luwei" <luwei.kang@xxxxxxxxx>]

Thank  you Andrew Cooper, this patch indeed resolve my issue and  two point 
need modify.

The code need  move ahead of "break;"
@@ -1101,6 +1101,9 @@ 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);
             break;
+
+            a &= (uint32_t)pv_xfeature_mask;
+            d &= (uint32_t)(pv_xfeature_mask >> 32);
         }

extraneous space after "&".
-    sanitise_featureset(hvm_featureset);
+    sanitise_featureset(hvm_featureset, & hvm_xfeature_mask);


-----Original Message-----
From: Andrew Cooper [mailto:andrew.cooper3@xxxxxxxxxx] 
Sent: Wednesday, June 1, 2016 5:04 PM
To: Kang, Luwei <luwei.kang@xxxxxxxxx>; xen-devel@xxxxxxxxxxxxx
Cc: jbeulich@xxxxxxxx; Han, Huaitong <huaitong.han@xxxxxxxxx>; Wang, Yong Y 
<yong.y.wang@xxxxxxxxx>
Subject: Re: [PATCH] x86/cpuid: fix dom0 crash on skylake machine

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

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