[PATCH for-4.7] xen/hvm: Fix advertisment of available xstates following c/s c52319642

[PATCH for-4.7] xen/hvm: Fix advertisment of available xstates following c/s c52319642

[Andrew Cooper]

PKU lives in CPUID.7[0].ECX, not EBX.  This causes hardware with BMI1 to
accidentally advertise PKU in CPUID.0xD[0].EAX.  Any OS which proceeds to
blindly write this into %xcr0 takes a #GP fault.  (Experimentally, Windows
Vista 32bit falls into this category.)

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
---
CC: Jan Beulich <JBeulich@suse.com>
CC: Wei Liu <wei.liu2@citrix.com>

This is all going to be far less error prone when I have guest_has_$FEATURE(v)
helpers which read the bits out of a flat array...
---
 xen/arch/x86/hvm/hvm.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c
index e664b34..78db903 100644
--- a/xen/arch/x86/hvm/hvm.c
+++ b/xen/arch/x86/hvm/hvm.c
@@ -3466,7 +3466,7 @@ void hvm_cpuid(unsigned int input, unsigned int *eax, unsigned int *ebx,
                                   xstate_sizes[_XSTATE_BNDCSR]);
             }
 
-            if ( _ebx & cpufeat_mask(X86_FEATURE_PKU) )
+            if ( _ecx & cpufeat_mask(X86_FEATURE_PKU) )
             {
                 xfeature_mask |= XSTATE_PKRU;
                 xstate_size = max(xstate_size,
-- 
2.1.4


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Re: [PATCH for-4.7] xen/hvm: Fix advertisment of available xstates following c/s c52319642

[Wei Liu]

On Fri, Jun 10, 2016 at 07:17:43PM +0100, Andrew Cooper wrote:
> PKU lives in CPUID.7[0].ECX, not EBX.  This causes hardware with BMI1 to
> accidentally advertise PKU in CPUID.0xD[0].EAX.  Any OS which proceeds to
> blindly write this into %xcr0 takes a #GP fault.  (Experimentally, Windows
> Vista 32bit falls into this category.)
> 
> Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
> ---
> CC: Jan Beulich <JBeulich@suse.com>
> CC: Wei Liu <wei.liu2@citrix.com>
> 

Reviewed-by: Wei Liu <wei.liu2@citrix.com>

and

Release-acked-by: Wei Liu <wei.liu2@citrix.com>

> This is all going to be far less error prone when I have guest_has_$FEATURE(v)
> helpers which read the bits out of a flat array...
> ---
>  xen/arch/x86/hvm/hvm.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c
> index e664b34..78db903 100644
> --- a/xen/arch/x86/hvm/hvm.c
> +++ b/xen/arch/x86/hvm/hvm.c
> @@ -3466,7 +3466,7 @@ void hvm_cpuid(unsigned int input, unsigned int *eax, unsigned int *ebx,
>                                    xstate_sizes[_XSTATE_BNDCSR]);
>              }
>  
> -            if ( _ebx & cpufeat_mask(X86_FEATURE_PKU) )
> +            if ( _ecx & cpufeat_mask(X86_FEATURE_PKU) )
>              {
>                  xfeature_mask |= XSTATE_PKRU;
>                  xstate_size = max(xstate_size,
> -- 
> 2.1.4
> 

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Re: [PATCH for-4.7] xen/hvm: Fix advertisment of available xstates following c/s c52319642

[Jan Beulich]

>>> On 10.06.16 at 20:17, <andrew.cooper3@citrix.com> wrote:
> PKU lives in CPUID.7[0].ECX, not EBX.  This causes hardware with BMI1 to
> accidentally advertise PKU in CPUID.0xD[0].EAX.  Any OS which proceeds to
> blindly write this into %xcr0 takes a #GP fault.  (Experimentally, Windows
> Vista 32bit falls into this category.)
> 
> Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>

Reviewed-by: Jan Beulich <jbeulich@suse.com>


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Re: [PATCH for-4.7] xen/hvm: Fix advertisment of available xstates following c/s c52319642

[Wei Liu]

On Mon, Jun 13, 2016 at 03:48:45AM -0600, Jan Beulich wrote:
> >>> On 10.06.16 at 20:17, <andrew.cooper3@citrix.com> wrote:
> > PKU lives in CPUID.7[0].ECX, not EBX.  This causes hardware with BMI1 to
> > accidentally advertise PKU in CPUID.0xD[0].EAX.  Any OS which proceeds to
> > blindly write this into %xcr0 takes a #GP fault.  (Experimentally, Windows
> > Vista 32bit falls into this category.)
> > 
> > Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
> 
> Reviewed-by: Jan Beulich <jbeulich@suse.com>
> 

Pushed to staging and staging-4.7.

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