Not a functional change now that cross-vendor guests are not launchable.

Signed-off-by: Alejandro Vallejo <alejandro.garciavallejo@amd.com>
---
 xen/arch/x86/msr.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/xen/arch/x86/msr.c b/xen/arch/x86/msr.c
index ad75a2e108..c9cc4f0692 100644
--- a/xen/arch/x86/msr.c
+++ b/xen/arch/x86/msr.c
@@ -169,9 +169,9 @@ int guest_rdmsr(struct vcpu *v, uint32_t msr, uint64_t *val)
         break;
 
     case MSR_IA32_PLATFORM_ID:
-        if ( !(cp->x86_vendor & X86_VENDOR_INTEL) ||
-             !(boot_cpu_data.x86_vendor & X86_VENDOR_INTEL) )
+        if ( cp->x86_vendor != X86_VENDOR_INTEL )
             goto gp_fault;
+
         rdmsrl(MSR_IA32_PLATFORM_ID, *val);
         break;
 
@@ -190,8 +190,6 @@ int guest_rdmsr(struct vcpu *v, uint32_t msr, uint64_t *val)
          * the guest.
          */
         if ( !(cp->x86_vendor & (X86_VENDOR_INTEL | X86_VENDOR_AMD)) ||
-             !(boot_cpu_data.x86_vendor &
-               (X86_VENDOR_INTEL | X86_VENDOR_AMD)) ||
              rdmsr_safe(MSR_AMD_PATCHLEVEL, val) )
             goto gp_fault;
         break;
-- 
2.43.0

On 22/01/2026 4:49 pm, Alejandro Vallejo wrote:
> Not a functional change now that cross-vendor guests are not launchable.
>
> Signed-off-by: Alejandro Vallejo <alejandro.garciavallejo@amd.com>
> ---
>  xen/arch/x86/msr.c | 6 ++----
>  1 file changed, 2 insertions(+), 4 deletions(-)
>
> diff --git a/xen/arch/x86/msr.c b/xen/arch/x86/msr.c
> index ad75a2e108..c9cc4f0692 100644
> --- a/xen/arch/x86/msr.c
> +++ b/xen/arch/x86/msr.c
> @@ -169,9 +169,9 @@ int guest_rdmsr(struct vcpu *v, uint32_t msr, uint64_t *val)
>          break;
>  
>      case MSR_IA32_PLATFORM_ID:
> -        if ( !(cp->x86_vendor & X86_VENDOR_INTEL) ||
> -             !(boot_cpu_data.x86_vendor & X86_VENDOR_INTEL) )
> +        if ( cp->x86_vendor != X86_VENDOR_INTEL )
>              goto gp_fault;
> +
>          rdmsrl(MSR_IA32_PLATFORM_ID, *val);
>          break;
>  
> @@ -190,8 +190,6 @@ int guest_rdmsr(struct vcpu *v, uint32_t msr, uint64_t *val)
>           * the guest.
>           */
>          if ( !(cp->x86_vendor & (X86_VENDOR_INTEL | X86_VENDOR_AMD)) ||
> -             !(boot_cpu_data.x86_vendor &
> -               (X86_VENDOR_INTEL | X86_VENDOR_AMD)) ||
>               rdmsr_safe(MSR_AMD_PATCHLEVEL, val) )
>              goto gp_fault;
>          break;

Hmm.  Thinking about it, this would probably be cleaner to get rid of
the cp->x86_vendor field entirely, and retain the boot_cpu_data side.

Additionally, this would fix a minor problem I'm having cleaning up the
CPUID code for XSAVE fixes, and provide better cache locality.

~Andrew

Le 22/01/2026 à 17:51, Alejandro Vallejo a écrit :
> Not a functional change now that cross-vendor guests are not launchable.
> 
> Signed-off-by: Alejandro Vallejo <alejandro.garciavallejo@amd.com>
> ---
>   xen/arch/x86/msr.c | 6 ++----
>   1 file changed, 2 insertions(+), 4 deletions(-)
> 
> diff --git a/xen/arch/x86/msr.c b/xen/arch/x86/msr.c
> index ad75a2e108..c9cc4f0692 100644
> --- a/xen/arch/x86/msr.c
> +++ b/xen/arch/x86/msr.c
> @@ -169,9 +169,9 @@ int guest_rdmsr(struct vcpu *v, uint32_t msr, uint64_t *val)
>           break;
>   
>       case MSR_IA32_PLATFORM_ID:
> -        if ( !(cp->x86_vendor & X86_VENDOR_INTEL) ||
> -             !(boot_cpu_data.x86_vendor & X86_VENDOR_INTEL) )
> +        if ( cp->x86_vendor != X86_VENDOR_INTEL )
>               goto gp_fault;
> +
>           rdmsrl(MSR_IA32_PLATFORM_ID, *val);
>           break;
>   
> @@ -190,8 +190,6 @@ int guest_rdmsr(struct vcpu *v, uint32_t msr, uint64_t *val)
>            * the guest.
>            */
>           if ( !(cp->x86_vendor & (X86_VENDOR_INTEL | X86_VENDOR_AMD)) ||
> -             !(boot_cpu_data.x86_vendor &
> -               (X86_VENDOR_INTEL | X86_VENDOR_AMD)) ||
>                rdmsr_safe(MSR_AMD_PATCHLEVEL, val) )
>               goto gp_fault;
>           break;

Reviewed-by: Teddy Astie <teddy.astie@vates.tech>


--
Teddy Astie | Vates XCP-ng Developer

XCP-ng & Xen Orchestra - Vates solutions

web: https://vates.tech