x86/hvm: Remove cross-vendor checks from MSR handlers.

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

Signed-off-by: Alejandro Vallejo <alejandro.garciavallejo@amd.com>
Reviewed-by: Teddy Astie <teddy.astie@vates.tech>
Acked-by: Jan Beulich <jbeulich@suse.com>

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.vendor & X86_VENDOR_INTEL) )
+        if ( boot_cpu_data.vendor != X86_VENDOR_INTEL )
             goto gp_fault;
+
         rdmsrl(MSR_IA32_PLATFORM_ID, *val);
         break;
 
@@ -189,9 +189,7 @@ int guest_rdmsr(struct vcpu *v, uint32_t msr, uint64_t *val)
          * from Xen's last microcode load, which can be forwarded straight to
          * the guest.
          */
-        if ( !(cp->x86_vendor & (X86_VENDOR_INTEL | X86_VENDOR_AMD)) ||
-             !(boot_cpu_data.vendor &
-               (X86_VENDOR_INTEL | X86_VENDOR_AMD)) ||
+        if ( !(boot_cpu_data.vendor & (X86_VENDOR_INTEL | X86_VENDOR_AMD)) ||
              rdmsr_safe(MSR_AMD_PATCHLEVEL, val) )
             goto gp_fault;
         break;