Re: [PATCH 10/12] x86/mcheck: Migrate vendor checks to use cpu_vendor()

[Jan Beulich <jbeulich@xxxxxxxx>]

On 06.02.2026 17:15, Alejandro Vallejo wrote:
> @@ -862,7 +861,7 @@ static void x86_mcinfo_apei_save(
>      memset(&m, 0, sizeof(struct mce));
>  
>      m.cpu = mc_global->mc_coreid;
> -    m.cpuvendor = boot_cpu_data.x86_vendor;
> +    m.cpuvendor = cpu_vendor();
>      m.cpuid = cpuid_eax(1);
>      m.socketid = mc_global->mc_socketid;
>      m.apicid = mc_global->mc_apicid;
> @@ -964,7 +963,7 @@ static void cf_check __maybe_unused 
> do_mc_get_cpu_info(void *v)
>                          &xcp->mc_ncores_active, &xcp->mc_nthreads);
>      xcp->mc_cpuid_level = c->cpuid_level;
>      xcp->mc_family = c->x86;
> -    xcp->mc_vendor = c->x86_vendor;
> +    xcp->mc_vendor = cpu_vendor();
>      xcp->mc_model = c->x86_model;
>      xcp->mc_step = c->x86_mask;
>      xcp->mc_cache_size = c->x86_cache_size;

What we do internally is one thing. But what we report to the outside shouldn't
be inaccurate, imo.

> @@ -1122,7 +1121,7 @@ static bool __maybe_unused 
> x86_mc_msrinject_verify(struct xen_mc_msrinject *mci)
>  
>          if ( IS_MCA_BANKREG(reg, mci->mcinj_cpunr) )
>          {
> -            if ( c->x86_vendor == X86_VENDOR_AMD )
> +            if ( (cpu_vendor() & X86_VENDOR_AMD) )

Nit: No need for the extra parentheses here.

> --- a/xen/arch/x86/cpu/mcheck/mce_amd.c
> +++ b/xen/arch/x86/cpu/mcheck/mce_amd.c
> @@ -160,7 +160,7 @@ mcequirk_lookup_amd_quirkdata(const struct cpuinfo_x86 *c)
>  {
>      unsigned int i;
>  
> -    BUG_ON(c->x86_vendor != X86_VENDOR_AMD);
> +    BUG_ON(!(cpu_vendor() & X86_VENDOR_AMD));
>  
>      for ( i = 0; i < ARRAY_SIZE(mce_amd_quirks); i++ )
>      {
> @@ -291,7 +291,7 @@ amd_mcheck_init(const struct cpuinfo_x86 *c, bool bsp)
>      uint32_t i;
>      enum mcequirk_amd_flags quirkflag = 0;
>  
> -    if ( c->x86_vendor != X86_VENDOR_HYGON )
> +    if ( !(cpu_vendor() & X86_VENDOR_HYGON) )
>          quirkflag = mcequirk_lookup_amd_quirkdata(c);

I wonder if this wasn't better switched to the positive for (checking for AMD).
This would the render the BUG_ON() above useless.

> --- a/xen/arch/x86/cpu/mcheck/mce_intel.c
> +++ b/xen/arch/x86/cpu/mcheck/mce_intel.c
> @@ -711,8 +711,8 @@ static bool mce_is_broadcast(struct cpuinfo_x86 *c)
>       * DisplayFamily_DisplayModel encoding of 06H_EH and above,
>       * a MCA signal is broadcast to all logical processors in the system
>       */
> -    if ( c->x86_vendor == X86_VENDOR_INTEL && c->x86 == 6 &&
> -         c->x86_model >= 0xe )
> +    if ( (cpu_vendor() & X86_VENDOR_INTEL) &&
> +         c->x86 == 6 && c->x86_model >= 0xe )

Nit: Why the re-wrapping of lines?

Jan