x86/MCE: restore CPU vendor reporting to the outside world

The records reported used to contain Linux enumerators. We first broke
that connection when purging unused ones, and then again when switching to
the bit mask forms.

Fixes: 4084130511 ("x86/cpu: Drop unused X86_VENDOR_* values")
Fixes: 0cd074144c ("x86/cpu: Renumber X86_VENDOR_* to form a bitmap")
Signed-off-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Jason Andryuk <jason.andryuk@amd.com>
master commit: a94c5fd829
master date: 2026-02-23 08:39:58 +0100

xen/arch/x86/cpu/mcheck/mce.c

@@ -858,6 +858,22 @@ void *x86_mcinfo_reserve(struct mc_info *mi,
     return mic_index;
 }
 
+/* Linux values need using when reporting CPU vendors to the outside. */
+static unsigned int xen2linux_vendor(unsigned int vendor)
+{
+    switch ( vendor )
+    {
+    case X86_VENDOR_INTEL:    return 0;
+    case X86_VENDOR_AMD:      return 2;
+    case X86_VENDOR_CENTAUR:  return 5;
+    case X86_VENDOR_HYGON:    return 9;
+    case X86_VENDOR_SHANGHAI: return 10; /* X86_VENDOR_ZHAOXIN */
+    default: break;
+    }
+
+    return 0xff; /* X86_VENDOR_UNKNOWN */
+}
+
 static void x86_mcinfo_apei_save(
     struct mcinfo_global *mc_global, struct mcinfo_bank *mc_bank)
 {
@@ -866,7 +882,7 @@ 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 = xen2linux_vendor(boot_cpu_data.x86_vendor);
     m.cpuid = cpuid_eax(1);
     m.socketid = mc_global->mc_socketid;
     m.apicid = mc_global->mc_apicid;
@@ -968,7 +984,7 @@ 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 = xen2linux_vendor(c->x86_vendor);
     xcp->mc_model = c->x86_model;
     xcp->mc_step = c->x86_mask;
     xcp->mc_cache_size = c->x86_cache_size;