[PATCH] x86/CPUID: correct error indicator for max extended leaf

[Jan Beulich <jbeulich@xxxxxxxx>]

With the max base leaf using 0, this one should be using the extended
leaf counterpart thereof, rather than some arbitrary extended leaf.

Fixes: 588a966a572e ("libx86: Introduce x86_cpu_policies_are_compatible()")
Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>

--- a/tools/tests/cpu-policy/test-cpu-policy.c
+++ b/tools/tests/cpu-policy/test-cpu-policy.c
@@ -570,7 +570,7 @@ static void test_is_compatible_failure(v
         {
             .name = "Host extd.max_leaf out of range",
             .guest_cpuid.extd.max_leaf = 1,
-            .e = { 0x80000008, -1, -1 },
+            .e = { 0x80000000, -1, -1 },
         },
         {
             .name = "Host no CPUID faulting, Guest wanted",
--- a/xen/lib/x86/policy.c
+++ b/xen/lib/x86/policy.c
@@ -19,7 +19,7 @@ int x86_cpu_policies_are_compatible(cons
         FAIL_CPUID(0, NA);
 
     if ( guest->cpuid->extd.max_leaf > host->cpuid->extd.max_leaf )
-        FAIL_CPUID(0x80000008, NA);
+        FAIL_CPUID(0x80000000, NA);
 
     /* TODO: Audit more CPUID data. */