KVM: selftests: Add framework to query KVM CPUID bits

Add X86_FEATURE_* magic in the style of KVM-Unit-Tests' implementation,
where the CPUID function, index, output register, and output bit position
are embedded in the macro value.  Add kvm_cpu_has() to query KVM's
supported CPUID and use it set_sregs_test, which is the most prolific
user of manual feature querying.

Opportunstically rename calc_cr4_feature_bits() to
calc_supported_cr4_feature_bits() to better capture how the CR4 bits are
chosen.

Link: https://lore.kernel.org/all/[email protected]
Suggested-by: Paolo Bonzini <[email protected]>
Suggested-by: Jim Mattson <[email protected]>
Signed-off-by: Sean Christopherson <[email protected]>
Link: https://lore.kernel.org/r/[email protected]

1 files changed, 22 insertions, 0 deletions

diff --git a/tools/testing/selftests/kvm/lib/x86_64/processor.c b/tools/testing/selftests/kvm/lib/x86_64/processor.c
index 909ac12e5ec5..10038496fff6 100644
--- a/tools/testing/selftests/kvm/lib/x86_64/processor.c
+++ b/tools/testing/selftests/kvm/lib/x86_64/processor.c
@@ -734,6 +734,28 @@ struct kvm_cpuid2 *kvm_get_supported_cpuid(void)
 	return cpuid;
 }
 
+bool kvm_cpuid_has(const struct kvm_cpuid2 *cpuid,
+		   struct kvm_x86_cpu_feature feature)
+{
+	const struct kvm_cpuid_entry2 *entry;
+	int i;
+
+	for (i = 0; i < cpuid->nent; i++) {
+		entry = &cpuid->entries[i];
+
+		/*
+		 * The output registers in kvm_cpuid_entry2 are in alphabetical
+		 * order, but kvm_x86_cpu_feature matches that mess, so yay
+		 * pointer shenanigans!
+		 */
+		if (entry->function == feature.function &&
+		    entry->index == feature.index)
+			return (&entry->eax)[feature.reg] & BIT(feature.bit);
+	}
+
+	return false;
+}
+
 uint64_t kvm_get_feature_msr(uint64_t msr_index)
 {
 	struct {