[PATCH 4/5] KVM: selftests: Introduce utilities for checking x86 features

[Ricardo Koller <ricarkol@google.com>]

Add utilities for checking CPU features using the same x86 features
format used in the kernel (defined in cpufeatures.h). This format embeds
the function, index, and register to use. By using this format and these
utilities, tests will not have to define their own feature macros and
will be able to use kvm_cpuid_has(FEATURE_XYZ) or
this_cpu_has(FEATURE_XYZ) without having to worry about what register or
index to use.

Signed-off-by: Ricardo Koller <ricarkol@google.com>
---
 .../selftests/kvm/include/x86_64/cpuid.h      | 61 +++++++++++++++++++
 1 file changed, 61 insertions(+)
 create mode 100644 tools/testing/selftests/kvm/include/x86_64/cpuid.h

diff --git a/tools/testing/selftests/kvm/include/x86_64/cpuid.h b/tools/testing/selftests/kvm/include/x86_64/cpuid.h
new file mode 100644
index 000000000000..4d8c67d528f4
--- /dev/null
+++ b/tools/testing/selftests/kvm/include/x86_64/cpuid.h
@@ -0,0 +1,61 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Adapted from /arch/x86/kvm/cpuid.h
+ */
+
+#ifndef SELFTEST_KVM_CPUID_FEATURE_H
+#define SELFTEST_KVM_CPUID_FEATURE_H
+
+#include <stdint.h>
+#include <asm/cpufeatures.h>
+#include <asm/kvm_para.h>
+#include "reverse_cpuid.h"
+
+static __always_inline u32 *kvm_cpuid_get_register(unsigned int x86_feature)
+{
+	struct kvm_cpuid_entry2 *entry;
+	const struct cpuid_reg cpuid = x86_feature_cpuid(x86_feature);
+
+	entry = kvm_get_supported_cpuid_index(cpuid.function, cpuid.index);
+	if (!entry)
+		return NULL;
+
+	return __cpuid_entry_get_reg(entry, cpuid.reg);
+}
+
+static __always_inline bool kvm_cpuid_has(unsigned int x86_feature)
+{
+	u32 *reg;
+
+	reg = kvm_cpuid_get_register(x86_feature);
+	if (!reg)
+		return false;
+
+	return *reg & __feature_bit(x86_feature);
+}
+
+static __always_inline bool kvm_pv_has(unsigned int kvm_feature)
+{
+	u32 reg;
+
+	reg = kvm_get_supported_cpuid_entry(KVM_CPUID_FEATURES)->eax;
+	return reg & __feature_bit(kvm_feature);
+}
+
+static __always_inline bool this_cpu_has(unsigned int x86_feature)
+{
+	struct kvm_cpuid_entry2 entry;
+	const struct cpuid_reg cpuid = x86_feature_cpuid(x86_feature);
+	u32 *reg;
+
+	entry.eax = cpuid.function;
+	entry.ecx = cpuid.index;
+	__asm__ __volatile__("cpuid"
+			     : "+a"(entry.eax), "=b"(entry.ebx),
+			       "+c"(entry.ecx), "=d"(entry.edx));
+
+	reg = __cpuid_entry_get_reg(&entry, cpuid.reg);
+	return *reg &  __feature_bit(x86_feature);
+}
+
+#endif /* SELFTEST_KVM_CPUID_FEATURE_H */
-- 
2.31.1.368.gbe11c130af-goog