[PATCH] selftests: kvm/x86: Check if cpuid_d_0_ebx follows XCR0 value change

[Like Xu]

From: Like Xu <likexu@xxxxxxxxxxx>

Intel SDM says the CPUID.0xd.EBX reports the maximum size required by
enabled features in XCR0. Add a simple test that writes two different
non #GP values via  __xsetbv() and verify that the cpuid data is updated.

Opportunistically, move the __x{s,g}etbv helpers  to the x86_64/processor.h

Signed-off-by: Like Xu <likexu@xxxxxxxxxxx>
---
Related link: https://lore.kernel.org/kvm/20220119070427.33801-1-likexu@xxxxxxxxxxx/

 .../selftests/kvm/include/x86_64/processor.h  | 18 ++++++++++
 tools/testing/selftests/kvm/x86_64/amx_test.c | 18 ----------
 .../testing/selftests/kvm/x86_64/cpuid_test.c | 34 +++++++++++++++++--
 3 files changed, 49 insertions(+), 21 deletions(-)

diff --git a/tools/testing/selftests/kvm/include/x86_64/processor.h b/tools/testing/selftests/kvm/include/x86_64/processor.h
index 122447827954..65097ca6d7b2 100644
--- a/tools/testing/selftests/kvm/include/x86_64/processor.h
+++ b/tools/testing/selftests/kvm/include/x86_64/processor.h
@@ -296,6 +296,24 @@ static inline void cpuid(uint32_t *eax, uint32_t *ebx,
 	    : "memory");
 }
 
+static inline u64 __xgetbv(u32 index)
+{
+	u32 eax, edx;
+
+	asm volatile("xgetbv;"
+		     : "=a" (eax), "=d" (edx)
+		     : "c" (index));
+	return eax + ((u64)edx << 32);
+}
+
+static inline void __xsetbv(u32 index, u64 value)
+{
+	u32 eax = value;
+	u32 edx = value >> 32;
+
+	asm volatile("xsetbv" :: "a" (eax), "d" (edx), "c" (index));
+}
+
 #define SET_XMM(__var, __xmm) \
 	asm volatile("movq %0, %%"#__xmm : : "r"(__var) : #__xmm)
 
diff --git a/tools/testing/selftests/kvm/x86_64/amx_test.c b/tools/testing/selftests/kvm/x86_64/amx_test.c
index 523c1e99ed64..c3cbb2dc450d 100644
--- a/tools/testing/selftests/kvm/x86_64/amx_test.c
+++ b/tools/testing/selftests/kvm/x86_64/amx_test.c
@@ -78,24 +78,6 @@ struct xtile_info {
 
 static struct xtile_info xtile;
 
-static inline u64 __xgetbv(u32 index)
-{
-	u32 eax, edx;
-
-	asm volatile("xgetbv;"
-		     : "=a" (eax), "=d" (edx)
-		     : "c" (index));
-	return eax + ((u64)edx << 32);
-}
-
-static inline void __xsetbv(u32 index, u64 value)
-{
-	u32 eax = value;
-	u32 edx = value >> 32;
-
-	asm volatile("xsetbv" :: "a" (eax), "d" (edx), "c" (index));
-}
-
 static inline void __ldtilecfg(void *cfg)
 {
 	asm volatile(".byte 0xc4,0xe2,0x78,0x49,0x00"
diff --git a/tools/testing/selftests/kvm/x86_64/cpuid_test.c b/tools/testing/selftests/kvm/x86_64/cpuid_test.c
index 16d2465c5634..169ec54a928c 100644
--- a/tools/testing/selftests/kvm/x86_64/cpuid_test.c
+++ b/tools/testing/selftests/kvm/x86_64/cpuid_test.c
@@ -20,8 +20,7 @@ struct {
 	u32 index;
 } mangled_cpuids[] = {
 	/*
-	 * These entries depend on the vCPU's XCR0 register and IA32_XSS MSR,
-	 * which are not controlled for by this test.
+	 * These entries depend on the vCPU's XCR0 register and IA32_XSS MSR.
 	 */
 	{.function = 0xd, .index = 0},
 	{.function = 0xd, .index = 1},
@@ -55,6 +54,31 @@ static void test_cpuid_40000000(struct kvm_cpuid2 *guest_cpuid)
 	GUEST_ASSERT(eax == 0x40000001);
 }
 
+static void test_cpuid_d(struct kvm_cpuid2 *guest_cpuid)
+{
+	uint64_t cr4;
+	u32 eax, ebx, ecx, edx;
+	u32 before, after;
+
+	cr4 = get_cr4();
+	cr4 |= X86_CR4_OSXSAVE;
+	set_cr4(cr4);
+
+	__xsetbv(0x0, 0x1);
+	eax = 0xd;
+	ebx = ecx = edx = 0;
+	cpuid(&eax, &ebx, &ecx, &edx);
+	before = ebx;
+
+	__xsetbv(0x0, 0x3);
+	eax = 0xd;
+	ebx = ecx = edx = 0;
+	cpuid(&eax, &ebx, &ecx, &edx);
+	after = ebx;
+
+	GUEST_ASSERT(before != after);
+}
+
 static void guest_main(struct kvm_cpuid2 *guest_cpuid)
 {
 	GUEST_SYNC(1);
@@ -65,6 +89,10 @@ static void guest_main(struct kvm_cpuid2 *guest_cpuid)
 
 	test_cpuid_40000000(guest_cpuid);
 
+	GUEST_SYNC(3);
+
+	test_cpuid_d(guest_cpuid);
+
 	GUEST_DONE();
 }
 
@@ -200,7 +228,7 @@ int main(void)
 
 	vcpu_args_set(vm, VCPU_ID, 1, cpuid_gva);
 
-	for (stage = 0; stage < 3; stage++)
+	for (stage = 0; stage < 4; stage++)
 		run_vcpu(vm, VCPU_ID, stage);
 
 	set_cpuid_after_run(vm, cpuid2);
-- 
2.33.1