[PATCH 38/42] KVM: selftests: Check KVM's supported CPUID, not host CPUID, for XFD

From: Sean Christopherson
Date: Fri Jun 03 2022 - 21:24:49 EST


Use kvm_cpu_has() to check for XFD supported in vm_xsave_req_perm(),
simply checking host CPUID doesn't guarantee KVM supports AMX/XFD.

Opportunistically hoist the check above the bit check; if XFD isn't
supported, it's far better to get a "not supported at all" message, as
opposed to a "feature X isn't supported" message".

Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
---
.../selftests/kvm/include/x86_64/processor.h | 1 +
.../selftests/kvm/lib/x86_64/processor.c | 19 ++-----------------
2 files changed, 3 insertions(+), 17 deletions(-)

diff --git a/tools/testing/selftests/kvm/include/x86_64/processor.h b/tools/testing/selftests/kvm/include/x86_64/processor.h
index 473501e5776e..e97b7c4ce367 100644
--- a/tools/testing/selftests/kvm/include/x86_64/processor.h
+++ b/tools/testing/selftests/kvm/include/x86_64/processor.h
@@ -115,6 +115,7 @@ struct kvm_x86_cpu_feature {
#define X86_FEATURE_XTILECFG KVM_X86_CPU_FEATURE(0xD, 0, EAX, 17)
#define X86_FEATURE_XTILEDATA KVM_X86_CPU_FEATURE(0xD, 0, EAX, 18)
#define X86_FEATURE_XSAVES KVM_X86_CPU_FEATURE(0xD, 1, EAX, 3)
+#define X86_FEATURE_XFD KVM_X86_CPU_FEATURE(0xD, 1, EAX, 4)

/*
* Extended Leafs, a.k.a. AMD defined
diff --git a/tools/testing/selftests/kvm/lib/x86_64/processor.c b/tools/testing/selftests/kvm/lib/x86_64/processor.c
index 0f36f8ac7e9d..f1290540210d 100644
--- a/tools/testing/selftests/kvm/lib/x86_64/processor.c
+++ b/tools/testing/selftests/kvm/lib/x86_64/processor.c
@@ -579,21 +579,6 @@ static void vcpu_setup(struct kvm_vm *vm, struct kvm_vcpu *vcpu)
vcpu_sregs_set(vcpu, &sregs);
}

-#define CPUID_XFD_BIT (1 << 4)
-static bool is_xfd_supported(void)
-{
- int eax, ebx, ecx, edx;
- const int leaf = 0xd, subleaf = 0x1;
-
- __asm__ __volatile__(
- "cpuid"
- : /* output */ "=a"(eax), "=b"(ebx),
- "=c"(ecx), "=d"(edx)
- : /* input */ "0"(leaf), "2"(subleaf));
-
- return !!(eax & CPUID_XFD_BIT);
-}
-
void vm_xsave_req_perm(int bit)
{
int kvm_fd;
@@ -605,6 +590,8 @@ void vm_xsave_req_perm(int bit)
.addr = (unsigned long) &bitmask
};

+ TEST_REQUIRE(kvm_cpu_has(X86_FEATURE_XFD));
+
kvm_fd = open_kvm_dev_path_or_exit();
rc = __kvm_ioctl(kvm_fd, KVM_GET_DEVICE_ATTR, &attr);
close(kvm_fd);
@@ -615,8 +602,6 @@ void vm_xsave_req_perm(int bit)

TEST_REQUIRE(bitmask & (1ULL << bit));

- TEST_REQUIRE(is_xfd_supported());
-
rc = syscall(SYS_arch_prctl, ARCH_REQ_XCOMP_GUEST_PERM, bit);

/*
--
2.36.1.255.ge46751e96f-goog