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

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Message-Id: <20220604012058.1972195-39-seanjc@google.com>
Date:   Sat,  4 Jun 2022 01:20:54 +0000
From:   Sean Christopherson <seanjc@...gle.com>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     kvm@...r.kernel.org, Vitaly Kuznetsov <vkuznets@...hat.com>,
        David Matlack <dmatlack@...gle.com>,
        Jim Mattson <jmattson@...gle.com>, linux-kernel@...r.kernel.org
Subject: [PATCH 38/42] KVM: selftests: Check KVM's supported CPUID, not host
 CPUID, for XFD

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@...gle.com>
---
 .../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