linux-kernel - [PATCH v2 1/4] KVM: selftests: Move XFD CPUID checking out of __vm_xsave_require

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Message-ID: <20221128225735.3291648-2-seanjc@google.com>
Date:   Mon, 28 Nov 2022 22:57:32 +0000
From:   Sean Christopherson <seanjc@...gle.com>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        Lei Wang <lei4.wang@...el.com>,
        Sean Christopherson <seanjc@...gle.com>
Subject: [PATCH v2 1/4] KVM: selftests: Move XFD CPUID checking out of __vm_xsave_require_permission()

From: Lei Wang <lei4.wang@...el.com>

Move the kvm_cpu_has() check on X86_FEATURE_XFD out of the helper to
enable off-by-default XSAVE-managed features and into the one test that
currenty requires XFD (XFeature Disable) support.   kvm_cpu_has() uses
kvm_get_supported_cpuid() and thus caches KVM_GET_SUPPORTED_CPUID, and so
using kvm_cpu_has() before ARCH_REQ_XCOMP_GUEST_PERM effectively results
in the test caching stale values, e.g. subsequent checks on AMX_TILE will
get false negatives.

Although off-by-default features are nonsensical without XFD, checking
for XFD virtualization prior to enabling such features isn't strictly
required.

Signed-off-by: Lei Wang <lei4.wang@...el.com>
Fixes: 7fbb653e01fd ("KVM: selftests: Check KVM's supported CPUID, not host CPUID, for XFD")
Link: https://lore.kernel.org/r/20221125023839.315207-1-lei4.wang@intel.com
[sean: add Fixes, reword changelog]
Signed-off-by: Sean Christopherson <seanjc@...gle.com>
---
 tools/testing/selftests/kvm/lib/x86_64/processor.c | 2 --
 tools/testing/selftests/kvm/x86_64/amx_test.c      | 1 +
 2 files changed, 1 insertion(+), 2 deletions(-)

diff --git a/tools/testing/selftests/kvm/lib/x86_64/processor.c b/tools/testing/selftests/kvm/lib/x86_64/processor.c
index d532c20c74fd..aac7b32a794b 100644
--- a/tools/testing/selftests/kvm/lib/x86_64/processor.c
+++ b/tools/testing/selftests/kvm/lib/x86_64/processor.c
@@ -563,8 +563,6 @@ void __vm_xsave_require_permission(int bit, const char *name)
 		.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);
diff --git a/tools/testing/selftests/kvm/x86_64/amx_test.c b/tools/testing/selftests/kvm/x86_64/amx_test.c
index 21de6ae42086..1256c7faadd3 100644
--- a/tools/testing/selftests/kvm/x86_64/amx_test.c
+++ b/tools/testing/selftests/kvm/x86_64/amx_test.c
@@ -254,6 +254,7 @@ int main(int argc, char *argv[])
 	/* Create VM */
 	vm = vm_create_with_one_vcpu(&vcpu, guest_code);
 
+	TEST_REQUIRE(kvm_cpu_has(X86_FEATURE_XFD));
 	TEST_REQUIRE(kvm_cpu_has(X86_FEATURE_XSAVE));
 	TEST_REQUIRE(kvm_cpu_has(X86_FEATURE_AMX_TILE));
 	TEST_REQUIRE(kvm_cpu_has(X86_FEATURE_XTILECFG));
-- 
2.38.1.584.g0f3c55d4c2-goog