Disallow using kvm_get_supported_cpuid() and thus caching KVM's supported
CPUID info before enabling XSAVE-managed features that are off-by-default
and must be enabled by ARCH_REQ_XCOMP_GUEST_PERM. Caching the supported
CPUID before all XSAVE features are enabled can result in false negatives
due to testing features that were cached before they were enabled.
Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
---
.../selftests/kvm/lib/x86_64/processor.c | 18 ++++++++++++------
1 file changed, 12 insertions(+), 6 deletions(-)
diff --git a/tools/testing/selftests/kvm/lib/x86_64/processor.c b/tools/testing/selftests/kvm/lib/x86_64/processor.c
index 23067465c035..1d3829e652e6 100644
--- a/tools/testing/selftests/kvm/lib/x86_64/processor.c
+++ b/tools/testing/selftests/kvm/lib/x86_64/processor.c
@@ -601,21 +601,24 @@ void vcpu_arch_free(struct kvm_vcpu *vcpu)
free(vcpu->cpuid);
}
+/* Do not use kvm_supported_cpuid directly except for validity checks. */
+static void *kvm_supported_cpuid;
+
const struct kvm_cpuid2 *kvm_get_supported_cpuid(void)
{
- static struct kvm_cpuid2 *cpuid;
int kvm_fd;
- if (cpuid)
- return cpuid;
+ if (kvm_supported_cpuid)
+ return kvm_supported_cpuid;
- cpuid = allocate_kvm_cpuid2(MAX_NR_CPUID_ENTRIES);
+ kvm_supported_cpuid = allocate_kvm_cpuid2(MAX_NR_CPUID_ENTRIES);
kvm_fd = open_kvm_dev_path_or_exit();
- kvm_ioctl(kvm_fd, KVM_GET_SUPPORTED_CPUID, cpuid);
+ kvm_ioctl(kvm_fd, KVM_GET_SUPPORTED_CPUID,
+ (struct kvm_cpuid2 *)kvm_supported_cpuid);
close(kvm_fd);
- return cpuid;
+ return kvm_supported_cpuid;
}
static uint32_t __kvm_cpu_has(const struct kvm_cpuid2 *cpuid,
@@ -684,6 +687,9 @@ void __vm_xsave_require_permission(int bit, const char *name)
.addr = (unsigned long) &bitmask
};
+ TEST_ASSERT(!kvm_supported_cpuid,
+ "kvm_get_supported_cpuid() cannot be used before ARCH_REQ_XCOMP_GUEST_PERM");
+
kvm_fd = open_kvm_dev_path_or_exit();
rc = __kvm_ioctl(kvm_fd, KVM_GET_DEVICE_ATTR, &attr);
close(kvm_fd);
--
2.38.1.584.g0f3c55d4c2-goog
