From cd5f3d210095347e9d40a9a1d464f5ee0bb5d7f2 Mon Sep 17 00:00:00 2001 From: Sean Christopherson Date: Mon, 28 Nov 2022 22:57:34 +0000 Subject: [PATCH] KVM: selftests: Disallow "get supported CPUID" before REQ_XCOMP_GUEST_PERM 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 Link: https://lore.kernel.org/r/20221128225735.3291648-4-seanjc@google.com --- tools/testing/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 2306746..1d3829e 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); -- 2.7.4