Commit cd5f3d21 authored by Sean Christopherson's avatar Sean Christopherson
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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: default avatarSean Christopherson <seanjc@google.com>
Link: https://lore.kernel.org/r/20221128225735.3291648-4-seanjc@google.com
parent 2ceade1d

tools/testing/selftests/kvm/lib/x86_64/processor.c

+12 −6
Original line number Diff line number Diff line
@@ -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);