Commit 824d2273 authored by Sean Christopherson's avatar Sean Christopherson
Browse files

KVM: selftests: Add a CPUID testcase for KVM_SET_CPUID2 with runtime updates 

Add a CPUID testcase to verify that KVM allows KVM_SET_CPUID2 after (or in
conjunction with) runtime updates.  This is a regression test for the bug
introduced by commit 93da6af3 ("KVM: x86: Defer runtime updates of
dynamic CPUID bits until CPUID emulation"), where KVM would incorrectly
reject KVM_SET_CPUID due to a not handling a pending runtime update on the
current CPUID, resulting in a false mismatch between the "old" and "new"
CPUID entries.

Link: https://lore.kernel.org/all/20251128123202.68424a95@imammedo
Link: https://patch.msgid.link/20251202015049.1167490-3-seanjc@google.com


Signed-off-by: default avatarSean Christopherson <seanjc@google.com>
parent e2b43fb2

tools/testing/selftests/kvm/x86/cpuid_test.c

+15 −0
Original line number Diff line number Diff line
@@ -155,6 +155,7 @@ struct kvm_cpuid2 *vcpu_alloc_cpuid(struct kvm_vm *vm, vm_vaddr_t *p_gva, struct 
static void set_cpuid_after_run(struct kvm_vcpu *vcpu)

{

	struct kvm_cpuid_entry2 *ent;

	struct kvm_sregs sregs;

	int rc;

	u32 eax, ebx, x;
@@ -162,6 +163,20 @@ static void set_cpuid_after_run(struct kvm_vcpu *vcpu) 
	rc = __vcpu_set_cpuid(vcpu);

	TEST_ASSERT(!rc, "Setting unmodified CPUID after KVM_RUN failed: %d", rc);



	/*

	 * Toggle CR4 bits that affect dynamic CPUID feature flags to verify

	 * setting unmodified CPUID succeeds with runtime CPUID updates.

	 */

	vcpu_sregs_get(vcpu, &sregs);

	if (kvm_cpu_has(X86_FEATURE_XSAVE))

		sregs.cr4 ^= X86_CR4_OSXSAVE;

	if (kvm_cpu_has(X86_FEATURE_PKU))

		sregs.cr4 ^= X86_CR4_PKE;

	vcpu_sregs_set(vcpu, &sregs);



	rc = __vcpu_set_cpuid(vcpu);

	TEST_ASSERT(!rc, "Setting unmodified CPUID after KVM_RUN failed: %d", rc);



	/* Changing CPU features is forbidden */

	ent = vcpu_get_cpuid_entry(vcpu, 0x7);

	ebx = ent->ebx;