Commit cd5a0c2f authored by Sean Christopherson's avatar Sean Christopherson
Browse files

KVM: selftests: Manage CPUID array in Hyper-V CPUID test's core helper 



Allocate, get, and free the CPUID array in the Hyper-V CPUID test in the
test's core helper, instead of copy+pasting code at each call site.  In
addition to deduplicating a small amount of code, restricting visibility
of the array to a single invocation of the core test prevents "leaking" an
array across test cases.  Passing in @vcpu to the helper will also allow
pivoting on VM-scoped information without needing to pass more booleans,
e.g. to conditionally assert on features that require an in-kernel APIC.

To avoid use-after-free bugs due to overzealous and careless developers,
opportunstically add a comment to explain that the system-scoped helper
caches the Hyper-V CPUID entries, i.e. that the caller is not responsible
for freeing the memory.

Cc: Vitaly Kuznetsov <vkuznets@redhat.com>
Reviewed-by: default avatarVitaly Kuznetsov <vkuznets@redhat.com>
Link: https://lore.kernel.org/r/20250118003454.2619573-4-seanjc@google.com


Signed-off-by: default avatarSean Christopherson <seanjc@google.com>
parent 0b6db0dc

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

+17 −13
Original line number Diff line number Diff line
@@ -41,13 +41,18 @@ static bool smt_possible(void) 
	return res;

}



static void test_hv_cpuid(const struct kvm_cpuid2 *hv_cpuid_entries,

			  bool evmcs_expected)

static void test_hv_cpuid(struct kvm_vcpu *vcpu, bool evmcs_expected)

{

	const struct kvm_cpuid2 *hv_cpuid_entries;

	int i;

	int nent_expected = 10;

	u32 test_val;



	if (vcpu)

		hv_cpuid_entries = vcpu_get_supported_hv_cpuid(vcpu);

	else

		hv_cpuid_entries = kvm_get_supported_hv_cpuid();



	TEST_ASSERT(hv_cpuid_entries->nent == nent_expected,

		    "KVM_GET_SUPPORTED_HV_CPUID should return %d entries"

		    " (returned %d)",
@@ -109,6 +114,13 @@ static void test_hv_cpuid(const struct kvm_cpuid2 *hv_cpuid_entries, 
		 *	entry->edx);

		 */

	}



	/*

	 * Note, the CPUID array returned by the system-scoped helper is a one-

	 * time allocation, i.e. must not be freed.

	 */

	if (vcpu)

		free((void *)hv_cpuid_entries);

}



static void test_hv_cpuid_e2big(struct kvm_vm *vm, struct kvm_vcpu *vcpu)
@@ -129,7 +141,6 @@ static void test_hv_cpuid_e2big(struct kvm_vm *vm, struct kvm_vcpu *vcpu) 
int main(int argc, char *argv[])

{

	struct kvm_vm *vm;

	const struct kvm_cpuid2 *hv_cpuid_entries;

	struct kvm_vcpu *vcpu;



	TEST_REQUIRE(kvm_has_cap(KVM_CAP_HYPERV_CPUID));
@@ -138,10 +149,7 @@ int main(int argc, char *argv[]) 


	/* Test vCPU ioctl version */

	test_hv_cpuid_e2big(vm, vcpu);



	hv_cpuid_entries = vcpu_get_supported_hv_cpuid(vcpu);

	test_hv_cpuid(hv_cpuid_entries, false);

	free((void *)hv_cpuid_entries);

	test_hv_cpuid(vcpu, false);



	if (!kvm_cpu_has(X86_FEATURE_VMX) ||

	    !kvm_has_cap(KVM_CAP_HYPERV_ENLIGHTENED_VMCS)) {
@@ -149,9 +157,7 @@ int main(int argc, char *argv[]) 
		goto do_sys;

	}

	vcpu_enable_evmcs(vcpu);

	hv_cpuid_entries = vcpu_get_supported_hv_cpuid(vcpu);

	test_hv_cpuid(hv_cpuid_entries, true);

	free((void *)hv_cpuid_entries);

	test_hv_cpuid(vcpu, true);



do_sys:

	/* Test system ioctl version */
@@ -161,9 +167,7 @@ int main(int argc, char *argv[]) 
	}



	test_hv_cpuid_e2big(vm, NULL);



	hv_cpuid_entries = kvm_get_supported_hv_cpuid();

	test_hv_cpuid(hv_cpuid_entries, kvm_cpu_has(X86_FEATURE_VMX));

	test_hv_cpuid(NULL, kvm_cpu_has(X86_FEATURE_VMX));



out:

	kvm_vm_free(vm);