From: Michal Luczaj <mhal@xxxxxxx>
Add a test to verify that userspace can't change a vCPU's x2APIC ID by
abusing KVM_SET_LAPIC. KVM models the x2APIC ID (and x2APIC LDR) as
readonly, and silently ignores userspace attempts to change the x2APIC ID
for backwards compatibility.
Signed-off-by: Michal Luczaj <mhal@xxxxxxx>
[sean: write changelog, add to existing test]
Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
---
.../selftests/kvm/x86_64/xapic_state_test.c | 28 +++++++++++++++++++
1 file changed, 28 insertions(+)
diff --git a/tools/testing/selftests/kvm/x86_64/xapic_state_test.c b/tools/testing/selftests/kvm/x86_64/xapic_state_test.c
index 69849acd95b0..618cd2442390 100644
--- a/tools/testing/selftests/kvm/x86_64/xapic_state_test.c
+++ b/tools/testing/selftests/kvm/x86_64/xapic_state_test.c
@@ -184,6 +184,33 @@ static void test_apic_id(void)
kvm_vm_free(vm);
}
+static void test_x2apic_id(void)
+{
+ struct kvm_lapic_state lapic = {};
+ struct kvm_vcpu *vcpu;
+ struct kvm_vm *vm;
+ int i;
+
+ vm = vm_create_with_one_vcpu(&vcpu, NULL);
+ vcpu_set_msr(vcpu, MSR_IA32_APICBASE, MSR_IA32_APICBASE_ENABLE | X2APIC_ENABLE);
+
+ /*
+ * Try stuffing a modified x2APIC ID, KVM should ignore the value and
+ * always return the vCPU's default/readonly x2APIC ID.
+ */
+ for (i = 0; i <= 0xff; i++) {
+ *(u32 *)(lapic.regs + APIC_ID) = i << 24;
+ *(u32 *)(lapic.regs + APIC_SPIV) = APIC_SPIV_APIC_ENABLED;
+ vcpu_ioctl(vcpu, KVM_SET_LAPIC, &lapic);
+
+ vcpu_ioctl(vcpu, KVM_GET_LAPIC, &lapic);
+ TEST_ASSERT(*((u32 *)&lapic.regs[APIC_ID]) == vcpu->id << 24,
+ "x2APIC ID should be fully readonly");
+ }
+
+ kvm_vm_free(vm);
+}
+
int main(int argc, char *argv[])
{
struct xapic_vcpu x = {
@@ -211,4 +238,5 @@ int main(int argc, char *argv[])
kvm_vm_free(vm);
test_apic_id();
+ test_x2apic_id();
}
--
2.46.0.rc2.264.g509ed76dc8-goog
