Commit eb981925 authored by Emanuele Giuseppe Esposito's avatar Emanuele Giuseppe Esposito Committed by Sean Christopherson
Browse files

KVM: selftests: Verify APIC_ID is set when forcing x2APIC=>xAPIC transition 



Add a sub-test to verify that KVM stuffs the APIC_ID when userspace forces
a transition from x2APIC to xAPIC without first disabling the APIC.  Such
a transition is architecturally disallowed (WRMSR will #GP), but needs to
be handled by KVM to allow userspace to emulate RESET (ignoring that
userspace should also stuff local APIC state on RESET).

Signed-off-by: default avatarEmanuele Giuseppe Esposito <eesposit@redhat.com>
Link: https://lore.kernel.org/r/20230109130605.2013555-3-eesposit@redhat.com


Co-developed-by: default avatarSean Christopherson <seanjc@google.com>
Signed-off-by: default avatarSean Christopherson <seanjc@google.com>
parent 052c3b99

tools/testing/selftests/kvm/x86_64/xapic_state_test.c

+55 −0
Original line number Diff line number Diff line
@@ -132,6 +132,59 @@ static void test_icr(struct xapic_vcpu *x) 
	__test_icr(x, -1ull & ~APIC_DM_FIXED_MASK);

}



static void __test_apic_id(struct kvm_vcpu *vcpu, uint64_t apic_base)

{

	uint32_t apic_id, expected;

	struct kvm_lapic_state xapic;



	vcpu_set_msr(vcpu, MSR_IA32_APICBASE, apic_base);



	vcpu_ioctl(vcpu, KVM_GET_LAPIC, &xapic);



	expected = apic_base & X2APIC_ENABLE ? vcpu->id : vcpu->id << 24;

	apic_id = *((u32 *)&xapic.regs[APIC_ID]);



	TEST_ASSERT(apic_id == expected,

		    "APIC_ID not set back to %s format; wanted = %x, got = %x",

		    (apic_base & X2APIC_ENABLE) ? "x2APIC" : "xAPIC",

		    expected, apic_id);

}



/*

 * Verify that KVM switches the APIC_ID between xAPIC and x2APIC when userspace

 * stuffs MSR_IA32_APICBASE.  Setting the APIC_ID when x2APIC is enabled and

 * when the APIC transitions for DISABLED to ENABLED is architectural behavior

 * (on Intel), whereas the x2APIC => xAPIC transition behavior is KVM ABI since

 * attempted to transition from x2APIC to xAPIC without disabling the APIC is

 * architecturally disallowed.

 */

static void test_apic_id(void)

{

	const uint32_t NR_VCPUS = 3;

	struct kvm_vcpu *vcpus[NR_VCPUS];

	uint64_t apic_base;

	struct kvm_vm *vm;

	int i;



	vm = vm_create_with_vcpus(NR_VCPUS, NULL, vcpus);

	vm_enable_cap(vm, KVM_CAP_X2APIC_API, KVM_X2APIC_API_USE_32BIT_IDS);



	for (i = 0; i < NR_VCPUS; i++) {

		apic_base = vcpu_get_msr(vcpus[i], MSR_IA32_APICBASE);



		TEST_ASSERT(apic_base & MSR_IA32_APICBASE_ENABLE,

			    "APIC not in ENABLED state at vCPU RESET");

		TEST_ASSERT(!(apic_base & X2APIC_ENABLE),

			    "APIC not in xAPIC mode at vCPU RESET");



		__test_apic_id(vcpus[i], apic_base);

		__test_apic_id(vcpus[i], apic_base | X2APIC_ENABLE);

		__test_apic_id(vcpus[i], apic_base);

	}



	kvm_vm_free(vm);

}



int main(int argc, char *argv[])

{

	struct xapic_vcpu x = {
@@ -157,4 +210,6 @@ int main(int argc, char *argv[]) 
	virt_pg_map(vm, APIC_DEFAULT_GPA, APIC_DEFAULT_GPA);

	test_icr(&x);

	kvm_vm_free(vm);



	test_apic_id();

}