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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: Emanuele Giuseppe Esposito <eesposit@redhat.com>
Link: https://lore.kernel.org/r/20230109130605.2013555-3-eesposit@redhat.com
Co-developed-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
This commit is contained in:
Emanuele Giuseppe Esposito 2023-01-09 08:06:05 -05:00 committed by Sean Christopherson
parent 052c3b99cb
commit eb98192576
1 changed files with 55 additions and 0 deletions
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55
tools/testing/selftests/kvm/x86_64/xapic_state_test.c
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@ -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();
}