KVM: selftests: Rework platform_info_test to actually verify #GP

Rework platform_info_test to actually handle and verify the expected #GP
on RDMSR when the associated KVM capability is disabled.  Currently, the
test _deliberately_ doesn't handle the #GP, and instead lets it escalated
to a triple fault shutdown.

In addition to verifying that KVM generates the correct fault, handling
the #GP will be necessary (without even more shenanigans) when a future
change to the core KVM selftests library configures the IDT and exception
handlers by default (the test subtly relies on the IDT limit being '0').

Link: https://lore.kernel.org/r/20240314232637.2538648-7-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>

diff --git a/tools/testing/selftests/kvm/x86_64/platform_info_test.c b/tools/testing/selftests/kvm/x86_64/platform_info_test.c
index a6be98dbe6549707f5f8caef6aad95c8647f8c6a..cdca3579b3cdae7ec3e08e6a0640dc3464d2ae74 100644 (file)
--- a/tools/testing/selftests/kvm/x86_64/platform_info_test.c
+++ b/tools/testing/selftests/kvm/x86_64/platform_info_test.c
@@ -24,40 +24,18 @@
 static void guest_code(void)
 {
        uint64_t msr_platform_info;
+       uint8_t vector;
 
-       for (;;) {
-               msr_platform_info = rdmsr(MSR_PLATFORM_INFO);
-               GUEST_ASSERT_EQ(msr_platform_info & MSR_PLATFORM_INFO_MAX_TURBO_RATIO,
-                               MSR_PLATFORM_INFO_MAX_TURBO_RATIO);
-               GUEST_SYNC(0);
-               asm volatile ("inc %r11");
-       }
-}
-
-static void test_msr_platform_info_enabled(struct kvm_vcpu *vcpu)
-{
-       struct ucall uc;
+       GUEST_SYNC(true);
+       msr_platform_info = rdmsr(MSR_PLATFORM_INFO);
+       GUEST_ASSERT_EQ(msr_platform_info & MSR_PLATFORM_INFO_MAX_TURBO_RATIO,
+                       MSR_PLATFORM_INFO_MAX_TURBO_RATIO);
 
-       vm_enable_cap(vcpu->vm, KVM_CAP_MSR_PLATFORM_INFO, true);
-       vcpu_run(vcpu);
-       TEST_ASSERT_KVM_EXIT_REASON(vcpu, KVM_EXIT_IO);
-
-       switch (get_ucall(vcpu, &uc)) {
-       case UCALL_SYNC:
-               break;
-       case UCALL_ABORT:
-               REPORT_GUEST_ASSERT(uc);
-       default:
-               TEST_FAIL("Unexpected ucall %lu", uc.cmd);
-               break;
-       }
-}
+       GUEST_SYNC(false);
+       vector = rdmsr_safe(MSR_PLATFORM_INFO, &msr_platform_info);
+       GUEST_ASSERT_EQ(vector, GP_VECTOR);
 
-static void test_msr_platform_info_disabled(struct kvm_vcpu *vcpu)
-{
-       vm_enable_cap(vcpu->vm, KVM_CAP_MSR_PLATFORM_INFO, false);
-       vcpu_run(vcpu);
-       TEST_ASSERT_KVM_EXIT_REASON(vcpu, KVM_EXIT_SHUTDOWN);
+       GUEST_DONE();
 }
 
 int main(int argc, char *argv[])
@@ -65,16 +43,38 @@ int main(int argc, char *argv[])
        struct kvm_vcpu *vcpu;
        struct kvm_vm *vm;
        uint64_t msr_platform_info;
+       struct ucall uc;
 
        TEST_REQUIRE(kvm_has_cap(KVM_CAP_MSR_PLATFORM_INFO));
 
        vm = vm_create_with_one_vcpu(&vcpu, guest_code);
 
+       vm_init_descriptor_tables(vm);
+       vcpu_init_descriptor_tables(vcpu);
+
        msr_platform_info = vcpu_get_msr(vcpu, MSR_PLATFORM_INFO);
        vcpu_set_msr(vcpu, MSR_PLATFORM_INFO,
                     msr_platform_info | MSR_PLATFORM_INFO_MAX_TURBO_RATIO);
-       test_msr_platform_info_enabled(vcpu);
-       test_msr_platform_info_disabled(vcpu);
+
+       for (;;) {
+               vcpu_run(vcpu);
+               TEST_ASSERT_KVM_EXIT_REASON(vcpu, KVM_EXIT_IO);
+
+               switch (get_ucall(vcpu, &uc)) {
+               case UCALL_SYNC:
+                       vm_enable_cap(vm, KVM_CAP_MSR_PLATFORM_INFO, uc.args[1]);
+                       break;
+               case UCALL_DONE:
+                       goto done;
+               case UCALL_ABORT:
+                       REPORT_GUEST_ASSERT(uc);
+               default:
+                       TEST_FAIL("Unexpected ucall %lu", uc.cmd);
+                       break;
+               }
+       }
+
+done:
        vcpu_set_msr(vcpu, MSR_PLATFORM_INFO, msr_platform_info);
 
        kvm_vm_free(vm);