KVM: selftests: Move nested invalid CR3 check to its own test

vmx_tsc_adjust_test currently verifies that a nested VMLAUNCH fails with
an invalid CR3. This is irrelevant to TSC scaling, move it to a
standalone test.

Signed-off-by: Yosry Ahmed <yosry.ahmed@linux.dev>
Link: https://patch.msgid.link/20251021074736.1324328-6-yosry.ahmed@linux.dev
Signed-off-by: Sean Christopherson <seanjc@google.com>

3 files changed, 80 insertions, 10 deletions

diff --git a/tools/testing/selftests/kvm/Makefile.kvm b/tools/testing/selftests/kvm/Makefile.kvm
index 9ffa0d5c7654..5bfd242da1ca 100644
--- a/tools/testing/selftests/kvm/Makefile.kvm
+++ b/tools/testing/selftests/kvm/Makefile.kvm
@@ -91,6 +91,7 @@ TEST_GEN_PROGS_x86 += x86/msrs_test
 TEST_GEN_PROGS_x86 += x86/nested_close_kvm_test
 TEST_GEN_PROGS_x86 += x86/nested_emulation_test
 TEST_GEN_PROGS_x86 += x86/nested_exceptions_test
+TEST_GEN_PROGS_x86 += x86/nested_invalid_cr3_test
 TEST_GEN_PROGS_x86 += x86/nested_tsc_scaling_test
 TEST_GEN_PROGS_x86 += x86/platform_info_test
 TEST_GEN_PROGS_x86 += x86/pmu_counters_test
diff --git a/tools/testing/selftests/kvm/x86/nested_invalid_cr3_test.c b/tools/testing/selftests/kvm/x86/nested_invalid_cr3_test.c
new file mode 100644
index 000000000000..e839bcf5f8ad
--- /dev/null
+++ b/tools/testing/selftests/kvm/x86/nested_invalid_cr3_test.c
@@ -0,0 +1,79 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2025, Google LLC.
+ *
+ * This test verifies that L1 fails to enter L2 with an invalid CR3, and
+ * succeeds otherwise.
+ */
+#include "kvm_util.h"
+#include "vmx.h"
+#include "kselftest.h"
+
+
+#define L2_GUEST_STACK_SIZE 64
+
+static void l2_guest_code(void)
+{
+	vmcall();
+}
+
+static void l1_vmx_code(struct vmx_pages *vmx_pages)
+{
+	unsigned long l2_guest_stack[L2_GUEST_STACK_SIZE];
+	uintptr_t save_cr3;
+
+	GUEST_ASSERT(prepare_for_vmx_operation(vmx_pages));
+	GUEST_ASSERT(load_vmcs(vmx_pages));
+
+	prepare_vmcs(vmx_pages, l2_guest_code,
+		     &l2_guest_stack[L2_GUEST_STACK_SIZE]);
+
+	/* Try to run L2 with invalid CR3 and make sure it fails */
+	save_cr3 = vmreadz(GUEST_CR3);
+	vmwrite(GUEST_CR3, -1ull);
+	GUEST_ASSERT(!vmlaunch());
+	GUEST_ASSERT(vmreadz(VM_EXIT_REASON) ==
+		     (EXIT_REASON_FAILED_VMENTRY | EXIT_REASON_INVALID_STATE));
+
+	/* Now restore CR3 and make sure L2 runs successfully */
+	vmwrite(GUEST_CR3, save_cr3);
+	GUEST_ASSERT(!vmlaunch());
+	GUEST_ASSERT(vmreadz(VM_EXIT_REASON) == EXIT_REASON_VMCALL);
+
+	GUEST_DONE();
+}
+
+int main(int argc, char *argv[])
+{
+	struct kvm_vcpu *vcpu;
+	struct kvm_vm *vm;
+	vm_vaddr_t guest_gva = 0;
+
+	TEST_REQUIRE(kvm_cpu_has(X86_FEATURE_VMX));
+
+	vm = vm_create_with_one_vcpu(&vcpu, l1_vmx_code);
+	vcpu_alloc_vmx(vm, &guest_gva);
+	vcpu_args_set(vcpu, 1, guest_gva);
+
+	for (;;) {
+		struct ucall uc;
+
+		vcpu_run(vcpu);
+		TEST_ASSERT_KVM_EXIT_REASON(vcpu, KVM_EXIT_IO);
+
+		switch (get_ucall(vcpu, &uc)) {
+		case UCALL_ABORT:
+			REPORT_GUEST_ASSERT(uc);
+		case UCALL_SYNC:
+			break;
+		case UCALL_DONE:
+			goto done;
+		default:
+			TEST_FAIL("Unknown ucall %lu", uc.cmd);
+		}
+	}
+
+done:
+	kvm_vm_free(vm);
+	return 0;
+}
diff --git a/tools/testing/selftests/kvm/x86/vmx_tsc_adjust_test.c b/tools/testing/selftests/kvm/x86/vmx_tsc_adjust_test.c
index 2ceb5c78c442..2dcc0306a0d9 100644
--- a/tools/testing/selftests/kvm/x86/vmx_tsc_adjust_test.c
+++ b/tools/testing/selftests/kvm/x86/vmx_tsc_adjust_test.c
@@ -77,7 +77,6 @@ static void l1_guest_code(struct vmx_pages *vmx_pages)
 #define L2_GUEST_STACK_SIZE 64
 	unsigned long l2_guest_stack[L2_GUEST_STACK_SIZE];
 	uint32_t control;
-	uintptr_t save_cr3;
 
 	GUEST_ASSERT(rdtsc() < TSC_ADJUST_VALUE);
 	wrmsr(MSR_IA32_TSC, rdtsc() - TSC_ADJUST_VALUE);
@@ -94,15 +93,6 @@ static void l1_guest_code(struct vmx_pages *vmx_pages)
 	vmwrite(CPU_BASED_VM_EXEC_CONTROL, control);
 	vmwrite(TSC_OFFSET, TSC_OFFSET_VALUE);
 
-	/* Jump into L2.  First, test failure to load guest CR3.  */
-	save_cr3 = vmreadz(GUEST_CR3);
-	vmwrite(GUEST_CR3, -1ull);
-	GUEST_ASSERT(!vmlaunch());
-	GUEST_ASSERT(vmreadz(VM_EXIT_REASON) ==
-		     (EXIT_REASON_FAILED_VMENTRY | EXIT_REASON_INVALID_STATE));
-	check_ia32_tsc_adjust(-1 * TSC_ADJUST_VALUE);
-	vmwrite(GUEST_CR3, save_cr3);
-
 	GUEST_ASSERT(!vmlaunch());
 	GUEST_ASSERT(vmreadz(VM_EXIT_REASON) == EXIT_REASON_VMCALL);