KVM: selftests: Use canonical $(ARCH) paths for KVM selftests directories

Use the kernel's canonical $(ARCH) paths instead of the raw target triple
for KVM selftests directories.  KVM selftests are quite nearly the only
place in the entire kernel that using the target triple for directories,
tools/testing/selftests/drivers/s390x being the lone holdout.

Using the kernel's preferred nomenclature eliminates the minor, but
annoying, friction of having to translate to KVM's selftests directories,
e.g. for pattern matching, opening files, running selftests, etc.

Opportunsitically delete file comments that reference the full path of the
file, as they are obviously prone to becoming stale, and serve no known
purpose.

Reviewed-by: Muhammad Usama Anjum <usama.anjum@collabora.com>
Acked-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
Acked-by: Andrew Jones <ajones@ventanamicro.com>
Link: https://lore.kernel.org/r/20241128005547.4077116-16-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>

1 files changed, 288 insertions, 0 deletions

diff --git a/tools/testing/selftests/kvm/x86/nested_exceptions_test.c b/tools/testing/selftests/kvm/x86/nested_exceptions_test.c
new file mode 100644
index 000000000000..3eb0313ffa39
--- /dev/null
+++ b/tools/testing/selftests/kvm/x86/nested_exceptions_test.c
@@ -0,0 +1,288 @@
+// SPDX-License-Identifier: GPL-2.0-only
+#include "test_util.h"
+#include "kvm_util.h"
+#include "processor.h"
+#include "vmx.h"
+#include "svm_util.h"
+
+#define L2_GUEST_STACK_SIZE 256
+
+/*
+ * Arbitrary, never shoved into KVM/hardware, just need to avoid conflict with
+ * the "real" exceptions used, #SS/#GP/#DF (12/13/8).
+ */
+#define FAKE_TRIPLE_FAULT_VECTOR	0xaa
+
+/* Arbitrary 32-bit error code injected by this test. */
+#define SS_ERROR_CODE 0xdeadbeef
+
+/*
+ * Bit '0' is set on Intel if the exception occurs while delivering a previous
+ * event/exception.  AMD's wording is ambiguous, but presumably the bit is set
+ * if the exception occurs while delivering an external event, e.g. NMI or INTR,
+ * but not for exceptions that occur when delivering other exceptions or
+ * software interrupts.
+ *
+ * Note, Intel's name for it, "External event", is misleading and much more
+ * aligned with AMD's behavior, but the SDM is quite clear on its behavior.
+ */
+#define ERROR_CODE_EXT_FLAG	BIT(0)
+
+/*
+ * Bit '1' is set if the fault occurred when looking up a descriptor in the
+ * IDT, which is the case here as the IDT is empty/NULL.
+ */
+#define ERROR_CODE_IDT_FLAG	BIT(1)
+
+/*
+ * The #GP that occurs when vectoring #SS should show the index into the IDT
+ * for #SS, plus have the "IDT flag" set.
+ */
+#define GP_ERROR_CODE_AMD ((SS_VECTOR * 8) | ERROR_CODE_IDT_FLAG)
+#define GP_ERROR_CODE_INTEL ((SS_VECTOR * 8) | ERROR_CODE_IDT_FLAG | ERROR_CODE_EXT_FLAG)
+
+/*
+ * Intel and AMD both shove '0' into the error code on #DF, regardless of what
+ * led to the double fault.
+ */
+#define DF_ERROR_CODE 0
+
+#define INTERCEPT_SS		(BIT_ULL(SS_VECTOR))
+#define INTERCEPT_SS_DF		(INTERCEPT_SS | BIT_ULL(DF_VECTOR))
+#define INTERCEPT_SS_GP_DF	(INTERCEPT_SS_DF | BIT_ULL(GP_VECTOR))
+
+static void l2_ss_pending_test(void)
+{
+	GUEST_SYNC(SS_VECTOR);
+}
+
+static void l2_ss_injected_gp_test(void)
+{
+	GUEST_SYNC(GP_VECTOR);
+}
+
+static void l2_ss_injected_df_test(void)
+{
+	GUEST_SYNC(DF_VECTOR);
+}
+
+static void l2_ss_injected_tf_test(void)
+{
+	GUEST_SYNC(FAKE_TRIPLE_FAULT_VECTOR);
+}
+
+static void svm_run_l2(struct svm_test_data *svm, void *l2_code, int vector,
+		       uint32_t error_code)
+{
+	struct vmcb *vmcb = svm->vmcb;
+	struct vmcb_control_area *ctrl = &vmcb->control;
+
+	vmcb->save.rip = (u64)l2_code;
+	run_guest(vmcb, svm->vmcb_gpa);
+
+	if (vector == FAKE_TRIPLE_FAULT_VECTOR)
+		return;
+
+	GUEST_ASSERT_EQ(ctrl->exit_code, (SVM_EXIT_EXCP_BASE + vector));
+	GUEST_ASSERT_EQ(ctrl->exit_info_1, error_code);
+}
+
+static void l1_svm_code(struct svm_test_data *svm)
+{
+	struct vmcb_control_area *ctrl = &svm->vmcb->control;
+	unsigned long l2_guest_stack[L2_GUEST_STACK_SIZE];
+
+	generic_svm_setup(svm, NULL, &l2_guest_stack[L2_GUEST_STACK_SIZE]);
+	svm->vmcb->save.idtr.limit = 0;
+	ctrl->intercept |= BIT_ULL(INTERCEPT_SHUTDOWN);
+
+	ctrl->intercept_exceptions = INTERCEPT_SS_GP_DF;
+	svm_run_l2(svm, l2_ss_pending_test, SS_VECTOR, SS_ERROR_CODE);
+	svm_run_l2(svm, l2_ss_injected_gp_test, GP_VECTOR, GP_ERROR_CODE_AMD);
+
+	ctrl->intercept_exceptions = INTERCEPT_SS_DF;
+	svm_run_l2(svm, l2_ss_injected_df_test, DF_VECTOR, DF_ERROR_CODE);
+
+	ctrl->intercept_exceptions = INTERCEPT_SS;
+	svm_run_l2(svm, l2_ss_injected_tf_test, FAKE_TRIPLE_FAULT_VECTOR, 0);
+	GUEST_ASSERT_EQ(ctrl->exit_code, SVM_EXIT_SHUTDOWN);
+
+	GUEST_DONE();
+}
+
+static void vmx_run_l2(void *l2_code, int vector, uint32_t error_code)
+{
+	GUEST_ASSERT(!vmwrite(GUEST_RIP, (u64)l2_code));
+
+	GUEST_ASSERT_EQ(vector == SS_VECTOR ? vmlaunch() : vmresume(), 0);
+
+	if (vector == FAKE_TRIPLE_FAULT_VECTOR)
+		return;
+
+	GUEST_ASSERT_EQ(vmreadz(VM_EXIT_REASON), EXIT_REASON_EXCEPTION_NMI);
+	GUEST_ASSERT_EQ((vmreadz(VM_EXIT_INTR_INFO) & 0xff), vector);
+	GUEST_ASSERT_EQ(vmreadz(VM_EXIT_INTR_ERROR_CODE), error_code);
+}
+
+static void l1_vmx_code(struct vmx_pages *vmx)
+{
+	unsigned long l2_guest_stack[L2_GUEST_STACK_SIZE];
+
+	GUEST_ASSERT_EQ(prepare_for_vmx_operation(vmx), true);
+
+	GUEST_ASSERT_EQ(load_vmcs(vmx), true);
+
+	prepare_vmcs(vmx, NULL, &l2_guest_stack[L2_GUEST_STACK_SIZE]);
+	GUEST_ASSERT_EQ(vmwrite(GUEST_IDTR_LIMIT, 0), 0);
+
+	/*
+	 * VMX disallows injecting an exception with error_code[31:16] != 0,
+	 * and hardware will never generate a VM-Exit with bits 31:16 set.
+	 * KVM should likewise truncate the "bad" userspace value.
+	 */
+	GUEST_ASSERT_EQ(vmwrite(EXCEPTION_BITMAP, INTERCEPT_SS_GP_DF), 0);
+	vmx_run_l2(l2_ss_pending_test, SS_VECTOR, (u16)SS_ERROR_CODE);
+	vmx_run_l2(l2_ss_injected_gp_test, GP_VECTOR, GP_ERROR_CODE_INTEL);
+
+	GUEST_ASSERT_EQ(vmwrite(EXCEPTION_BITMAP, INTERCEPT_SS_DF), 0);
+	vmx_run_l2(l2_ss_injected_df_test, DF_VECTOR, DF_ERROR_CODE);
+
+	GUEST_ASSERT_EQ(vmwrite(EXCEPTION_BITMAP, INTERCEPT_SS), 0);
+	vmx_run_l2(l2_ss_injected_tf_test, FAKE_TRIPLE_FAULT_VECTOR, 0);
+	GUEST_ASSERT_EQ(vmreadz(VM_EXIT_REASON), EXIT_REASON_TRIPLE_FAULT);
+
+	GUEST_DONE();
+}
+
+static void __attribute__((__flatten__)) l1_guest_code(void *test_data)
+{
+	if (this_cpu_has(X86_FEATURE_SVM))
+		l1_svm_code(test_data);
+	else
+		l1_vmx_code(test_data);
+}
+
+static void assert_ucall_vector(struct kvm_vcpu *vcpu, int vector)
+{
+	struct ucall uc;
+
+	TEST_ASSERT_KVM_EXIT_REASON(vcpu, KVM_EXIT_IO);
+
+	switch (get_ucall(vcpu, &uc)) {
+	case UCALL_SYNC:
+		TEST_ASSERT(vector == uc.args[1],
+			    "Expected L2 to ask for %d, got %ld", vector, uc.args[1]);
+		break;
+	case UCALL_DONE:
+		TEST_ASSERT(vector == -1,
+			    "Expected L2 to ask for %d, L2 says it's done", vector);
+		break;
+	case UCALL_ABORT:
+		REPORT_GUEST_ASSERT(uc);
+		break;
+	default:
+		TEST_FAIL("Expected L2 to ask for %d, got unexpected ucall %lu", vector, uc.cmd);
+	}
+}
+
+static void queue_ss_exception(struct kvm_vcpu *vcpu, bool inject)
+{
+	struct kvm_vcpu_events events;
+
+	vcpu_events_get(vcpu, &events);
+
+	TEST_ASSERT(!events.exception.pending,
+		    "Vector %d unexpectedlt pending", events.exception.nr);
+	TEST_ASSERT(!events.exception.injected,
+		    "Vector %d unexpectedly injected", events.exception.nr);
+
+	events.flags = KVM_VCPUEVENT_VALID_PAYLOAD;
+	events.exception.pending = !inject;
+	events.exception.injected = inject;
+	events.exception.nr = SS_VECTOR;
+	events.exception.has_error_code = true;
+	events.exception.error_code = SS_ERROR_CODE;
+	vcpu_events_set(vcpu, &events);
+}
+
+/*
+ * Verify KVM_{G,S}ET_EVENTS play nice with pending vs. injected exceptions
+ * when an exception is being queued for L2.  Specifically, verify that KVM
+ * honors L1 exception intercept controls when a #SS is pending/injected,
+ * triggers a #GP on vectoring the #SS, morphs to #DF if #GP isn't intercepted
+ * by L1, and finally causes (nested) SHUTDOWN if #DF isn't intercepted by L1.
+ */
+int main(int argc, char *argv[])
+{
+	vm_vaddr_t nested_test_data_gva;
+	struct kvm_vcpu_events events;
+	struct kvm_vcpu *vcpu;
+	struct kvm_vm *vm;
+
+	TEST_REQUIRE(kvm_has_cap(KVM_CAP_EXCEPTION_PAYLOAD));
+	TEST_REQUIRE(kvm_cpu_has(X86_FEATURE_SVM) || kvm_cpu_has(X86_FEATURE_VMX));
+
+	vm = vm_create_with_one_vcpu(&vcpu, l1_guest_code);
+	vm_enable_cap(vm, KVM_CAP_EXCEPTION_PAYLOAD, -2ul);
+
+	if (kvm_cpu_has(X86_FEATURE_SVM))
+		vcpu_alloc_svm(vm, &nested_test_data_gva);
+	else
+		vcpu_alloc_vmx(vm, &nested_test_data_gva);
+
+	vcpu_args_set(vcpu, 1, nested_test_data_gva);
+
+	/* Run L1 => L2.  L2 should sync and request #SS. */
+	vcpu_run(vcpu);
+	assert_ucall_vector(vcpu, SS_VECTOR);
+
+	/* Pend #SS and request immediate exit.  #SS should still be pending. */
+	queue_ss_exception(vcpu, false);
+	vcpu->run->immediate_exit = true;
+	vcpu_run_complete_io(vcpu);
+
+	/* Verify the pending events comes back out the same as it went in. */
+	vcpu_events_get(vcpu, &events);
+	TEST_ASSERT_EQ(events.flags & KVM_VCPUEVENT_VALID_PAYLOAD,
+			KVM_VCPUEVENT_VALID_PAYLOAD);
+	TEST_ASSERT_EQ(events.exception.pending, true);
+	TEST_ASSERT_EQ(events.exception.nr, SS_VECTOR);
+	TEST_ASSERT_EQ(events.exception.has_error_code, true);
+	TEST_ASSERT_EQ(events.exception.error_code, SS_ERROR_CODE);
+
+	/*
+	 * Run for real with the pending #SS, L1 should get a VM-Exit due to
+	 * #SS interception and re-enter L2 to request #GP (via injected #SS).
+	 */
+	vcpu->run->immediate_exit = false;
+	vcpu_run(vcpu);
+	assert_ucall_vector(vcpu, GP_VECTOR);
+
+	/*
+	 * Inject #SS, the #SS should bypass interception and cause #GP, which
+	 * L1 should intercept before KVM morphs it to #DF.  L1 should then
+	 * disable #GP interception and run L2 to request #DF (via #SS => #GP).
+	 */
+	queue_ss_exception(vcpu, true);
+	vcpu_run(vcpu);
+	assert_ucall_vector(vcpu, DF_VECTOR);
+
+	/*
+	 * Inject #SS, the #SS should bypass interception and cause #GP, which
+	 * L1 is no longer interception, and so should see a #DF VM-Exit.  L1
+	 * should then signal that is done.
+	 */
+	queue_ss_exception(vcpu, true);
+	vcpu_run(vcpu);
+	assert_ucall_vector(vcpu, FAKE_TRIPLE_FAULT_VECTOR);
+
+	/*
+	 * Inject #SS yet again.  L1 is not intercepting #GP or #DF, and so
+	 * should see nested TRIPLE_FAULT / SHUTDOWN.
+	 */
+	queue_ss_exception(vcpu, true);
+	vcpu_run(vcpu);
+	assert_ucall_vector(vcpu, -1);
+
+	kvm_vm_free(vm);
+}