[PATCH v8 21/30] KVM: selftests: TDX: Verify the behavior when host consumes a TD private memory

[Sagi Shahar <sagis@google.com>]

From: Ryan Afranji <afranji@google.com>

The test checks that host can only read fixed values when trying to
access the guest's private memory.

Signed-off-by: Ryan Afranji <afranji@google.com>
Signed-off-by: Sagi Shahar <sagis@google.com>
---
 tools/testing/selftests/kvm/x86/tdx_vm_test.c | 83 ++++++++++++++++++-
 1 file changed, 82 insertions(+), 1 deletion(-)

diff --git a/tools/testing/selftests/kvm/x86/tdx_vm_test.c b/tools/testing/selftests/kvm/x86/tdx_vm_test.c
index 2f75f12d2a44..b6ef0348746c 100644
--- a/tools/testing/selftests/kvm/x86/tdx_vm_test.c
+++ b/tools/testing/selftests/kvm/x86/tdx_vm_test.c
@@ -959,6 +959,85 @@ void verify_td_cpuid_tdcall(void)
 	printf("\t ... PASSED\n");
 }
 
+/*
+ * Shared variables between guest and host for host reading private mem test
+ */
+static uint64_t tdx_test_host_read_private_mem_addr;
+#define TDX_HOST_READ_PRIVATE_MEM_PORT_TEST 0x53
+
+void guest_host_read_priv_mem(void)
+{
+	uint64_t placeholder = 0;
+	uint64_t ret;
+
+	/* Set value */
+	*((uint32_t *)tdx_test_host_read_private_mem_addr) = 0xABCD;
+
+	/* Exit so host can read value */
+	ret = tdg_vp_vmcall_instruction_io(TDX_HOST_READ_PRIVATE_MEM_PORT_TEST,
+					   4, PORT_WRITE, &placeholder);
+	tdx_assert_error(ret);
+
+	/* Update guest_var's value and have host reread it. */
+	*((uint32_t *)tdx_test_host_read_private_mem_addr) = 0xFEDC;
+
+	tdx_test_success();
+}
+
+void verify_host_reading_private_mem(void)
+{
+	uint64_t second_host_read;
+	uint64_t first_host_read;
+	struct kvm_vcpu *vcpu;
+	vm_vaddr_t test_page;
+	uint64_t *host_virt;
+	struct kvm_vm *vm;
+
+	vm = td_create();
+	td_initialize(vm, VM_MEM_SRC_ANONYMOUS, 0);
+	vcpu = td_vcpu_add(vm, 0, guest_host_read_priv_mem);
+
+	test_page = vm_vaddr_alloc_page(vm);
+	TEST_ASSERT(test_page < BIT_ULL(32),
+		    "Test address should fit in 32 bits so it can be sent to the guest");
+
+	host_virt = addr_gva2hva(vm, test_page);
+	TEST_ASSERT(host_virt,
+		    "Guest address not found in guest memory regions\n");
+
+	tdx_test_host_read_private_mem_addr = test_page;
+	sync_global_to_guest(vm, tdx_test_host_read_private_mem_addr);
+
+	td_finalize(vm);
+
+	printf("Verifying host's behavior when reading TD private memory:\n");
+
+	tdx_run(vcpu);
+	tdx_test_assert_io(vcpu, TDX_HOST_READ_PRIVATE_MEM_PORT_TEST,
+			   4, PORT_WRITE);
+	printf("\t ... Guest's variable contains 0xABCD\n");
+
+	/* Host reads guest's variable. */
+	first_host_read = *host_virt;
+	printf("\t ... Host's read attempt value: %lu\n", first_host_read);
+
+	/* Guest updates variable and host rereads it. */
+	tdx_run(vcpu);
+	printf("\t ... Guest's variable updated to 0xFEDC\n");
+
+	second_host_read = *host_virt;
+	printf("\t ... Host's second read attempt value: %lu\n",
+	       second_host_read);
+
+	TEST_ASSERT(first_host_read == second_host_read,
+		    "Host did not read a fixed pattern\n");
+
+	printf("\t ... Fixed pattern was returned to the host\n");
+
+	kvm_vm_free(vm);
+	printf("\t ... PASSED\n");
+}
+
 int main(int argc, char **argv)
 {
 	ksft_print_header();
@@ -966,7 +1045,7 @@ int main(int argc, char **argv)
 	if (!is_tdx_enabled())
 		ksft_exit_skip("TDX is not supported by the KVM. Exiting.\n");
 
-	ksft_set_plan(13);
+	ksft_set_plan(14);
 	ksft_test_result(!run_in_new_process(&verify_td_lifecycle),
 			 "verify_td_lifecycle\n");
 	ksft_test_result(!run_in_new_process(&verify_report_fatal_error),
@@ -993,6 +1072,8 @@ int main(int argc, char **argv)
 			 "verify_mmio_writes\n");
 	ksft_test_result(!run_in_new_process(&verify_td_cpuid_tdcall),
 			 "verify_td_cpuid_tdcall\n");
+	ksft_test_result(!run_in_new_process(&verify_host_reading_private_mem),
+			 "verify_host_reading_private_mem\n");
 
 	ksft_finished();
 	return 0;
-- 
2.51.0.rc0.155.g4a0f42376b-goog