[RFC PATCH v5 20/29] 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>
Signed-off-by: Ackerley Tng <ackerleytng@google.com>
---
 .../selftests/kvm/x86_64/tdx_vm_tests.c       | 85 +++++++++++++++++++
 1 file changed, 85 insertions(+)

diff --git a/tools/testing/selftests/kvm/x86_64/tdx_vm_tests.c b/tools/testing/selftests/kvm/x86_64/tdx_vm_tests.c
index 6935604d768b..c977223ff871 100644
--- a/tools/testing/selftests/kvm/x86_64/tdx_vm_tests.c
+++ b/tools/testing/selftests/kvm/x86_64/tdx_vm_tests.c
@@ -1062,6 +1062,90 @@ 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 ret;
+	uint64_t placeholder = 0;
+
+	/* 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,
+		TDG_VP_VMCALL_INSTRUCTION_IO_WRITE, &placeholder);
+	if (ret)
+		tdx_test_fatal(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)
+{
+	struct kvm_vm *vm;
+	struct kvm_vcpu *vcpu;
+
+	vm_vaddr_t test_page;
+	uint64_t *host_virt;
+	uint64_t first_host_read;
+	uint64_t second_host_read;
+
+	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 != NULL,
+		"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");
+
+	td_vcpu_run(vcpu);
+	TDX_TEST_CHECK_GUEST_FAILURE(vcpu);
+	TDX_TEST_ASSERT_IO(vcpu, TDX_HOST_READ_PRIVATE_MEM_PORT_TEST,
+		4, TDG_VP_VMCALL_INSTRUCTION_IO_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. */
+	td_vcpu_run(vcpu);
+	TDX_TEST_CHECK_GUEST_FAILURE(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)
 {
 	setbuf(stdout, NULL);
@@ -1084,6 +1168,7 @@ int main(int argc, char **argv)
 	run_in_new_process(&verify_mmio_reads);
 	run_in_new_process(&verify_mmio_writes);
 	run_in_new_process(&verify_td_cpuid_tdcall);
+	run_in_new_process(&verify_host_reading_private_mem);
 
 	return 0;
 }
-- 
2.43.0.472.g3155946c3a-goog