Re: [RFC PATCH v5 10/29] KVM: selftests: TDX: Adding test case for TDX port IO

Binbin Wu <binbin.wu@xxxxxxxxxxxxxxx> · Mon, 4 Mar 2024 17:16:53 +0800

On 3/4/2024 10:19 AM, Yan Zhao wrote:
On Tue, Dec 12, 2023 at 12:46:25PM -0800, Sagi Shahar wrote:
From: Erdem Aktas <erdemaktas@xxxxxxxxxx>

Verifies TDVMCALL<INSTRUCTION.IO> READ and WRITE operations.

Signed-off-by: Erdem Aktas <erdemaktas@xxxxxxxxxx>
Signed-off-by: Sagi Shahar <sagis@xxxxxxxxxx>
Signed-off-by: Ackerley Tng <ackerleytng@xxxxxxxxxx>
Signed-off-by: Ryan Afranji <afranji@xxxxxxxxxx>
---
  .../kvm/include/x86_64/tdx/test_util.h        | 34 ++++++++
  .../selftests/kvm/x86_64/tdx_vm_tests.c       | 82 +++++++++++++++++++
  2 files changed, 116 insertions(+)

diff --git a/tools/testing/selftests/kvm/include/x86_64/tdx/test_util.h b/tools/testing/selftests/kvm/include/x86_64/tdx/test_util.h
index 6d69921136bd..95a5d5be7f0b 100644
--- a/tools/testing/selftests/kvm/include/x86_64/tdx/test_util.h
+++ b/tools/testing/selftests/kvm/include/x86_64/tdx/test_util.h
@@ -9,6 +9,40 @@
  #define TDX_TEST_SUCCESS_PORT 0x30
  #define TDX_TEST_SUCCESS_SIZE 4
  
+/**
+ * Assert that some IO operation involving tdg_vp_vmcall_instruction_io() was
+ * called in the guest.
+ */
+#define TDX_TEST_ASSERT_IO(VCPU, PORT, SIZE, DIR)			\
+	do {								\
+		TEST_ASSERT((VCPU)->run->exit_reason == KVM_EXIT_IO,	\
+			"Got exit_reason other than KVM_EXIT_IO: %u (%s)\n", \
+			(VCPU)->run->exit_reason,			\
+			exit_reason_str((VCPU)->run->exit_reason));	\
+									\
+		TEST_ASSERT(((VCPU)->run->exit_reason == KVM_EXIT_IO) && \
+			((VCPU)->run->io.port == (PORT)) &&		\
+			((VCPU)->run->io.size == (SIZE)) &&		\
+			((VCPU)->run->io.direction == (DIR)),		\
+			"Got unexpected IO exit values: %u (%s) %d %d %d\n", \
+			(VCPU)->run->exit_reason,			\
+			exit_reason_str((VCPU)->run->exit_reason),	\
+			(VCPU)->run->io.port, (VCPU)->run->io.size,	\
+			(VCPU)->run->io.direction);			\
+	} while (0)
+
+/**
+ * Check and report if there was some failure in the guest, either an exception
+ * like a triple fault, or if a tdx_test_fatal() was hit.
+ */
+#define TDX_TEST_CHECK_GUEST_FAILURE(VCPU)				\
+	do {								\
+		if ((VCPU)->run->exit_reason == KVM_EXIT_SYSTEM_EVENT)	\
+			TEST_FAIL("Guest reported error. error code: %lld (0x%llx)\n", \
+				(VCPU)->run->system_event.data[1],	\
+				(VCPU)->run->system_event.data[1]);	\
+	} while (0)
+
  /**
   * Assert that tdx_test_success() was called in the guest.
   */
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 8638c7bbedaa..75467c407ca7 100644
--- a/tools/testing/selftests/kvm/x86_64/tdx_vm_tests.c
+++ b/tools/testing/selftests/kvm/x86_64/tdx_vm_tests.c
@@ -2,6 +2,7 @@
  
  #include <signal.h>
  #include "kvm_util_base.h"
+#include "tdx/tdcall.h"
  #include "tdx/tdx.h"
  #include "tdx/tdx_util.h"
  #include "tdx/test_util.h"
@@ -74,6 +75,86 @@ void verify_report_fatal_error(void)
  	printf("\t ... PASSED\n");
  }
  
+#define TDX_IOEXIT_TEST_PORT 0x50
+
+/*
+ * Verifies IO functionality by writing a |value| to a predefined port.
+ * Verifies that the read value is |value| + 1 from the same port.
+ * If all the tests are passed then write a value to port TDX_TEST_PORT
+ */
+void guest_ioexit(void)
+{
+	uint64_t data_out, data_in, delta;
+	uint64_t ret;
+
+	data_out = 0xAB;
+	ret = tdg_vp_vmcall_instruction_io(TDX_IOEXIT_TEST_PORT, 1,
+					TDG_VP_VMCALL_INSTRUCTION_IO_WRITE,
+					&data_out);
+	if (ret)
+		tdx_test_fatal(ret);
+
+	ret = tdg_vp_vmcall_instruction_io(TDX_IOEXIT_TEST_PORT, 1,
+					TDG_VP_VMCALL_INSTRUCTION_IO_READ,
+					&data_in);
+	if (ret)
+		tdx_test_fatal(ret);
+
+	delta = data_in - data_out;
+	if (delta != 1)
+		tdx_test_fatal(ret);
+
+	tdx_test_success();
+}
+
+void verify_td_ioexit(void)
+{
+	struct kvm_vm *vm;
+	struct kvm_vcpu *vcpu;
+
+	uint32_t port_data;
+
+	vm = td_create();
+	td_initialize(vm, VM_MEM_SRC_ANONYMOUS, 0);
+	vcpu = td_vcpu_add(vm, 0, guest_ioexit);
+	td_finalize(vm);
+
+	printf("Verifying TD IO Exit:\n");
+
+	/* Wait for guest to do a IO write */
+	td_vcpu_run(vcpu);
+	TDX_TEST_CHECK_GUEST_FAILURE(vcpu);
This check is a vain, because the first VMExit from vcpu run is always
KVM_EXIT_IO caused by tdg_vp_vmcall_instruction_io().

I think tdg_vp_vmcall_instruction_io() could fail if RCX (GPR select) 
doesn't
meet the requirement (some bits must be 0).
Although RCX is set by guest code (in selftest, it set in __tdx_hypercall())
and it will not trigger the error, it still can be used as a guard to make
sure guest doesn't pass a invalid RCX.




+	TDX_TEST_ASSERT_IO(vcpu, TDX_IOEXIT_TEST_PORT, 1,
+			TDG_VP_VMCALL_INSTRUCTION_IO_WRITE);
+	port_data = *(uint8_t *)((void *)vcpu->run + vcpu->run->io.data_offset);
+
+	printf("\t ... IO WRITE: OK\n");
So,  even if there's an error in emulating writing of TDX_IOEXIT_TEST_PORT,
and guest would then find a failure and trigger tdx_test_fatal(), this line
will still print "IO WRITE: OK", which is not right.

+
+	/*
+	 * Wait for the guest to do a IO read. Provide the previous written data
+	 * + 1 back to the guest
+	 */
+	td_vcpu_run(vcpu);
+	TDX_TEST_CHECK_GUEST_FAILURE(vcpu);
This check is a vain, too, as in  write case.

+	TDX_TEST_ASSERT_IO(vcpu, TDX_IOEXIT_TEST_PORT, 1,
+			TDG_VP_VMCALL_INSTRUCTION_IO_READ);
+	*(uint8_t *)((void *)vcpu->run + vcpu->run->io.data_offset) = port_data + 1;
+
+	printf("\t ... IO READ: OK\n");
Same as in write case, this line should not be printed until after guest
finishing checking return code.

+
+	/*
+	 * Wait for the guest to complete execution successfully. The read
+	 * value is checked within the guest.
+	 */
+	td_vcpu_run(vcpu);
+	TDX_TEST_CHECK_GUEST_FAILURE(vcpu);
+	TDX_TEST_ASSERT_SUCCESS(vcpu);
+
+	printf("\t ... IO verify read/write values: OK\n");
+	kvm_vm_free(vm);
+	printf("\t ... PASSED\n");
+}
+
  int main(int argc, char **argv)
  {
  	setbuf(stdout, NULL);
@@ -85,6 +166,7 @@ int main(int argc, char **argv)
  
  	run_in_new_process(&verify_td_lifecycle);
  	run_in_new_process(&verify_report_fatal_error);
+	run_in_new_process(&verify_td_ioexit);
  
  	return 0;
  }
--
2.43.0.472.g3155946c3a-goog










