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

From: Binbin Wu
Date: Mon Mar 04 2024 - 04:18:06 EST



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