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

[Binbin Wu <binbin.wu@linux.intel.com>]

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@google.com>
>>
>> Verifies TDVMCALL<INSTRUCTION.IO> READ and WRITE operations.
>>
>> Signed-off-by: Erdem Aktas <erdemaktas@google.com>
>> Signed-off-by: Sagi Shahar <sagis@google.com>
>> Signed-off-by: Ackerley Tng <ackerleytng@google.com>
>> Signed-off-by: Ryan Afranji <afranji@google.com>
>> ---
>>   .../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
>>
>>