Re: [PATCH v8 12/30] KVM: selftests: TDX: Add basic TDX CPUID test

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

On 8/14/2025 11:20 AM, Chenyi Qiang wrote:
>
> On 8/8/2025 4:16 AM, Sagi Shahar wrote:
>> The test reads CPUID values from inside a TD VM and compare them

compare -> compares


>> to expected values.
>>
>> The test targets CPUID values which are virtualized as "As Configured",
>> "As Configured (if Native)", "Calculated", "Fixed" and "Native"
>> according to the TDX spec.
>>
>> Co-developed-by: Isaku Yamahata <isaku.yamahata@intel.com>
>> Signed-off-by: Isaku Yamahata <isaku.yamahata@intel.com>
>> Signed-off-by: Sagi Shahar <sagis@google.com>
>> ---
>>   .../selftests/kvm/include/x86/tdx/test_util.h | 15 +++
>>   .../selftests/kvm/lib/x86/tdx/test_util.c     | 20 ++++
>>   tools/testing/selftests/kvm/x86/tdx_vm_test.c | 98 ++++++++++++++++++-
>>   3 files changed, 132 insertions(+), 1 deletion(-)
>>
>> diff --git a/tools/testing/selftests/kvm/include/x86/tdx/test_util.h b/tools/testing/selftests/kvm/include/x86/tdx/test_util.h
>> index cf11955d56d6..2af6e810ef78 100644
>> --- a/tools/testing/selftests/kvm/include/x86/tdx/test_util.h
>> +++ b/tools/testing/selftests/kvm/include/x86/tdx/test_util.h
>> @@ -9,6 +9,9 @@
>>   #define TDX_TEST_SUCCESS_PORT 0x30
>>   #define TDX_TEST_SUCCESS_SIZE 4
>>   
>> +#define TDX_TEST_REPORT_PORT 0x31
>> +#define TDX_TEST_REPORT_SIZE 4
>> +
>>   /* Port I/O direction */
>>   #define PORT_READ	0
>>   #define PORT_WRITE	1
>> @@ -77,4 +80,16 @@ void tdx_test_fatal_with_data(uint64_t error_code, uint64_t data_gpa);
>>    */
>>   void tdx_assert_error(uint64_t error);
>>   
>> +/*
>> + * Report a 32 bit value from the guest to user space using TDG.VP.VMCALL
>> + * <Instruction.IO> call. Data is reported on port TDX_TEST_REPORT_PORT.
>> + */
>> +uint64_t tdx_test_report_to_user_space(uint32_t data);
>> +
>> +/*
>> + * Read a 32 bit value from the guest in user space, sent using
>> + * tdx_test_report_to_user_space().
>> + */
>> +uint32_t tdx_test_read_report_from_guest(struct kvm_vcpu *vcpu);
>> +
>>   #endif // SELFTEST_TDX_TEST_UTIL_H
>> diff --git a/tools/testing/selftests/kvm/lib/x86/tdx/test_util.c b/tools/testing/selftests/kvm/lib/x86/tdx/test_util.c
>> index 4ccc5298ba25..f9bde114a8bc 100644
>> --- a/tools/testing/selftests/kvm/lib/x86/tdx/test_util.c
>> +++ b/tools/testing/selftests/kvm/lib/x86/tdx/test_util.c
>> @@ -104,3 +104,23 @@ void tdx_assert_error(uint64_t error)
>>   	if (error)
>>   		tdx_test_fatal(error);
>>   }
>> +
>> +uint64_t tdx_test_report_to_user_space(uint32_t data)
>> +{
>> +	/* Upcast data to match tdg_vp_vmcall_instruction_io() signature */
>> +	uint64_t data_64 = data;
>> +
>> +	return tdg_vp_vmcall_instruction_io(TDX_TEST_REPORT_PORT,
>> +					    TDX_TEST_REPORT_SIZE, PORT_WRITE,
>> +					    &data_64);
>> +}
>> +
>> +uint32_t tdx_test_read_report_from_guest(struct kvm_vcpu *vcpu)
>> +{
>> +	uint32_t res;
>> +
>> +	tdx_test_assert_io(vcpu, TDX_TEST_REPORT_PORT, 4, PORT_WRITE);
>> +	res = *(uint32_t *)((void *)vcpu->run + vcpu->run->io.data_offset);
>> +
>> +	return res;
>> +}
>> diff --git a/tools/testing/selftests/kvm/x86/tdx_vm_test.c b/tools/testing/selftests/kvm/x86/tdx_vm_test.c
>> index 97330e28f236..bbdcca358d71 100644
>> --- a/tools/testing/selftests/kvm/x86/tdx_vm_test.c
>> +++ b/tools/testing/selftests/kvm/x86/tdx_vm_test.c
>> @@ -3,6 +3,7 @@
>>   #include <signal.h>
>>   
>>   #include "kvm_util.h"
>> +#include "processor.h"
>>   #include "tdx/tdcall.h"
>>   #include "tdx/tdx.h"
>>   #include "tdx/tdx_util.h"
>> @@ -146,6 +147,99 @@ void verify_td_ioexit(void)
>>   	printf("\t ... PASSED\n");
>>   }
>>   
>> +/*
>> + * Verifies CPUID functionality by reading CPUID values in guest. The guest
>> + * will then send the values to userspace using an IO write to be checked
>> + * against the expected values.
>> + */
>> +void guest_code_cpuid(void)
>> +{
>> +	uint32_t ebx, ecx;
>> +	uint64_t err;
>> +
>> +	/* Read CPUID leaf 0x1 */
>> +	asm volatile ("cpuid"
>> +		      : "=b" (ebx), "=c" (ecx)
>> +		      : "a" (0x1)
>> +		      : "edx");
>> +
>> +	err = tdx_test_report_to_user_space(ebx);
>> +	tdx_assert_error(err);
>> +
>> +	err = tdx_test_report_to_user_space(ecx);
>> +	tdx_assert_error(err);
>> +
>> +	tdx_test_success();
>> +}
>> +
>> +void verify_td_cpuid(void)
>> +{
>> +	uint32_t guest_max_addressable_ids, host_max_addressable_ids;
>> +	const struct kvm_cpuid_entry2 *cpuid_entry;
>> +	uint32_t guest_clflush_line_size;
>> +	uint32_t guest_initial_apic_id;
>> +	uint32_t guest_sse3_enabled;
>> +	uint32_t guest_fma_enabled;
>> +	struct kvm_vcpu *vcpu;
>> +	struct kvm_vm *vm;
>> +	uint32_t ebx, ecx;
>> +
>> +	vm = td_create();
>> +	td_initialize(vm, VM_MEM_SRC_ANONYMOUS, 0);
>> +	vcpu = td_vcpu_add(vm, 0, guest_code_cpuid);
>> +	td_finalize(vm);
>> +
>> +	printf("Verifying TD CPUID:\n");
>> +
>> +	/* Wait for guest to report ebx value */
Should the comments for ebx and ecx be aligned?
>> +	tdx_run(vcpu);
>> +	ebx = tdx_test_read_report_from_guest(vcpu);
>> +
>> +	/* Wait for guest to report either ecx value or error */
>> +	tdx_run(vcpu);
>> +	ecx = tdx_test_read_report_from_guest(vcpu);
>> +
>> +	/* Wait for guest to complete execution */
>> +	tdx_run(vcpu);
>> +	tdx_test_assert_success(vcpu);
>> +
>> +	/* Verify the CPUID values received from the guest. */
>> +	printf("\t ... Verifying CPUID values from guest\n");
>> +
>> +	/* Get KVM CPUIDs for reference */
>> +	cpuid_entry = vcpu_get_cpuid_entry(vcpu, 1);
>> +	TEST_ASSERT(cpuid_entry, "CPUID entry missing\n");
>> +
>> +	host_max_addressable_ids = (cpuid_entry->ebx >> 16) & 0xFF;
>> +
>> +	guest_sse3_enabled = ecx & 0x1;  // Native
> It seems the CPUID virtualization types in this series are based on some old
> TDX module spec. The SSE3 has become fixed1 in current public 1.5 base spec.
Yes, the comment should be fixed.

Also, BIT(X86_FEATURE_XMM3.bit) could be used for the mask of sse3.
Similar for FMA below.

>
>> +	guest_clflush_line_size = (ebx >> 8) & 0xFF;  // Fixed
>> +	guest_max_addressable_ids = (ebx >> 16) & 0xFF;  // As Configured
>> +	guest_fma_enabled = (ecx >> 12) & 0x1;  // As Configured (if Native)
>> +	guest_initial_apic_id = (ebx >> 24) & 0xFF;  // Calculated
>> +
>> +	TEST_ASSERT_EQ(guest_sse3_enabled, 1);
>> +	TEST_ASSERT_EQ(guest_clflush_line_size, 8);
>> +	TEST_ASSERT_EQ(guest_max_addressable_ids, host_max_addressable_ids);
>> +
>> +	/* TODO: This only tests the native value. To properly test
>> +	 * "As Configured (if Native)" this value needs override in the
>> +	 * TD params.
>> +	 */
>> +	TEST_ASSERT_EQ(guest_fma_enabled, (cpuid_entry->ecx >> 12) & 0x1);
> FMA is configured by XFAM[2]. If we choose this feature, need to set init_vm->xfam
> which has not been used to configure features in this series yet.

Yes, the virtualization type of FMA is "XFAM & Native", since XFAM is not used
to configure FMA in this series, the value will always be 0.

Because this patch series uses the values retried via KVM_TDX_GET_CPUID as the
input values for KVM_SET_CPUID2, the comparison is still valid, no matter XFAM[2]
is set or not.

The comment needs to be update.

>
>> +
>> +	/* TODO: guest_initial_apic_id is calculated based on the number of
>> +	 * vCPUs in the TD. From the spec: "Virtual CPU index, starting from 0
>> +	 * and allocated sequentially on each successful TDH.VP.INIT"
>> +	 * To test non-trivial values either use a TD with multiple vCPUs
>> +	 * or pick a different calculated value.
>> +	 */
>> +	TEST_ASSERT_EQ(guest_initial_apic_id, 0);
>> +
>> +	kvm_vm_free(vm);
>> +	printf("\t ... PASSED\n");
>> +}
>> +
>>   int main(int argc, char **argv)
>>   {
>>   	ksft_print_header();
>> @@ -153,13 +247,15 @@ 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(3);
>> +	ksft_set_plan(4);
>>   	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),
>>   			 "verify_report_fatal_error\n");
>>   	ksft_test_result(!run_in_new_process(&verify_td_ioexit),
>>   			 "verify_td_ioexit\n");
>> +	ksft_test_result(!run_in_new_process(&verify_td_cpuid),
>> +			 "verify_td_cpuid\n");
>>   
>>   	ksft_finished();
>>   	return 0;