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

[Chenyi Qiang <chenyi.qiang@intel.com>]

On 8/8/2025 4:16 AM, Sagi Shahar wrote:
> The test reads CPUID values from inside a TD VM and compare them
> 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 */
> +	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.

> +	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.

> +
> +	/* 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;