Re: [PATCH v8 22/30] KVM: selftests: TDX: Add TDG.VP.INFO test

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

On 8/8/2025 4:16 AM, Sagi Shahar wrote:
> From: Roger Wang <runanwang@google.com>
>
> Adds a test for TDG.VP.INFO.
>
> Introduce __tdx_module_call() that does needed shuffling from function
> parameters to registers used by the TDCALL instruction that is used by the
> guest to communicate with the TDX module. The first function parameter is
> the leaf number indicating which guest side function should be run, for
> example, TDG.VP.INFO.

I think __tdx_hypercall() can be combined into __tdx_module_call(), it's just
another leaf TDG.VP.VMCALL for tdcall. To avoid two copies of assembly code
doing similar things?



>
> The guest uses new __tdx_module_call() to call TDG.VP.INFO to obtain TDX
> TD execution environment information from the TDX module. All returned
> registers are passed back to the host that verifies values for
> correctness.
>
> Co-developed-by: Sagi Shahar <sagis@google.com>
> Signed-off-by: Sagi Shahar <sagis@google.com>
> Signed-off-by: Roger Wang <runanwang@google.com>
> Signed-off-by: Sagi Shahar <sagis@google.com>
> ---
>   .../selftests/kvm/include/x86/tdx/tdcall.h    |  19 +++
>   .../selftests/kvm/include/x86/tdx/tdx.h       |   5 +
>   .../selftests/kvm/lib/x86/tdx/tdcall.S        |  68 +++++++++
>   tools/testing/selftests/kvm/lib/x86/tdx/tdx.c |  27 ++++
>   tools/testing/selftests/kvm/x86/tdx_vm_test.c | 133 +++++++++++++++++-
>   5 files changed, 251 insertions(+), 1 deletion(-)
>
> diff --git a/tools/testing/selftests/kvm/include/x86/tdx/tdcall.h b/tools/testing/selftests/kvm/include/x86/tdx/tdcall.h
> index e7440f7fe259..ab1a97a82fa9 100644
> --- a/tools/testing/selftests/kvm/include/x86/tdx/tdcall.h
> +++ b/tools/testing/selftests/kvm/include/x86/tdx/tdcall.h
> @@ -32,4 +32,23 @@ struct tdx_hypercall_args {
>   /* Used to request services from the VMM */
>   u64 __tdx_hypercall(struct tdx_hypercall_args *args, unsigned long flags);
>   
> +/*
> + * Used to gather the output registers values of the TDCALL and SEAMCALL
> + * instructions when requesting services from the TDX module.
> + *
> + * This is a software only structure and not part of the TDX module/VMM ABI.
> + */
> +struct tdx_module_output {
> +	u64 rcx;
> +	u64 rdx;
> +	u64 r8;
> +	u64 r9;
> +	u64 r10;
> +	u64 r11;
> +};
> +
> +/* Used to communicate with the TDX module */
> +u64 __tdx_module_call(u64 fn, u64 rcx, u64 rdx, u64 r8, u64 r9,
> +		      struct tdx_module_output *out);
> +
>   #endif // SELFTESTS_TDX_TDCALL_H
> diff --git a/tools/testing/selftests/kvm/include/x86/tdx/tdx.h b/tools/testing/selftests/kvm/include/x86/tdx/tdx.h
> index 060158cb046b..801ca879664e 100644
> --- a/tools/testing/selftests/kvm/include/x86/tdx/tdx.h
> +++ b/tools/testing/selftests/kvm/include/x86/tdx/tdx.h
> @@ -6,6 +6,8 @@
>   
>   #include "kvm_util.h"
>   
> +#define TDG_VP_INFO 1
> +
>   #define TDG_VP_VMCALL_GET_TD_VM_CALL_INFO 0x10000
>   #define TDG_VP_VMCALL_REPORT_FATAL_ERROR 0x10003
>   
> @@ -31,5 +33,8 @@ uint64_t tdg_vp_vmcall_ve_request_mmio_write(uint64_t address, uint64_t size,
>   uint64_t tdg_vp_vmcall_instruction_cpuid(uint32_t eax, uint32_t ecx,
>   					 uint32_t *ret_eax, uint32_t *ret_ebx,
>   					 uint32_t *ret_ecx, uint32_t *ret_edx);
> +uint64_t tdg_vp_info(uint64_t *rcx, uint64_t *rdx,
> +		     uint64_t *r8, uint64_t *r9,
> +		     uint64_t *r10, uint64_t *r11);
>   
>   #endif // SELFTEST_TDX_TDX_H
> diff --git a/tools/testing/selftests/kvm/lib/x86/tdx/tdcall.S b/tools/testing/selftests/kvm/lib/x86/tdx/tdcall.S
> index b10769d1d557..c393a0fb35be 100644
> --- a/tools/testing/selftests/kvm/lib/x86/tdx/tdcall.S
> +++ b/tools/testing/selftests/kvm/lib/x86/tdx/tdcall.S
> @@ -91,5 +91,73 @@ __tdx_hypercall:
>   	pop %rbp
>   	ret
>   
> +#define TDX_MODULE_rcx 0 /* offsetof(struct tdx_module_output, rcx) */
> +#define TDX_MODULE_rdx 8 /* offsetof(struct tdx_module_output, rdx) */
> +#define TDX_MODULE_r8 16 /* offsetof(struct tdx_module_output, r8) */
> +#define TDX_MODULE_r9 24 /* offsetof(struct tdx_module_output, r9) */
> +#define TDX_MODULE_r10 32 /* offsetof(struct tdx_module_output, r10) */
> +#define TDX_MODULE_r11 40 /* offsetof(struct tdx_module_output, r11) */
> +
> +.globl __tdx_module_call
> +.type __tdx_module_call, @function
> +__tdx_module_call:
> +	/* Set up stack frame */
> +	push %rbp
> +	movq %rsp, %rbp
> +
> +	/* Callee-saved, so preserve it */
> +	push %r12
> +
> +	/*
> +	 * Push output pointer to stack.
> +	 * After the operation, it will be fetched into R12 register.
> +	 */
> +	push %r9
> +
> +	/* Mangle function call ABI into TDCALL/SEAMCALL ABI: */
> +	/* Move Leaf ID to RAX */
> +	mov %rdi, %rax
> +	/* Move input 4 to R9 */
> +	mov %r8,  %r9
> +	/* Move input 3 to R8 */
> +	mov %rcx, %r8
> +	/* Move input 1 to RCX */
> +	mov %rsi, %rcx
> +	/* Leave input param 2 in RDX */
> +
> +	tdcall
> +
> +	/*
> +	 * Fetch output pointer from stack to R12 (It is used
> +	 * as temporary storage)
> +	 */
> +	pop %r12
> +
> +	/*
> +	 * Since this macro can be invoked with NULL as an output pointer,
> +	 * check if caller provided an output struct before storing output
> +	 * registers.
> +	 *
> +	 * Update output registers, even if the call failed (RAX != 0).
> +	 * Other registers may contain details of the failure.
> +	 */
> +	test %r12, %r12
> +	jz .Lno_output_struct
> +
> +	/* Copy result registers to output struct: */
> +	movq %rcx, TDX_MODULE_rcx(%r12)
> +	movq %rdx, TDX_MODULE_rdx(%r12)
> +	movq %r8,  TDX_MODULE_r8(%r12)
> +	movq %r9,  TDX_MODULE_r9(%r12)
> +	movq %r10, TDX_MODULE_r10(%r12)
> +	movq %r11, TDX_MODULE_r11(%r12)
> +
> +.Lno_output_struct:
> +	/* Restore the state of R12 register */
> +	pop %r12
> +
> +	pop %rbp
> +	ret
> +
>   /* Disable executable stack */
>   .section .note.GNU-stack,"",%progbits
> diff --git a/tools/testing/selftests/kvm/lib/x86/tdx/tdx.c b/tools/testing/selftests/kvm/lib/x86/tdx/tdx.c
> index fb391483d2fa..ab6fd3d7ae4b 100644
> --- a/tools/testing/selftests/kvm/lib/x86/tdx/tdx.c
> +++ b/tools/testing/selftests/kvm/lib/x86/tdx/tdx.c
> @@ -162,3 +162,30 @@ uint64_t tdg_vp_vmcall_instruction_cpuid(uint32_t eax, uint32_t ecx,
>   
>   	return ret;
>   }
> +
> +uint64_t tdg_vp_info(uint64_t *rcx, uint64_t *rdx,
> +		     uint64_t *r8, uint64_t *r9,
> +		     uint64_t *r10, uint64_t *r11)
> +{
> +	struct tdx_module_output out;
> +	uint64_t ret;
> +
> +	memset(&out, 0, sizeof(struct tdx_module_output));
> +
> +	ret = __tdx_module_call(TDG_VP_INFO, 0, 0, 0, 0, &out);
> +
> +	if (rcx)
> +		*rcx = out.rcx;
> +	if (rdx)
> +		*rdx = out.rdx;
> +	if (r8)
> +		*r8 = out.r8;
> +	if (r9)
> +		*r9 = out.r9;
> +	if (r10)
> +		*r10 = out.r10;
> +	if (r11)
> +		*r11 = out.r11;
> +
> +	return ret;
> +}
> diff --git a/tools/testing/selftests/kvm/x86/tdx_vm_test.c b/tools/testing/selftests/kvm/x86/tdx_vm_test.c
> index b6ef0348746c..82acc17a66ab 100644
> --- a/tools/testing/selftests/kvm/x86/tdx_vm_test.c
> +++ b/tools/testing/selftests/kvm/x86/tdx_vm_test.c
> @@ -1038,6 +1038,135 @@ void verify_host_reading_private_mem(void)
>   	printf("\t ... PASSED\n");
>   }
>   
> +/*
> + * Do a TDG.VP.INFO call from the guest
> + */
> +void guest_tdcall_vp_info(void)
> +{
> +	uint64_t rcx, rdx, r8, r9, r10, r11;
> +	uint64_t err;
> +
> +	err = tdg_vp_info(&rcx, &rdx, &r8, &r9, &r10, &r11);
> +	tdx_assert_error(err);
> +
> +	/* return values to user space host */
> +	err = tdx_test_report_64bit_to_user_space(rcx);
> +	tdx_assert_error(err);
> +
> +	err = tdx_test_report_64bit_to_user_space(rdx);
> +	tdx_assert_error(err);
> +
> +	err = tdx_test_report_64bit_to_user_space(r8);
> +	tdx_assert_error(err);
> +
> +	err = tdx_test_report_64bit_to_user_space(r9);
> +	tdx_assert_error(err);
> +
> +	err = tdx_test_report_64bit_to_user_space(r10);
> +	tdx_assert_error(err);
> +
> +	err = tdx_test_report_64bit_to_user_space(r11);
> +	tdx_assert_error(err);
> +
> +	tdx_test_success();
> +}
> +
> +/*
> + * TDG.VP.INFO call from the guest. Verify the right values are returned
> + */
> +void verify_tdcall_vp_info(void)
> +{
> +	const struct kvm_cpuid_entry2 *cpuid_entry;
> +	uint32_t ret_num_vcpus, ret_max_vcpus;
> +	uint64_t rcx, rdx, r8, r9, r10, r11;
> +	const int num_vcpus = 2;
> +	struct kvm_vcpu *vcpus[num_vcpus];
> +	uint64_t attributes;
> +	struct kvm_vm *vm;
> +	int gpa_bits = -1;
> +	uint32_t i;
> +
> +	vm = td_create();
> +
> +#define TDX_TDPARAM_ATTR_SEPT_VE_DISABLE_BIT	BIT(28)
> +	/* Setting attributes parameter used by TDH.MNG.INIT to 0x10000000 */
> +	attributes = TDX_TDPARAM_ATTR_SEPT_VE_DISABLE_BIT;
> +
> +	td_initialize(vm, VM_MEM_SRC_ANONYMOUS, attributes);
> +
> +	for (i = 0; i < num_vcpus; i++)
> +		vcpus[i] = td_vcpu_add(vm, i, guest_tdcall_vp_info);
> +
> +	td_finalize(vm);
> +
> +	printf("Verifying TDG.VP.INFO call:\n");
> +
> +	/* Get KVM CPUIDs for reference */
> +
> +	for (i = 0; i < num_vcpus; i++) {
> +		struct kvm_vcpu *vcpu = vcpus[i];
> +
> +		cpuid_entry = vcpu_get_cpuid_entry(vcpu, 0x80000008);
> +		TEST_ASSERT(cpuid_entry, "CPUID entry missing\n");
> +		gpa_bits = (cpuid_entry->eax & GENMASK(23, 16)) >> 16;
> +		TEST_ASSERT_EQ((1UL << (gpa_bits - 1)), tdx_s_bit);
> +
> +		/* Wait for guest to report rcx value */
> +		tdx_run(vcpu);
> +		rcx = tdx_test_read_64bit_report_from_guest(vcpu);
> +
> +		/* Wait for guest to report rdx value */
> +		tdx_run(vcpu);
> +		rdx = tdx_test_read_64bit_report_from_guest(vcpu);
> +
> +		/* Wait for guest to report r8 value */
> +		tdx_run(vcpu);
> +		r8 = tdx_test_read_64bit_report_from_guest(vcpu);
> +
> +		/* Wait for guest to report r9 value */
> +		tdx_run(vcpu);
> +		r9 = tdx_test_read_64bit_report_from_guest(vcpu);
> +
> +		/* Wait for guest to report r10 value */
> +		tdx_run(vcpu);
> +		r10 = tdx_test_read_64bit_report_from_guest(vcpu);
> +
> +		/* Wait for guest to report r11 value */
> +		tdx_run(vcpu);
> +		r11 = tdx_test_read_64bit_report_from_guest(vcpu);
> +
> +		ret_num_vcpus = r8 & 0xFFFFFFFF;
> +		ret_max_vcpus = (r8 >> 32) & 0xFFFFFFFF;
> +
> +		/* first bits 5:0 of rcx represent the GPAW */
> +		TEST_ASSERT_EQ(rcx & 0x3F, gpa_bits);
> +		/* next 63:6 bits of rcx is reserved and must be 0 */
> +		TEST_ASSERT_EQ(rcx >> 6, 0);
> +		TEST_ASSERT_EQ(rdx, attributes);
> +		TEST_ASSERT_EQ(ret_num_vcpus, num_vcpus);
> +		TEST_ASSERT_EQ(ret_max_vcpus, vm_check_cap(vm, KVM_CAP_MAX_VCPUS));
> +		/* VCPU_INDEX = i */
> +		TEST_ASSERT_EQ(r9, i);
> +		/*
> +		 * verify reserved bits are 0
> +		 * r10 bit 0 (SYS_RD) indicates that the TDG.SYS.RD/RDM/RDALL
> +		 * functions are available and can be either 0 or 1.
> +		 */
> +		TEST_ASSERT_EQ(r10 & ~1, 0);
> +		TEST_ASSERT_EQ(r11, 0);
> +
> +		/* Wait for guest to complete execution */
> +		tdx_run(vcpu);
> +
> +		tdx_test_assert_success(vcpu);
> +
> +		printf("\t ... Guest completed run on VCPU=%u\n", i);
> +	}
> +
> +	kvm_vm_free(vm);
> +	printf("\t ... PASSED\n");
> +}
> +
>   int main(int argc, char **argv)
>   {
>   	ksft_print_header();
> @@ -1045,7 +1174,7 @@ 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(14);
> +	ksft_set_plan(15);
>   	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),
> @@ -1074,6 +1203,8 @@ int main(int argc, char **argv)
>   			 "verify_td_cpuid_tdcall\n");
>   	ksft_test_result(!run_in_new_process(&verify_host_reading_private_mem),
>   			 "verify_host_reading_private_mem\n");
> +	ksft_test_result(!run_in_new_process(&verify_tdcall_vp_info),
> +			 "verify_tdcall_vp_info\n");
>   
>   	ksft_finished();
>   	return 0;