Re: [RFC PATCH v5 18/29] KVM: selftests: TDX: Add TDX MMIO writes test

[Yan Zhao]

On Tue, Dec 12, 2023 at 12:46:33PM -0800, Sagi Shahar wrote:
> The test verifies MMIO writes of various sizes from the guest to the host.
> 
> Signed-off-by: Sagi Shahar <sagis@xxxxxxxxxx>
> Signed-off-by: Ackerley Tng <ackerleytng@xxxxxxxxxx>
> Signed-off-by: Ryan Afranji <afranji@xxxxxxxxxx>
> ---
>  .../selftests/kvm/include/x86_64/tdx/tdx.h    |  2 +
>  .../selftests/kvm/lib/x86_64/tdx/tdx.c        | 14 +++
>  .../selftests/kvm/x86_64/tdx_vm_tests.c       | 85 +++++++++++++++++++
>  3 files changed, 101 insertions(+)
> 
> diff --git a/tools/testing/selftests/kvm/include/x86_64/tdx/tdx.h b/tools/testing/selftests/kvm/include/x86_64/tdx/tdx.h
> index 13ce60df5684..502b670ea699 100644
> --- a/tools/testing/selftests/kvm/include/x86_64/tdx/tdx.h
> +++ b/tools/testing/selftests/kvm/include/x86_64/tdx/tdx.h
> @@ -25,5 +25,7 @@ uint64_t tdg_vp_vmcall_instruction_wrmsr(uint64_t index, uint64_t value);
>  uint64_t tdg_vp_vmcall_instruction_hlt(uint64_t interrupt_blocked_flag);
>  uint64_t tdg_vp_vmcall_ve_request_mmio_read(uint64_t address, uint64_t size,
>  					uint64_t *data_out);
> +uint64_t tdg_vp_vmcall_ve_request_mmio_write(uint64_t address, uint64_t size,
> +					uint64_t data_in);
>  
>  #endif // SELFTEST_TDX_TDX_H
> diff --git a/tools/testing/selftests/kvm/lib/x86_64/tdx/tdx.c b/tools/testing/selftests/kvm/lib/x86_64/tdx/tdx.c
> index b19f07ebc0e7..f4afa09f7e3d 100644
> --- a/tools/testing/selftests/kvm/lib/x86_64/tdx/tdx.c
> +++ b/tools/testing/selftests/kvm/lib/x86_64/tdx/tdx.c
> @@ -143,3 +143,17 @@ uint64_t tdg_vp_vmcall_ve_request_mmio_read(uint64_t address, uint64_t size,
>  
>  	return ret;
>  }
> +
> +uint64_t tdg_vp_vmcall_ve_request_mmio_write(uint64_t address, uint64_t size,
> +					uint64_t data_in)
> +{
> +	struct tdx_hypercall_args args = {
> +		.r11 = TDG_VP_VMCALL_VE_REQUEST_MMIO,
> +		.r12 = size,
> +		.r13 = TDG_VP_VMCALL_VE_REQUEST_MMIO_WRITE,
> +		.r14 = address,
> +		.r15 = data_in,
> +	};
> +
> +	return __tdx_hypercall(&args, 0);
> +}
> 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 48902b69d13e..5e28ba828a92 100644
> --- a/tools/testing/selftests/kvm/x86_64/tdx_vm_tests.c
> +++ b/tools/testing/selftests/kvm/x86_64/tdx_vm_tests.c
> @@ -885,6 +885,90 @@ void verify_mmio_reads(void)
>  	printf("\t ... PASSED\n");
>  }
>  
> +void guest_mmio_writes(void)
> +{
> +	uint64_t ret;
> +
> +	ret = tdg_vp_vmcall_ve_request_mmio_write(TDX_MMIO_TEST_ADDR, 1, 0x12);
> +	if (ret)
> +		tdx_test_fatal(ret);
> +
> +	ret = tdg_vp_vmcall_ve_request_mmio_write(TDX_MMIO_TEST_ADDR, 2, 0x1234);
> +	if (ret)
> +		tdx_test_fatal(ret);
> +
> +	ret = tdg_vp_vmcall_ve_request_mmio_write(TDX_MMIO_TEST_ADDR, 4, 0x12345678);
> +	if (ret)
> +		tdx_test_fatal(ret);
> +
> +	ret = tdg_vp_vmcall_ve_request_mmio_write(TDX_MMIO_TEST_ADDR, 8, 0x1234567890ABCDEF);
> +	if (ret)
> +		tdx_test_fatal(ret);
> +
> +	// Write across page boundary.
> +	ret = tdg_vp_vmcall_ve_request_mmio_write(PAGE_SIZE - 1, 8, 0);
> +	if (ret)
> +		tdx_test_fatal(ret);
> +
> +	tdx_test_success();
> +}
> +
> +/*
> + * Varifies guest MMIO writes.
> + */
> +void verify_mmio_writes(void)
> +{
> +	struct kvm_vm *vm;
> +	struct kvm_vcpu *vcpu;
> +
> +	uint8_t byte_1;
> +	uint16_t byte_2;
> +	uint32_t byte_4;
> +	uint64_t byte_8;
> +
> +	vm = td_create();
> +	td_initialize(vm, VM_MEM_SRC_ANONYMOUS, 0);
> +	vcpu = td_vcpu_add(vm, 0, guest_mmio_writes);
> +	td_finalize(vm);
> +
> +	printf("Verifying TD MMIO writes:\n");
> +
> +	td_vcpu_run(vcpu);
> +	TDX_TEST_CHECK_GUEST_FAILURE(vcpu);
> +	TDX_TEST_ASSERT_MMIO(vcpu, TDX_MMIO_TEST_ADDR, 1, TDG_VP_VMCALL_VE_REQUEST_MMIO_WRITE);
> +	byte_1 = *(uint8_t *)(vcpu->run->mmio.data);
> +
> +	td_vcpu_run(vcpu);
> +	TDX_TEST_CHECK_GUEST_FAILURE(vcpu);
> +	TDX_TEST_ASSERT_MMIO(vcpu, TDX_MMIO_TEST_ADDR, 2, TDG_VP_VMCALL_VE_REQUEST_MMIO_WRITE);
> +	byte_2 = *(uint16_t *)(vcpu->run->mmio.data);
> +
> +	td_vcpu_run(vcpu);
> +	TDX_TEST_CHECK_GUEST_FAILURE(vcpu);
> +	TDX_TEST_ASSERT_MMIO(vcpu, TDX_MMIO_TEST_ADDR, 4, TDG_VP_VMCALL_VE_REQUEST_MMIO_WRITE);
> +	byte_4 = *(uint32_t *)(vcpu->run->mmio.data);
> +
> +	td_vcpu_run(vcpu);
> +	TDX_TEST_CHECK_GUEST_FAILURE(vcpu);
> +	TDX_TEST_ASSERT_MMIO(vcpu, TDX_MMIO_TEST_ADDR, 8, TDG_VP_VMCALL_VE_REQUEST_MMIO_WRITE);
> +	byte_8 = *(uint64_t *)(vcpu->run->mmio.data);
> +
> +	TEST_ASSERT_EQ(byte_1, 0x12);
> +	TEST_ASSERT_EQ(byte_2, 0x1234);
> +	TEST_ASSERT_EQ(byte_4, 0x12345678);
> +	TEST_ASSERT_EQ(byte_8, 0x1234567890ABCDEF);
> +
> +	td_vcpu_run(vcpu);
> +	TEST_ASSERT_EQ(vcpu->run->exit_reason, KVM_EXIT_SYSTEM_EVENT);
> +	TEST_ASSERT_EQ(vcpu->run->system_event.data[1], TDG_VP_VMCALL_INVALID_OPERAND);
Is it possible that this event is caused by an failure of the last 8 byte write?
i.e. though MMIO exit to host with correct value 0x1234567890ABCDEF, but guest
sees ret as TDG_VP_VMCALL_INVALID_OPERAND.

And if, coincidently, guest gets a ret=0 in the next across page boundary write,
the selftest will show "PASSED", which is not right.


> +	td_vcpu_run(vcpu);
> +	TDX_TEST_ASSERT_SUCCESS(vcpu);
> +
> +	kvm_vm_free(vm);
> +	printf("\t ... PASSED\n");
> +}
> +
>  int main(int argc, char **argv)
>  {
>  	setbuf(stdout, NULL);
> @@ -905,6 +989,7 @@ int main(int argc, char **argv)
>  	run_in_new_process(&verify_guest_msr_reads);
>  	run_in_new_process(&verify_guest_hlt);
>  	run_in_new_process(&verify_mmio_reads);
> +	run_in_new_process(&verify_mmio_writes);
>  
>  	return 0;
>  }
> -- 
> 2.43.0.472.g3155946c3a-goog
> 
>