linux-kernel - Re: [PATCH v8 21/30] KVM: selftests: TDX: Verify the behavior when host consumes a TD private memory

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Message-ID: <aJpUDS4PSgLK8A16@google.com>
Date: Mon, 11 Aug 2025 13:35:25 -0700
From: Sean Christopherson <seanjc@...gle.com>
To: Sagi Shahar <sagis@...gle.com>
Cc: linux-kselftest@...r.kernel.org, Paolo Bonzini <pbonzini@...hat.com>, 
	Shuah Khan <shuah@...nel.org>, Ackerley Tng <ackerleytng@...gle.com>, 
	Ryan Afranji <afranji@...gle.com>, Andrew Jones <ajones@...tanamicro.com>, 
	Isaku Yamahata <isaku.yamahata@...el.com>, Erdem Aktas <erdemaktas@...gle.com>, 
	Rick Edgecombe <rick.p.edgecombe@...el.com>, Roger Wang <runanwang@...gle.com>, 
	Binbin Wu <binbin.wu@...ux.intel.com>, Oliver Upton <oliver.upton@...ux.dev>, 
	"Pratik R. Sampat" <pratikrajesh.sampat@....com>, Reinette Chatre <reinette.chatre@...el.com>, 
	Ira Weiny <ira.weiny@...el.com>, linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Subject: Re: [PATCH v8 21/30] KVM: selftests: TDX: Verify the behavior when
 host consumes a TD private memory

On Thu, Aug 07, 2025, Sagi Shahar wrote:
> +void verify_host_reading_private_mem(void)
> +{
> +	uint64_t second_host_read;
> +	uint64_t first_host_read;
> +	struct kvm_vcpu *vcpu;
> +	vm_vaddr_t test_page;
> +	uint64_t *host_virt;
> +	struct kvm_vm *vm;
> +
> +	vm = td_create();
> +	td_initialize(vm, VM_MEM_SRC_ANONYMOUS, 0);
> +	vcpu = td_vcpu_add(vm, 0, guest_host_read_priv_mem);
> +
> +	test_page = vm_vaddr_alloc_page(vm);
> +	TEST_ASSERT(test_page < BIT_ULL(32),
> +		    "Test address should fit in 32 bits so it can be sent to the guest");
> +
> +	host_virt = addr_gva2hva(vm, test_page);
> +	TEST_ASSERT(host_virt,
> +		    "Guest address not found in guest memory regions\n");
> +
> +	tdx_test_host_read_private_mem_addr = test_page;
> +	sync_global_to_guest(vm, tdx_test_host_read_private_mem_addr);
> +
> +	td_finalize(vm);
> +
> +	printf("Verifying host's behavior when reading TD private memory:\n");
> +
> +	tdx_run(vcpu);
> +	tdx_test_assert_io(vcpu, TDX_HOST_READ_PRIVATE_MEM_PORT_TEST,
> +			   4, PORT_WRITE);
> +	printf("\t ... Guest's variable contains 0xABCD\n");

Don't use bare printf() for what is effectively debug info.
> +
> +	/* Host reads guest's variable. */
> +	first_host_read = *host_virt;
> +	printf("\t ... Host's read attempt value: %lu\n", first_host_read);
> +
> +	/* Guest updates variable and host rereads it. */
> +	tdx_run(vcpu);
> +	printf("\t ... Guest's variable updated to 0xFEDC\n");
> +
> +	second_host_read = *host_virt;
> +	printf("\t ... Host's second read attempt value: %lu\n",
> +	       second_host_read);
> +
> +	TEST_ASSERT(first_host_read == second_host_read,
> +		    "Host did not read a fixed pattern\n");
> +
> +	printf("\t ... Fixed pattern was returned to the host\n");
> +
> +	kvm_vm_free(vm);
> +	printf("\t ... PASSED\n");
> +}
> +
>  int main(int argc, char **argv)
>  {
>  	ksft_print_header();
> @@ -966,7 +1045,7 @@ 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(13);
> +	ksft_set_plan(14);
>  	ksft_test_result(!run_in_new_process(&verify_td_lifecycle),
>  			 "verify_td_lifecycle\n");

This _really_ feels like it wants to be a first mover for using fixtures and
test suites: https://lore.kernel.org/all/ZjUwqEXPA5QVItyX@google.com

>  	ksft_test_result(!run_in_new_process(&verify_report_fatal_error),
> @@ -993,6 +1072,8 @@ int main(int argc, char **argv)
>  			 "verify_mmio_writes\n");
>  	ksft_test_result(!run_in_new_process(&verify_td_cpuid_tdcall),
>  			 "verify_td_cpuid_tdcall\n");
> +	ksft_test_result(!run_in_new_process(&verify_host_reading_private_mem),
> +			 "verify_host_reading_private_mem\n");
>  
>  	ksft_finished();
>  	return 0;
> -- 
> 2.51.0.rc0.155.g4a0f42376b-goog
>