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Date: Fri, 1 Mar 2024 20:02:43 +0800
From: Yan Zhao <yan.y.zhao@intel.com>
To: Sagi Shahar <sagis@google.com>
CC: <linux-kselftest@vger.kernel.org>, Ackerley Tng <ackerleytng@google.com>,
	Ryan Afranji <afranji@google.com>, Erdem Aktas <erdemaktas@google.com>, Isaku
 Yamahata <isaku.yamahata@intel.com>, Sean Christopherson <seanjc@google.com>,
	Paolo Bonzini <pbonzini@redhat.com>, Shuah Khan <shuah@kernel.org>, Peter
 Gonda <pgonda@google.com>, Haibo Xu <haibo1.xu@intel.com>, Chao Peng
	<chao.p.peng@linux.intel.com>, "Vishal Annapurve" <vannapurve@google.com>,
	Roger Wang <runanwang@google.com>, "Vipin Sharma" <vipinsh@google.com>,
	<jmattson@google.com>, <dmatlack@google.com>, <linux-kernel@vger.kernel.org>,
	<kvm@vger.kernel.org>, <linux-mm@kvack.org>
Subject: Re: [RFC PATCH v5 23/29] KVM: selftests: TDX: Add shared memory test
Message-ID: <ZeHD44xpj75ixcUr@yzhao56-desk.sh.intel.com>
Reply-To: Yan Zhao <yan.y.zhao@intel.com>
References: <20231212204647.2170650-1-sagis@google.com>
 <20231212204647.2170650-24-sagis@google.com>
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> +void guest_shared_mem(void)
> +{
> +	uint32_t *test_mem_shared_gva =
> +		(uint32_t *)TDX_SHARED_MEM_TEST_SHARED_GVA;
> +
> +	uint64_t placeholder;
> +	uint64_t ret;
> +
> +	/* Map gpa as shared */
> +	ret = tdg_vp_vmcall_map_gpa(test_mem_shared_gpa, PAGE_SIZE,
> +				    &placeholder);
> +	if (ret)
> +		tdx_test_fatal_with_data(ret, __LINE__);
> +
> +	*test_mem_shared_gva = TDX_SHARED_MEM_TEST_GUEST_WRITE_VALUE;
> +
> +	/* Exit so host can read shared value */
> +	ret = tdg_vp_vmcall_instruction_io(TDX_SHARED_MEM_TEST_INFO_PORT, 4,
> +					   TDG_VP_VMCALL_INSTRUCTION_IO_WRITE,
> +					   &placeholder);
> +	if (ret)
> +		tdx_test_fatal_with_data(ret, __LINE__);
> +
> +	/* Read value written by host and send it back out for verification */
> +	ret = tdg_vp_vmcall_instruction_io(TDX_SHARED_MEM_TEST_INFO_PORT, 4,
> +					   TDG_VP_VMCALL_INSTRUCTION_IO_WRITE,
> +					   (uint64_t *)test_mem_shared_gva);
> +	if (ret)
> +		tdx_test_fatal_with_data(ret, __LINE__);
> +}
> +
> +int verify_shared_mem(void)
> +{
> +	struct kvm_vm *vm;
> +	struct kvm_vcpu *vcpu;
> +
> +	vm_vaddr_t test_mem_private_gva;
> +	uint32_t *test_mem_hva;
> +
> +	vm = td_create();
> +	td_initialize(vm, VM_MEM_SRC_ANONYMOUS, 0);
> +	vcpu = td_vcpu_add(vm, 0, guest_shared_mem);
> +
> +	/*
> +	 * Set up shared memory page for testing by first allocating as private
> +	 * and then mapping the same GPA again as shared. This way, the TD does
> +	 * not have to remap its page tables at runtime.
> +	 */
> +	test_mem_private_gva = vm_vaddr_alloc(vm, vm->page_size,
> +					      TDX_SHARED_MEM_TEST_PRIVATE_GVA);
> +	TEST_ASSERT_EQ(test_mem_private_gva, TDX_SHARED_MEM_TEST_PRIVATE_GVA);
> +
> +	test_mem_hva = addr_gva2hva(vm, test_mem_private_gva);
> +	TEST_ASSERT(test_mem_hva != NULL,
> +		    "Guest address not found in guest memory regions\n");
> +
> +	test_mem_private_gpa = addr_gva2gpa(vm, test_mem_private_gva);
> +	virt_pg_map_shared(vm, TDX_SHARED_MEM_TEST_SHARED_GVA,
> +			   test_mem_private_gpa);
> +
> +	test_mem_shared_gpa = test_mem_private_gpa | BIT_ULL(vm->pa_bits - 1);
> +	sync_global_to_guest(vm, test_mem_private_gpa);
> +	sync_global_to_guest(vm, test_mem_shared_gpa);
> +
> +	td_finalize(vm);
> +
> +	printf("Verifying shared memory accesses for TDX\n");
> +
> +	/* Begin guest execution; guest writes to shared memory. */
> +	printf("\t ... Starting guest execution\n");
> +
> +	/* Handle map gpa as shared */
> +	td_vcpu_run(vcpu);
> +	TDX_TEST_CHECK_GUEST_FAILURE(vcpu);
The first VMExit should be caused by tdvmcall map gpa, so it's
impossible to be guest failure.

Move this line TDX_TEST_CHECK_GUEST_FAILURE(vcpu) to after the next td_vcpu_run()
is better.
> +
> +	td_vcpu_run(vcpu);
> +	TDX_TEST_ASSERT_IO(vcpu, TDX_SHARED_MEM_TEST_INFO_PORT, 4,
> +			   TDG_VP_VMCALL_INSTRUCTION_IO_WRITE);
> +	TEST_ASSERT_EQ(*test_mem_hva, TDX_SHARED_MEM_TEST_GUEST_WRITE_VALUE);
> +
> +	*test_mem_hva = TDX_SHARED_MEM_TEST_HOST_WRITE_VALUE;
> +	td_vcpu_run(vcpu);
> +	TDX_TEST_ASSERT_IO(vcpu, TDX_SHARED_MEM_TEST_INFO_PORT, 4,
> +			   TDG_VP_VMCALL_INSTRUCTION_IO_WRITE);
> +	TEST_ASSERT_EQ(
> +		*(uint32_t *)((void *)vcpu->run + vcpu->run->io.data_offset),
> +		TDX_SHARED_MEM_TEST_HOST_WRITE_VALUE);
> +
> +	printf("\t ... PASSED\n");
> +
> +	kvm_vm_free(vm);
> +
> +	return 0;
> +}