linux-kernel - Re: [PATCH v8 08/30] KVM: selftests: TDX: Update load_td_memory_region() for VM memory backed by guest memfd

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Message-ID: <4b938a0a-a4ef-42c9-aef5-c931f2ad8aa0@linux.intel.com>
Date: Wed, 13 Aug 2025 17:23:17 +0800
From: Binbin Wu <binbin.wu@...ux.intel.com>
To: Sean Christopherson <seanjc@...gle.com>, 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>, 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 08/30] KVM: selftests: TDX: Update
 load_td_memory_region() for VM memory backed by guest memfd

On 8/12/2025 4:31 AM, Sean Christopherson wrote:
> On Thu, Aug 07, 2025, Sagi Shahar wrote:
[...]
>> +
>>   /*
>>    * TD creation/setup/finalization
>>    */
>> @@ -459,28 +474,35 @@ static void load_td_memory_region(struct kvm_vm *vm,
>>   	if (!sparsebit_any_set(pages))
>>   		return;
>>   
>> +	if (region->region.guest_memfd != -1)
>> +		register_encrypted_memory_region(vm, region);
>> +
>>   	sparsebit_for_each_set_range(pages, i, j) {
>>   		const uint64_t size_to_load = (j - i + 1) * vm->page_size;
>>   		const uint64_t offset =
>>   			(i - lowest_page_in_region) * vm->page_size;
>>   		const uint64_t hva = hva_base + offset;
>>   		const uint64_t gpa = gpa_base + offset;
>> -		void *source_addr;
>> +		void *source_addr = (void *)hva;
>>   
>>   		/*
>>   		 * KVM_TDX_INIT_MEM_REGION ioctl cannot encrypt memory in place.
>>   		 * Make a copy if there's only one backing memory source.
>>   		 */
>> -		source_addr = mmap(NULL, size_to_load, PROT_READ | PROT_WRITE,
>> -				   MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
>> -		TEST_ASSERT(source_addr,
>> -			    "Could not allocate memory for loading memory region");
>> -
>> -		memcpy(source_addr, (void *)hva, size_to_load);
>> +		if (region->region.guest_memfd == -1) {
> Oh, here's the "if".

Is it still possible for "region->region.guest_memfd == -1" case?
KVM_TDX_INIT_MEM_REGION can only work with guest memfd, right?

>
>> +			source_addr = mmap(NULL, size_to_load, PROT_READ | PROT_WRITE,
>> +					   MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
>> +			TEST_ASSERT(source_addr,
>> +				    "Could not allocate memory for loading memory region");
>> +
>> +			memcpy(source_addr, (void *)hva, size_to_load);
>> +			memset((void *)hva, 0, size_to_load);
>> +		}
>>   
>>   		tdx_init_mem_region(vm, source_addr, gpa, size_to_load);
>>   
>> -		munmap(source_addr, size_to_load);
>> +		if (region->region.guest_memfd == -1)
>> +			munmap(source_addr, size_to_load);
>>   	}
>>   }
>>   
>> -- 
>> 2.51.0.rc0.155.g4a0f42376b-goog
>>