linux-kernel - Re: [RFC PATCH v5 07/29] KVM: selftests: TDX: Update load_td_memory_region for VM memory backed by guest memfd

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Date: Thu, 22 Feb 2024 17:19:32 +0800
From: Yan Zhao <yan.y.zhao@...el.com>
To: Sagi Shahar <sagis@...gle.com>
CC: <linux-kselftest@...r.kernel.org>, Ackerley Tng <ackerleytng@...gle.com>,
	Ryan Afranji <afranji@...gle.com>, Erdem Aktas <erdemaktas@...gle.com>,
	"Isaku Yamahata" <isaku.yamahata@...el.com>, Sean Christopherson
	<seanjc@...gle.com>, Paolo Bonzini <pbonzini@...hat.com>, Shuah Khan
	<shuah@...nel.org>, "Peter Gonda" <pgonda@...gle.com>, Haibo Xu
	<haibo1.xu@...el.com>, Chao Peng <chao.p.peng@...ux.intel.com>, Vishal
 Annapurve <vannapurve@...gle.com>, Roger Wang <runanwang@...gle.com>, Vipin
 Sharma <vipinsh@...gle.com>, <jmattson@...gle.com>, <dmatlack@...gle.com>,
	<linux-kernel@...r.kernel.org>, <kvm@...r.kernel.org>, <linux-mm@...ck.org>
Subject: Re: [RFC PATCH v5 07/29] KVM: selftests: TDX: Update
 load_td_memory_region for VM memory backed by guest memfd

On Tue, Dec 12, 2023 at 12:46:22PM -0800, Sagi Shahar wrote:
> From: Ackerley Tng <ackerleytng@...gle.com>
> 
> If guest memory is backed by restricted memfd
> 
> + UPM is being used, hence encrypted memory region has to be
>   registered
> + Can avoid making a copy of guest memory before getting TDX to
>   initialize the memory region
> 
> Signed-off-by: Ackerley Tng <ackerleytng@...gle.com>
> Signed-off-by: Ryan Afranji <afranji@...gle.com>
> Signed-off-by: Sagi Shahar <sagis@...gle.com>
> ---
>  .../selftests/kvm/lib/x86_64/tdx/tdx_util.c   | 41 +++++++++++++++----
>  1 file changed, 32 insertions(+), 9 deletions(-)
> 
> diff --git a/tools/testing/selftests/kvm/lib/x86_64/tdx/tdx_util.c b/tools/testing/selftests/kvm/lib/x86_64/tdx/tdx_util.c
> index 6b995c3f6153..063ff486fb86 100644
> --- a/tools/testing/selftests/kvm/lib/x86_64/tdx/tdx_util.c
> +++ b/tools/testing/selftests/kvm/lib/x86_64/tdx/tdx_util.c
> @@ -192,6 +192,21 @@ static void tdx_td_finalizemr(struct kvm_vm *vm)
>  	tdx_ioctl(vm->fd, KVM_TDX_FINALIZE_VM, 0, NULL);
>  }
>  
> +/*
> + * Other ioctls
> + */
> +
> +/**
> + * Register a memory region that may contain encrypted data in KVM.
> + */
> +static void register_encrypted_memory_region(
> +	struct kvm_vm *vm, struct userspace_mem_region *region)
> +{
> +	vm_set_memory_attributes(vm, region->region.guest_phys_addr,
> +				 region->region.memory_size,
> +				 KVM_MEMORY_ATTRIBUTE_PRIVATE);
> +}
> +
>  /*
>   * TD creation/setup/finalization
>   */
> @@ -376,30 +391,38 @@ 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,
>  		 * hence we have to 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) {
> +			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);
>  	}

For memslot 0, 1, 2, when guest_memfd != -1,
is it possible to also munmap(mmap_start, mmap_size) after finish loading?

>  }
>  
> -- 
> 2.43.0.472.g3155946c3a-goog
> 
>