On Thu, Aug 07, 2025, Sagi Shahar wrote:
> From: Ackerley Tng <ackerleytng@google.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@google.com>
> Signed-off-by: Sagi Shahar <sagis@google.com>
> ---
> .../selftests/kvm/lib/x86/tdx/tdx_util.c | 38 +++++++++++++++----
> 1 file changed, 30 insertions(+), 8 deletions(-)
>
> diff --git a/tools/testing/selftests/kvm/lib/x86/tdx/tdx_util.c b/tools/testing/selftests/kvm/lib/x86/tdx/tdx_util.c
> index bb074af4a476..e2bf9766dc03 100644
> --- a/tools/testing/selftests/kvm/lib/x86/tdx/tdx_util.c
> +++ b/tools/testing/selftests/kvm/lib/x86/tdx/tdx_util.c
> @@ -324,6 +324,21 @@ static void tdx_td_finalize_mr(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.
> + */
Drop these comments.
> +static void register_encrypted_memory_region(struct kvm_vm *vm,
> + struct userspace_mem_region *region)
This is a comically bad helper. Any person that is at all familiar with KVM's
CoCo support, or that simply reads KVM's documentation, will expect this to
invoke KVM_MEMORY_ENCRYPT_REG_REGION. And this is obviously doing much more than
"registering" an encrypted region. Not to mention this helper doesn't need to
exist; it has _one_ caller, and the code is quite self-explanatory.
> +{
> + vm_set_memory_attributes(vm, region->region.guest_phys_addr,
> + region->region.memory_size,
> + KVM_MEMORY_ATTRIBUTE_PRIVATE);
> +}
> +
> /*
> * 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".
> + 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
>