Re: [RFC 02/16] KVM: selftests: add hooks for managing encrypted guest memory

On Mon, Oct 18, 2021 at 08:00:00AM -0700, Mingwei Zhang wrote:

...

+void vm_set_memory_encryption(struct kvm_vm *vm, bool enc_by_default, bool has_enc_bit,

•                         uint8_t enc_bit)
  

+{

•   vm->memcrypt.enabled = true;
  

•   vm->memcrypt.enc_by_default = enc_by_default;
  

•   vm->memcrypt.has_enc_bit = has_enc_bit;
  

•   vm->memcrypt.enc_bit = enc_bit;
  

+}

+struct sparsebit * +vm_get_encrypted_phy_pages(struct kvm_vm *vm, int slot, vm_paddr_t *gpa_start,

•                      uint64_t *size)
  

+{

•   struct userspace_mem_region *region;
  

•   struct sparsebit *encrypted_phy_pages;
  

•   if (!vm->memcrypt.enabled)
  

•           return NULL;
  

•   region = memslot2region(vm, slot);
  

•   if (!region)
  

•           return NULL;
  

•   encrypted_phy_pages = sparsebit_alloc();
  

•   sparsebit_copy(encrypted_phy_pages, region->encrypted_phy_pages);
  

Do we have to make a copy for the sparsebit? Why not just return the pointer? By looking at your subsequent patches, I find that this data structure seems to be just read-only?

Yes, it's only intended to be used for read access. But I'll if I can enforce that without the need to use a copy.

-Mingwei