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

[Michael Roth]

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