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

[Mingwei Zhang]

On Tue, Oct 26, 2021 at 8:48 AM Mingwei Zhang <mizhang@xxxxxxxxxx> wrote:
>
> On Wed, Oct 20, 2021 at 8:46 PM Michael Roth <michael.roth@xxxxxxx> wrote:
> >
> > 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.
> >
>
> Understood. Thanks for the clarification. Yeah, I think both making a
> copy and returning a const pointer should work. I will leave that to
> you then.
>
> Thanks.
> -Mingwei

Reviewed-by: Mingwei Zhang <mizhang@xxxxxxxxxx>

Thanks.
-Mingwei