Re: [RFC v2 PATCH 04/13] KVM: Add fd-based memslot data structure and utils

[Chao Peng]

On Tue, Nov 23, 2021 at 09:41:34AM +0100, Paolo Bonzini wrote:
> On 11/19/21 14:47, Chao Peng wrote:
> > For fd-based memslot store the file references for shared fd and the
> > private fd (if any) in the memslot structure. Since there is no 'hva'
> > concept we cannot call hva_to_pfn() to get a pfn, instead kvm_memfd_ops
> > is added to get_pfn/put_pfn from the memory backing stores that provide
> > these fds.
> > 
> > Signed-off-by: Yu Zhang<yu.c.zhang@xxxxxxxxxxxxxxx>
> > Signed-off-by: Chao Peng<chao.p.peng@xxxxxxxxxxxxxxx>
> > ---
> 
> What about kvm_read/write_guest? 

Hmm, that would be another area KVM needs to change. Not totally
undoable.

> Maybe the proposal which kept
> userspace_addr for the shared fd is more doable (it would be great to
> ultimately remove the mandatory userspace mapping for the shared fd, but I
> think KVM is not quite ready for that).

Agree for short term keeping shared part unchanged would be making work
easy:) Let me try that to see if any blocker.

> 
> Paolo