Re: [PATCH v4 08/12] hostmem: Support fully shared guest memfd to back a VM

[Peter Xu <peterx@redhat.com>]

On Fri, Aug 14, 2026 at 04:27:31PM +0100, Daniel P. Berrangé wrote:
> Yes, if we think we can make QEMU "do the right thing" internally
> that makes a separate object much less desirable. That would
> be saying that we have a tri-state,  guest_memfd=auto|on|off,
> and such tri-state's would not invite a separate sub-class
> design. The need for "auto" rather forces the approach you have
> in this patch.

Just to mention, one option here is we don't introduce "auto" at all,
guest-memfd=on could explicitly mean the init full shared mode too.

IOW, when used in a CoCo context, memfd objects will be normally silently
created with guest-memfds, like what we used to silently create guest-memfd
2nd layer without any cmdlines, but this time when in-place convertable
it'll be the solo backend.  User doesn't even need to know.

Then, when guest-memfd=on is specified in such a CoCo context, it should be
able to make this specific chunk of memory "init-shared", while the rest
could still be in-place convertable.  This may make the cmdline slightly
more flexible to allow init shared also in CoCo. But I confess I don't know
if that would be useful ultimately, and I didn't think all things through.

Thanks,

-- 
Peter Xu