On 23.11.21 10:06, Paolo Bonzini wrote:

On 11/19/21 16:39, David Hildenbrand wrote:

quoted

quoted

If qmeu can put all the guest memory in a memfd and not map it, then
I'd also like to see that the IOMMU can use this interface too so we
can have VFIO working in this configuration.

In QEMU we usually want to (and must) be able to access guest memory
from user space, with the current design we wouldn't even be able to
temporarily mmap it -- which makes sense for encrypted memory only. The
corner case really is encrypted memory. So I don't think we'll see a
broad use of this feature outside of encrypted VMs in QEMU. I might be
wrong, most probably I am:)

It's not _that_ crazy an idea, but it's going to be some work to teach 
KVM that it has to kmap/kunmap around all memory accesses.

I'm also concerned about userspace access. But you sound like you have a
plan :)

-- 
Thanks,

David / dhildenb