Re: [RFC v2 PATCH 01/13] mm/shmem: Introduce F_SEAL_GUEST

From: David Hildenbrand
Date: Tue Nov 23 2021 - 10:20:14 EST

On 23.11.21 10:06, Paolo Bonzini wrote:
> On 11/19/21 16:39, David Hildenbrand wrote:
>>> 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 :)


David / dhildenb