Re: [RFC PATCH 12/21] KVM: IOMMUFD: MEMFD: Map private pages

Jason Gunthorpe
2024-09-24T12:07:41Z

On Mon, Sep 23, 2024 at 11:52:19PM +0000, Tian, Kevin wrote:
> > IMHO we should try to do as best we can here, and the ideal interface
> > would be a notifier to switch the shared/private pages in some portion
> > of the guestmemfd. With the idea that iommufd could perhaps do it
> > atomically.
>
> yes atomic replacement is necessary here, as there might be in-fly
> DMAs to pages adjacent to the one being converted in the same
> 1G hunk. Unmap/remap could potentially break it.

Yeah.. This integration is going to be much more complicated than I
originally thought about. It will need the generic pt stuff as the
hitless page table manipulations we are contemplating here are pretty
complex.

Jason