On Wed, Jan 26, 2022 at 02:55:10PM +0100, David Hildenbrand wrote: > On 26.01.22 14:38, Matthew Wilcox wrote: > > On Wed, Jan 26, 2022 at 11:16:42AM +0100, David Hildenbrand wrote: > >> A while ago I talked with Peter about an extended uffd (here: WP) > >> mechanism that would work on fds instead of the process address space. > > > > As far as I can tell, uffd is a grotesque hack that exists to work around > > the poor choice to use anonymous memory instead of file-backed memory > > in kvm. Every time I see somebody mention it, I feel pain. > > > > I might be missing something important, because KVM can deal with > file-back memory just fine and uffd is used heavily outside of hypervisors. > > I'd love to learn how to handle what ordinary uffd (handle > missing/unpopulated pages) and uffd-wp (handle write access to pages) > can do with files instead. Because if something like that already > exists, it would be precisely what I am talking about. Every notification that uffd wants already exists as a notification to the underlying filesystem. Something like a uffdfs [1] would be able to do everything that uffd does without adding extra crap all over the MM. [1] acronyms are bad, mmmkay?
