Re: [PATCH] vfio/pci: take mmap write lock for io_remap_pfn_range

[Jason Gunthorpe]

On Mon, May 08, 2023 at 02:57:15PM -0600, Alex Williamson wrote:

> We already try to set the flags in advance, but there are some
> architectural flags like VM_PAT that make that tricky.  Cedric has been
> looking at inserting individual pages with vmf_insert_pfn(), but that
> incurs a lot more faults and therefore latency vs remapping the entire
> vma on fault.  I'm not convinced that we shouldn't just attempt to
> remove the fault handler entirely, but I haven't tried it yet to know
> what gotchas are down that path.  Thanks,

I thought we did it like this because there were races otherwise with
PTE insertion and zapping? I don't remember well anymore.

I vaugely remember the address_space conversion might help remove the
fault handler?

Jason