Re: [PATCH 0/2] KVM: do not assume PTE is writable after follow_pfn

[Jason Gunthorpe]

On Fri, Feb 05, 2021 at 01:14:11PM -0500, Peter Xu wrote:

> But I do have a question on why dax as the only user needs to pass in the
> notifier to follow_pte() for initialization.

Not sure either, why does DAX opencode something very much like
page_mkclean() with dax_entry_mkclean()?

Also it looks like DAX uses the wrong notifier, it calls
MMU_NOTIFY_CLEAR but page_mkclean_one() uses
MMU_NOTIFY_PROTECTION_PAGE for the same PTE modification sequence??

page_mkclean() has some technique to make the notifier have the right
size without becoming entangled in the PTL locks..

Jason