Re: [PATCH v5 2/2] kvm: Use huge pages for DAX-backed files

From: Sean Christopherson
Date: Tue Jan 07 2020 - 20:20:17 EST

On Tue, Jan 07, 2020 at 02:19:06PM -0500, Barret Rhoden wrote:
> On 1/7/20 2:05 PM, Sean Christopherson wrote:
> >Hopefully you haven't put too much effort into the rework, because I want
> >to commandeer the proposed changes and use them as the basis for a more
> >aggressive overhaul of KVM's hugepage handling. Ironically, there's a bug
> >in KVM's THP handling that I _think_ can be avoided by using the DAX
> >approach of walking the host PTEs.
> >
> >I'm in the process of testing, hopefully I'll get a series sent out later
> >today. If not, I should at least be able to provide an update.
> Nice timing. I was just about to get back to this, so I haven't put any
> time in yet. =)
> Please CC me, and I'll try your patches out on my end.

Will do. Barring last minute hiccups, the code is ready, just need to
finish off a few changelogs. Should get it out early tomorrow.

One question that may help avoid some churn: are huge DAX pages not
tracked as compound pages? The comment from your/this patch is pretty
unequivocal, but I wanted to double check that they will really return
false for PageCompound(), as opposed to only returning false for

* DAX pages do not use compound pages. ...