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

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Message-ID: <20200107190522.GA16987@linux.intel.com>
Date:   Tue, 7 Jan 2020 11:05:22 -0800
From:   Sean Christopherson <sean.j.christopherson@...el.com>
To:     Barret Rhoden <brho@...gle.com>
Cc:     Liran Alon <liran.alon@...cle.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Dan Williams <dan.j.williams@...el.com>,
        David Hildenbrand <david@...hat.com>,
        Dave Jiang <dave.jiang@...el.com>,
        Alexander Duyck <alexander.h.duyck@...ux.intel.com>,
        linux-nvdimm@...ts.01.org, x86@...nel.org, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org, jason.zeng@...el.com
Subject: Re: [PATCH v5 2/2] kvm: Use huge pages for DAX-backed files

On Mon, Dec 16, 2019 at 11:05:26AM -0500, Barret Rhoden wrote:
> On 12/13/19 12:19 PM, Sean Christopherson wrote:
> >Teaching thp_adjust() how to handle 1GB wouldn't be a bad thing.  It's
> >unlikely THP itself will support 1GB pages any time soon, but having the
> >logic there wouldn't hurt anything.
> >
> 
> Cool.  This was my main concern - I didn't want to break THP.
> 
> I'll rework the series based on all of your comments.

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.