Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Date:   Tue, 7 Jan 2020 17:20:15 -0800
From:   Sean Christopherson <sean.j.christopherson@intel.com>
To:     Barret Rhoden <brho@google.com>
Cc:     Liran Alon <liran.alon@oracle.com>,
        Paolo Bonzini <pbonzini@redhat.com>,
        Dan Williams <dan.j.williams@intel.com>,
        David Hildenbrand <david@redhat.com>,
        Dave Jiang <dave.jiang@intel.com>,
        Alexander Duyck <alexander.h.duyck@linux.intel.com>,
        linux-nvdimm@lists.01.org, x86@kernel.org, kvm@vger.kernel.org,
        linux-kernel@vger.kernel.org, jason.zeng@intel.com
Subject: Re: [PATCH v5 2/2] kvm: Use huge pages for DAX-backed files
Message-ID: <20200108012014.GF16987@linux.intel.com>
References: <20191212182238.46535-1-brho@google.com>
 <20191212182238.46535-3-brho@google.com>
 <06108004-1720-41EB-BCAB-BFA8FEBF4772@oracle.com>
 <ED482280-CB47-4AB6-9E7E-EEE7848E0F8B@oracle.com>
 <f8e948ff-6a2a-a6d6-9d8e-92b93003354a@google.com>
 <65FB6CC1-3AD2-4D6F-9481-500BD7037203@oracle.com>
 <20191213171950.GA31552@linux.intel.com>
 <e012696f-f13e-5af1-2b14-084607d69bfa@google.com>
 <20200107190522.GA16987@linux.intel.com>
 <08a36944-ad5a-ca49-99b3-d3908ce0658b@google.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <08a36944-ad5a-ca49-99b3-d3908ce0658b@google.com>
User-Agent: Mutt/1.5.24 (2015-08-30)
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

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
PageTransCompoundMap().

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

Thanks!