linux-kernel - Re: [PATCH V5 4/4] kvm: add a check if pfn is from NVDIMM pmem.

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Message-ID: <20181019123348.04ee7dd8@gnomeregan.cam.corp.google.com>
Date:   Fri, 19 Oct 2018 12:33:48 -0400
From:   Barret Rhoden <brho@...gle.com>
To:     David Hildenbrand <david@...hat.com>,
        Dan Williams <dan.j.williams@...el.com>
Cc:     KVM list <kvm@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-nvdimm <linux-nvdimm@...ts.01.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Dave Jiang <dave.jiang@...el.com>,
        "Zhang, Yu C" <yu.c.zhang@...el.com>,
        Pankaj Gupta <pagupta@...hat.com>, Jan Kara <jack@...e.cz>,
        Christoph Hellwig <hch@....de>, Linux MM <linux-mm@...ck.org>,
        rkrcmar@...hat.com,
        Jérôme Glisse <jglisse@...hat.com>,
        "Zhang, Yi Z" <yi.z.zhang@...el.com>
Subject: Re: [PATCH V5 4/4] kvm: add a check if pfn is from NVDIMM pmem.

On 2018-09-21 at 21:29 David Hildenbrand <david@...hat.com> wrote:
> On 21/09/2018 20:17, Dan Williams wrote:
> > On Fri, Sep 21, 2018 at 7:24 AM David Hildenbrand <david@...hat.com> wrote:
> > [..]  
> >>> Remove the PageReserved flag sounds more reasonable.
> >>> And Could we still have a flag to identify it is a device private memory, or
> >>> where these pages coming from?  
> >>
> >> We could use a page type for that or what you proposed. (as I said, we
> >> might have to change hibernation code to skip the pages once we drop the
> >> reserved flag).  
> > 
> > I think it would be reasonable to reject all ZONE_DEVICE pages in
> > saveable_page().
> >   
> 
> Indeed, that sounds like the easiest solution - guess that answer was
> too easy for me to figure out :) .
> 

Just to follow-up, is the plan to clear PageReserved for nvdimm pages
instead of the approach taken in this patch set?  Or should we special
case nvdimm/dax pages in kvm_is_reserved_pfn()?

Thanks,

Barret