linux-kernel - Re: [Qemu-devel] [PATCH v2 0/2] kvm "fake DAX" device

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Date:   Sat, 13 Oct 2018 12:29:12 -0400 (EDT)
From:   Pankaj Gupta <pagupta@...hat.com>
To:     Dan Williams <dan.j.williams@...el.com>
Cc:     Kevin Wolf <kwolf@...hat.com>, Jan Kara <jack@...e.cz>,
        Xiao Guangrong <xiaoguangrong.eric@...il.com>,
        KVM list <kvm@...r.kernel.org>,
        Rik van Riel <riel@...riel.com>,
        linux-nvdimm <linux-nvdimm@...1.01.org>,
        David Hildenbrand <david@...hat.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Dave Jiang <dave.jiang@...el.com>,
        Qemu Developers <qemu-devel@...gnu.org>,
        Christoph Hellwig <hch@...radead.org>,
        Vishal L Verma <vishal.l.verma@...el.com>,
        Igor Mammedov <imammedo@...hat.com>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Stefan Hajnoczi <stefanha@...hat.com>, zwisler@...nel.org,
        lcapitulino@...hat.com, Paolo Bonzini <pbonzini@...hat.com>,
        Nitesh Narayan Lal <nilal@...hat.com>
Subject: Re: [Qemu-devel] [PATCH v2 0/2] kvm "fake DAX" device


> >
> >  This patch series has implementation for "fake DAX".
> >  "fake DAX" is fake persistent memory(nvdimm) in guest
> >  which allows to bypass the guest page cache. This also
> >  implements a VIRTIO based asynchronous flush mechanism.
> 
> Can we stop calling this 'fake DAX', because it isn't 'DAX' and it's
> starting to confuse people. This enabling is effectively a
> host-page-cache-passthrough mechanism not DAX. Let's call the whole
> approach virtio-pmem, and leave DAX out of the name to hopefully
> prevent people from wondering why some DAX features are disabled with
> this driver. For example MAP_SYNC is not compatible with this
> approach.

Sure. I got your point. I will use "virtio-pmem" in future.  

> 
> Additional enabling is need to disable MAP_SYNC in the presence of a
> virtio-pmem device. See the rough proposal here:
> 
>     https://lkml.org/lkml/2018/4/25/756

Yes, I will handle disabling of MAP_SYNC for this use-case.


Thanks,
Pankaj