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Date:   Mon, 9 Apr 2018 11:26:01 +0800
From:   Stefan Hajnoczi <stefanha@gmail.com>
To:     Pankaj Gupta <pagupta@redhat.com>
Cc:     David Hildenbrand <david@redhat.com>, kwolf@redhat.com,
        haozhong zhang <haozhong.zhang@intel.com>, jack@suse.cz,
        xiaoguangrong eric <xiaoguangrong.eric@gmail.com>,
        kvm@vger.kernel.org, riel@surriel.com, linux-nvdimm@ml01.01.org,
        mst@redhat.com, ross zwisler <ross.zwisler@intel.com>,
        linux-kernel@vger.kernel.org, qemu-devel@nongnu.org,
        hch@infradead.org, pbonzini@redhat.com, stefanha@redhat.com,
        niteshnarayanlal@hotmail.com, marcel@redhat.com,
        imammedo@redhat.com, dan j williams <dan.j.williams@intel.com>,
        nilal@redhat.com
Subject: Re: [Qemu-devel] [RFC] qemu: Add virtio pmem device
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On Thu, Apr 05, 2018 at 08:09:26AM -0400, Pankaj Gupta wrote:
> > Will this raw file already have the "disk information header" (no idea
> > how that stuff is called) encoded? Are there any plans/possible ways to
> >=20
> > a) automatically create the headers? (if that's even possible)
>=20
> Its raw. Right now we are just supporting raw format. =20
>=20
> As this is direct mapping of memory into guest address space, I don't
> think we can have an abstraction of headers for block specific features.
> Or may be we can get opinion of others(Qemu block people) it is at all po=
ssible?

memdev and the block layer are completely separate.  The block layer
isn't designed for memory-mapped access.

I think it makes sense to use memdev here.  If the user wants a block
device, they should use an emulated block device, not virtio-pmem,
because buffering is necessary anyway when an image file format is used.

Stefan

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