From mboxrd@z Thu Jan  1 00:00:00 1970
From: Jeff Moyer <jmoyer-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
Subject: Re: [RFC v2 1/2] virtio: add pmem driver
Date: Thu, 26 Apr 2018 08:27:41 -0400
Message-ID: <x49o9i6885e.fsf@segfault.boston.devel.redhat.com>
References: <20180425112415.12327-1-pagupta@redhat.com>
 <20180425112415.12327-2-pagupta@redhat.com>
 <CAPcyv4hvrB08XPTbVK0xT2_1Xmaid=-v3OMxJVDTNwQucsOHLA@mail.gmail.com>
 <CAPcyv4hiowWozV527sQA_e4fdgCYbD6xfG==vepAqu0hxQEQcw@mail.gmail.com>
Mime-Version: 1.0
Content-Type: text/plain; charset="us-ascii"
Content-Transfer-Encoding: 7bit
Return-path: <linux-nvdimm-bounces-hn68Rpc1hR1g9hUCZPvPmw@public.gmane.org>
In-Reply-To: <CAPcyv4hiowWozV527sQA_e4fdgCYbD6xfG==vepAqu0hxQEQcw-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
 (Dan Williams's message of "Wed, 25 Apr 2018 07:43:52 -0700")
List-Unsubscribe: <https://lists.01.org/mailman/options/linux-nvdimm>,
 <mailto:linux-nvdimm-request-hn68Rpc1hR1g9hUCZPvPmw@public.gmane.org?subject=unsubscribe>
List-Archive: <http://lists.01.org/pipermail/linux-nvdimm/>
List-Post: <mailto:linux-nvdimm-hn68Rpc1hR1g9hUCZPvPmw@public.gmane.org>
List-Help: <mailto:linux-nvdimm-request-hn68Rpc1hR1g9hUCZPvPmw@public.gmane.org?subject=help>
List-Subscribe: <https://lists.01.org/mailman/listinfo/linux-nvdimm>,
 <mailto:linux-nvdimm-request-hn68Rpc1hR1g9hUCZPvPmw@public.gmane.org?subject=subscribe>
Errors-To: linux-nvdimm-bounces-hn68Rpc1hR1g9hUCZPvPmw@public.gmane.org
Sender: "Linux-nvdimm" <linux-nvdimm-bounces-hn68Rpc1hR1g9hUCZPvPmw@public.gmane.org>
To: Dan Williams <dan.j.williams-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
Cc: Jan Kara <jack-AlSwsSmVLrQ@public.gmane.org>, KVM list <kvm-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>, David Hildenbrand <david-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>, linux-nvdimm <linux-nvdimm-y27Ovi1pjclAfugRpC6u6w@public.gmane.org>, "Zwisler, Ross" <ross.zwisler-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>, Qemu Developers <qemu-devel-qX2TKyscuCcdnm+yROfE0A@public.gmane.org>, lcapitulino-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org, Linux MM <linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org>, niteshnarayanlal-PkbjNfxxIARBDgjK7y7TUQ@public.gmane.org, "Michael S. Tsirkin" <mst-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>, Christoph Hellwig <hch-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>, Marcel Apfelbaum <marcel-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>, Nitesh Narayan Lal <nilal-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>, Rik van Riel <riel-ebMLmSuQjDVBDgjK7y7TUQ@public.gmane.org>, Stefan Hajnoczi <stefanha-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>, Paolo Bonzini <pbonzini-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>, Kevin Wolf <kwolf-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>, Xiao Guangrong <xiaoguangrong.eric-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>, Linux Kernel Mailing List <linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>, Igor Mammedov <imammedo-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
List-Id: linux-nvdimm@lists.01.org

Dan Williams <dan.j.williams-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org> writes:

> [ adding Jeff directly since he has also been looking at
> infrastructure to track when MAP_SYNC should be disabled ]
>
> On Wed, Apr 25, 2018 at 7:21 AM, Dan Williams <dan.j.williams-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org> wrote:
>> On Wed, Apr 25, 2018 at 4:24 AM, Pankaj Gupta <pagupta-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org> wrote:
>>> This patch adds virtio-pmem driver for KVM
>>> guest.
>>
>> Minor nit, please expand your changelog line wrapping to 72 columns.
>>
>>>
>>> Guest reads the persistent memory range
>>> information from Qemu over VIRTIO and registers
>>> it on nvdimm_bus. It also creates a nd_region
>>> object with the persistent memory range
>>> information so that existing 'nvdimm/pmem'
>>> driver can reserve this into system memory map.
>>> This way 'virtio-pmem' driver uses existing
>>> functionality of pmem driver to register persistent
>>> memory compatible for DAX capable filesystems.
>>
>> We need some additional enabling to disable MAP_SYNC for this

enable to disable... I like it!  ;-)

>> configuration. In other words, if fsync() is required then we must
>> disable the MAP_SYNC optimization. I think this should be a struct
>> dax_device property looked up at mmap time in each MAP_SYNC capable
>> ->mmap() file operation implementation.

Ideally, qemu (seabios?) would advertise a platform capabilities
sub-table that doesn't fill in the flush bits.

-Jeff