From: Stefan Hajnoczi <stefanha-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
To: Dan Williams <dan.j.williams-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
Cc: Kevin Wolf <kwolf-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>,
Pankaj Gupta <pagupta-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>,
Jan Kara <jack-AlSwsSmVLrQ@public.gmane.org>,
xiaoguangrong eric
<xiaoguangrong.eric-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>,
KVM list <kvm-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
linux-nvdimm
<linux-nvdimm-y27Ovi1pjclAfugRpC6u6w@public.gmane.org>,
David Hildenbrand <david-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>,
ross zwisler
<ross.zwisler-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>,
"linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org"
<linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
Qemu Developers
<qemu-devel-qX2TKyscuCcdnm+yROfE0A@public.gmane.org>,
Christoph Hellwig <hch-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>,
Linux MM <linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org>,
Stefan Hajnoczi
<stefanha-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>,
Paolo Bonzini <pbonzini-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>,
Nitesh Narayan Lal
<nilal-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
Subject: Re: [Qemu-devel] [RFC 2/2] KVM: add virtio-pmem driver
Date: Thu, 19 Oct 2017 10:01:46 +0200 [thread overview]
Message-ID: <20171019080146.GA3503@stefanha-x1.localdomain> (raw)
In-Reply-To: <CAPcyv4h6aFkyHhh4R4DTznbSCLf9CuBoszk0Q1gB5EKNcp_SeQ-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
On Wed, Oct 18, 2017 at 08:51:37AM -0700, Dan Williams wrote:
> On Wed, Oct 18, 2017 at 6:03 AM, Stefan Hajnoczi <stefanha-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
> > On Tue, Oct 17, 2017 at 04:30:41AM -0400, Pankaj Gupta wrote:
> >>
> >> > > Are you saying do it as existing i.e ACPI pmem like interface?
> >> > > The reason we have created this new driver is exiting pmem driver
> >> > > does not define proper semantics for guest flushing requests.
> >> >
> >> > At this point I'm caring about the Linux-internal interface, and
> >> > for that it should be integrated into the nvdimm subsystem and not
> >> > a block driver. How the host <-> guest interface looks is a different
> >> > idea.
> >> >
> >> > >
> >> > > Regarding block support of driver, we want to achieve DAX support
> >> > > to bypass guest page cache. Also, we want to utilize existing DAX
> >> > > capable file-system interfaces(e.g fsync) from userspace file API's
> >> > > to trigger the host side flush request.
> >> >
> >> > Well, if you want to support XFS+DAX better don't make it a block
> >> > devices, because I'll post patches soon to stop using the block device
> >> > entirely for the DAX case.
> >>
> >> o.k I will look at your patches once they are in mailing list.
> >> Thanks for the heads up.
> >>
> >> If I am guessing it right, we don't need block device additional features
> >> for pmem? We can bypass block device features like blk device cache flush etc.
> >> Also, still we would be supporting ext4 & XFS filesystem with pmem?
> >>
> >> If there is time to your patches can you please elaborate on this a bit.
> >
> > I think the idea is that the nvdimm subsystem already adds block device
> > semantics on top of the struct nvdimms that it manages. See
> > drivers/nvdimm/blk.c.
> >
> > So it would be cleaner to make virtio-pmem an nvdimm bus. This will
> > eliminate the duplication between your driver and drivers/nvdimm/ code.
> > Try "git grep nvdimm_bus_register" to find drivers that use the nvdimm
> > subsystem.
>
> This use case is not "Persistent Memory". Persistent Memory is
> something you can map and make persistent with CPU instructions.
> Anything that requires a driver call is device driver managed "Shared
> Memory".
Dan, in that case do you have ideas regarding Christoph Hellwig's
comment that this driver should be integrated into the nvdimm subsystem
instead of a new block driver?
Stefan
next prev parent reply other threads:[~2017-10-19 8:01 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-10-12 15:50 [RFC 0/2] KVM "fake DAX" device flushing Pankaj Gupta
2017-10-12 15:50 ` [RFC 1/2] pmem: Move reusable code to base header files Pankaj Gupta
2017-10-12 20:42 ` Dan Williams
2017-10-12 21:27 ` [Qemu-devel] " Pankaj Gupta
[not found] ` <20171012155027.3277-1-pagupta-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
2017-10-12 15:50 ` [RFC 2/2] KVM: add virtio-pmem driver Pankaj Gupta
2017-10-12 20:51 ` Dan Williams
2017-10-12 21:25 ` Pankaj Gupta
2017-10-12 21:54 ` Dan Williams
[not found] ` <CAPcyv4gkri7t+3Unf0sc9AHMnz-v9G_qV_bJppLjUUNAn7drrQ-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2017-10-12 22:18 ` Pankaj Gupta
2017-10-12 22:27 ` Rik van Riel
2017-10-12 22:39 ` Pankaj Gupta
2017-10-12 22:52 ` Pankaj Gupta
2017-10-12 22:59 ` Dan Williams
2017-10-12 23:07 ` Pankaj Gupta
2017-10-13 9:44 ` Stefan Hajnoczi
2017-10-13 10:48 ` Pankaj Gupta
[not found] ` <24301306.20068579.1507891695416.JavaMail.zimbra-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
2017-10-16 14:47 ` Stefan Hajnoczi
2017-10-16 15:58 ` Dan Williams
2017-10-16 17:04 ` Pankaj Gupta
[not found] ` <20171013094431.GA27308-lxVrvc10SDRcolVlb+j0YCZi+YwRKgec@public.gmane.org>
2017-10-13 15:25 ` Dan Williams
[not found] ` <20171012155027.3277-3-pagupta-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
2017-10-17 7:16 ` Christoph Hellwig
2017-10-17 7:40 ` [Qemu-devel] " Pankaj Gupta
2017-10-17 8:02 ` Christoph Hellwig
2017-10-17 8:30 ` Pankaj Gupta
2017-10-18 13:03 ` Stefan Hajnoczi
2017-10-18 15:51 ` Dan Williams
[not found] ` <CAPcyv4h6aFkyHhh4R4DTznbSCLf9CuBoszk0Q1gB5EKNcp_SeQ-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2017-10-19 8:01 ` Stefan Hajnoczi [this message]
2017-10-19 8:01 ` Christoph Hellwig
[not found] ` <20171019080149.GB10089-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>
2017-10-19 18:21 ` Dan Williams
[not found] ` <CAPcyv4j=Cdp68C15HddKaErpve2UGRfSTiL6bHiS=3gQybz9pg-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2017-10-20 8:00 ` Christoph Hellwig
[not found] ` <20171020080049.GA25471-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>
2017-10-20 15:05 ` Dan Williams
2017-10-20 16:06 ` Christoph Hellwig
2017-10-20 16:11 ` Dan Williams
2017-10-12 15:50 ` [RFC] QEMU: Add virtio pmem device Pankaj Gupta
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20171019080146.GA3503@stefanha-x1.localdomain \
--to=stefanha-re5jqeeqqe8avxtiumwx3w@public.gmane.org \
--cc=dan.j.williams-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org \
--cc=david-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org \
--cc=hch-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org \
--cc=jack-AlSwsSmVLrQ@public.gmane.org \
--cc=kvm-u79uwXL29TY76Z2rM5mHXA@public.gmane.org \
--cc=kwolf-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org \
--cc=linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org \
--cc=linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org \
--cc=linux-nvdimm-y27Ovi1pjclAfugRpC6u6w@public.gmane.org \
--cc=nilal-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org \
--cc=pagupta-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org \
--cc=pbonzini-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org \
--cc=qemu-devel-qX2TKyscuCcdnm+yROfE0A@public.gmane.org \
--cc=ross.zwisler-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org \
--cc=stefanha-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org \
--cc=xiaoguangrong.eric-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).