From: Pankaj Gupta <pagupta-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
To: Stefan Hajnoczi <stefanha-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
Cc: jack-AlSwsSmVLrQ@public.gmane.org,
kvm-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
david-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org,
Stefan Hajnoczi
<stefanha-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>,
ross zwisler
<ross.zwisler-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>,
qemu-devel-qX2TKyscuCcdnm+yROfE0A@public.gmane.org,
lcapitulino-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org,
linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org,
niteshnarayanlal-PkbjNfxxIARBDgjK7y7TUQ@public.gmane.org,
mst-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org,
hch-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org,
linux-nvdimm-y27Ovi1pjclAfugRpC6u6w@public.gmane.org,
marcel-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org,
nilal-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org,
riel-ebMLmSuQjDVBDgjK7y7TUQ@public.gmane.org,
pbonzini-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org,
kwolf-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org,
xiaoguangrong eric
<xiaoguangrong.eric-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>,
linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
imammedo-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org
Subject: Re: [Qemu-devel] [RFC v2 1/2] virtio: add pmem driver
Date: Sat, 28 Apr 2018 06:48:41 -0400 (EDT) [thread overview]
Message-ID: <1266554822.23475618.1524912521209.JavaMail.zimbra@redhat.com> (raw)
In-Reply-To: <20180427133146.GB11150-lxVrvc10SDRcolVlb+j0YCZi+YwRKgec@public.gmane.org>
> > > > + int err;
> > > > +
> > > > + sg_init_one(&sg, buf, sizeof(buf));
> > > > +
> > > > + err = virtqueue_add_outbuf(vpmem->req_vq, &sg, 1, buf, GFP_KERNEL);
> > > > +
> > > > + if (err) {
> > > > + dev_err(&vdev->dev, "failed to send command to virtio pmem
> > > > device\n");
> > > > + return;
> > > > + }
> > > > +
> > > > + virtqueue_kick(vpmem->req_vq);
> > >
> > > Is any locking necessary? Two CPUs must not invoke virtio_pmem_flush()
> > > at the same time. Not sure if anything guarantees this, maybe you're
> > > relying on libnvdimm but I haven't checked.
> >
> > I thought about it to some extent, and wanted to go ahead with simple
> > version first:
> >
> > - I think file 'inode -> locking' sill is there for request on single file.
> > - For multiple files, our aim is to just flush the backend block image.
> > - Even there is collision for virt queue read/write entry it should just
> > trigger a Qemu fsync.
> > We just want most recent flush to assure guest writes are synced
> > properly.
> >
> > Important point here: We are doing entire block fsync for guest virtual
> > disk.
>
> I don't understand your answer. Is locking necessary or not?
It will be required with other changes.
>
> From the virtqueue_add_outbuf() documentation:
>
> * Caller must ensure we don't call this with other virtqueue operations
> * at the same time (except where noted).
Yes, I also saw it. But thought if can avoid it with current functionality. :)
Thanks,
Pankaj
next prev parent reply other threads:[~2018-04-28 10:48 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-04-25 11:24 [RFC v2 0/2] kvm "fake DAX" device flushing Pankaj Gupta
[not found] ` <20180425112415.12327-1-pagupta-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
2018-04-25 11:24 ` [RFC v2 1/2] virtio: add pmem driver Pankaj Gupta
[not found] ` <20180425112415.12327-2-pagupta-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
2018-04-25 14:21 ` Dan Williams
[not found] ` <CAPcyv4hvrB08XPTbVK0xT2_1Xmaid=-v3OMxJVDTNwQucsOHLA-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2018-04-25 14:43 ` Dan Williams
[not found] ` <CAPcyv4hiowWozV527sQA_e4fdgCYbD6xfG==vepAqu0hxQEQcw-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2018-04-26 12:27 ` Jeff Moyer
[not found] ` <x49o9i6885e.fsf-RRHT56Q3PSP4kTEheFKJxxDDeQx5vsVwAInAS/Ez/D0@public.gmane.org>
2018-04-26 17:15 ` [Qemu-devel] " Pankaj Gupta
[not found] ` <1499190564.23017177.1524762938762.JavaMail.zimbra-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
2018-04-26 17:24 ` Jeff Moyer
2018-04-25 14:52 ` Michael S. Tsirkin
[not found] ` <20180425174705-mutt-send-email-mst-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
2018-04-25 15:11 ` [Qemu-devel] " Pankaj Gupta
2018-04-26 13:12 ` Stefan Hajnoczi
[not found] ` <20180426131236.GA30991-lxVrvc10SDRcolVlb+j0YCZi+YwRKgec@public.gmane.org>
2018-04-26 15:44 ` Pankaj Gupta
2018-04-27 13:31 ` Stefan Hajnoczi
[not found] ` <20180427133146.GB11150-lxVrvc10SDRcolVlb+j0YCZi+YwRKgec@public.gmane.org>
2018-04-28 10:48 ` Pankaj Gupta [this message]
2018-04-25 11:24 ` [RFC v2 2/2] pmem: device flush over VIRTIO Pankaj Gupta
[not found] ` <20180425112415.12327-3-pagupta-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
2018-04-25 14:23 ` Dan Williams
[not found] ` <CAPcyv4gpZzKfE7jY1peYOVd6sVhNz7jce1s_xNH_2Lt8AjRK-Q-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2018-04-25 14:47 ` Pankaj Gupta
2018-04-26 13:15 ` Stefan Hajnoczi
[not found] ` <20180426131517.GB30991-lxVrvc10SDRcolVlb+j0YCZi+YwRKgec@public.gmane.org>
2018-04-26 16:40 ` Pankaj Gupta
[not found] ` <58645254.23011245.1524760853269.JavaMail.zimbra-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
2018-04-26 16:57 ` Dan Williams
[not found] ` <CAPcyv4jv-hJNKJxak98T7aCnWztVEDTE8o=8fjvOrVmrTfyjdA-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2018-04-26 17:13 ` Pankaj Gupta
2018-04-25 11:24 ` [RFC v2] qemu: Add virtio pmem device Pankaj Gupta
[not found] ` <20180425112415.12327-4-pagupta-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
2018-04-25 11:35 ` [Qemu-devel] " no-reply-isE1Te71pDtAfugRpC6u6w
2018-04-25 11:58 ` Pankaj Gupta
2018-04-25 14:23 ` Eric Blake
[not found] ` <79f72139-0fcb-3d5e-a16c-24f3b5ee1a07-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
2018-04-25 14:51 ` Pankaj Gupta
2018-04-25 11:46 ` no-reply
2018-04-25 14:25 ` Eric Blake
[not found] ` <25f3e433-cfa6-4a62-ba7f-47aef1119dfc-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
2018-04-25 14:55 ` Pankaj Gupta
2018-04-26 13:24 ` Stefan Hajnoczi
[not found] ` <20180426132406.GC30991-lxVrvc10SDRcolVlb+j0YCZi+YwRKgec@public.gmane.org>
2018-04-26 16:43 ` [Qemu-devel] " Pankaj Gupta
2018-06-01 12:24 ` [Qemu-devel] [RFC v2 0/2] kvm "fake DAX" device flushing Igor Mammedov
[not found] ` <20180601142410.5c986f13-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
2018-06-04 5:56 ` Pankaj Gupta
2018-06-04 9:55 ` David Hildenbrand
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=1266554822.23475618.1524912521209.JavaMail.zimbra@redhat.com \
--to=pagupta-h+wxahxf7alqt0dzr+alfa@public.gmane.org \
--cc=david-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org \
--cc=hch-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org \
--cc=imammedo-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org \
--cc=jack-AlSwsSmVLrQ@public.gmane.org \
--cc=kvm-u79uwXL29TY76Z2rM5mHXA@public.gmane.org \
--cc=kwolf-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org \
--cc=lcapitulino-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=marcel-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org \
--cc=mst-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org \
--cc=nilal-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org \
--cc=niteshnarayanlal-PkbjNfxxIARBDgjK7y7TUQ@public.gmane.org \
--cc=pbonzini-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org \
--cc=qemu-devel-qX2TKyscuCcdnm+yROfE0A@public.gmane.org \
--cc=riel-ebMLmSuQjDVBDgjK7y7TUQ@public.gmane.org \
--cc=ross.zwisler-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org \
--cc=stefanha-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org \
--cc=stefanha-Re5JQEeQqe8AvxtiuMwx3w@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).