From: Amit Shah <amit.shah@redhat.com>
To: Rusty Russell <rusty@rustcorp.com.au>
Cc: Virtualization List <virtualization@lists.linux-foundation.org>
Subject: Re: [PATCH] virtio: Decrement avail idx on buffer detach
Date: Mon, 28 Mar 2011 19:57:06 +0530 [thread overview]
Message-ID: <20110328142706.GA2949@amit-x200.redhat.com> (raw)
In-Reply-To: <20110317122659.GB18382@amit-x200.redhat.com>
On (Thu) 17 Mar 2011 [17:56:59], Amit Shah wrote:
> On (Thu) 17 Mar 2011 [15:26:28], Rusty Russell wrote:
> > On Wed, 16 Mar 2011 19:12:10 +0530, Amit Shah <amit.shah@redhat.com> wrote:
> > > When detaching a buffer from a vq, the avail.idx value should be
> > > decremented as well.
> > >
> > > This was noticed by hot-unplugging a virtio console port and then
> > > plugging in a new one on the same number (re-using the vqs which were
> > > just 'disowned'). qemu reported
> > >
> > > 'Guest moved used index from 0 to 256'
> > >
> > > when any IO was attempted on the new port.
> >
> > Yech... detach_unused_buf cannot be used on a live virtqueue; it assumes
> > we will reset the vq (usually by resetting the entire device).
> >
> > You've partially violated that assumption by reusing the vq after
> > calling detach_unused_buf. So I'm not entirely sure this is the only
> > bug lurking; safer would be to re-initialize the vq somehow when you
> > plug back in...
>
> Right; and then that will need host changes too (re-init the vqs on
> the host side), which then gets us into compat problems...
Rusty, any thoughts on this?
Amit
next prev parent reply other threads:[~2011-03-28 14:27 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <a2fe5813ccecf1e762670702cba8ccb2a4cb8cfc.1300282928.git.amit.shah@redhat.com>
2011-03-17 4:56 ` [PATCH] virtio: Decrement avail idx on buffer detach Rusty Russell
2011-03-17 12:26 ` Amit Shah
2011-03-28 14:27 ` Amit Shah [this message]
2011-04-04 6:34 ` Rusty Russell
2011-04-04 15:01 ` Amit Shah
2011-03-16 13:42 Amit Shah
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=20110328142706.GA2949@amit-x200.redhat.com \
--to=amit.shah@redhat.com \
--cc=rusty@rustcorp.com.au \
--cc=virtualization@lists.linux-foundation.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).