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Re: [Qemu-devel] insmod virtio-blk is broken in qemu 1.0

From: Anthony Liguori
Subject: Re: [Qemu-devel] insmod virtio-blk is broken in qemu 1.0
Date: Mon, 19 Dec 2011 11:34:13 -0600
User-agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv: Gecko/20110922 Lightning/1.0b2 Thunderbird/3.1.15

On 12/19/2011 04:31 AM, Daniel P. Berrange wrote:
On Sat, Dec 17, 2011 at 11:49:56AM -0500, Kevin O'Connor wrote:
On Sat, Dec 17, 2011 at 10:24:07AM -0600, Anthony Liguori wrote:
On 12/17/2011 09:25 AM, Richard W.M. Jones wrote:
On Sat, Dec 17, 2011 at 09:22:45AM -0600, Anthony Liguori wrote:
I've even further narrowed it down to the presents or lack of '-vga
cirrus'.  If you add '-vga cirrus' to the above command line, the
guest will boot successfully.

Confirmed: Adding -vga cirrus to the command line cures it too.

That's a strange one :-)

vga sticks out a bit because it's one of the few places where we
treat device memory as ram as a performance optimization.

The only time vga has been touched in between v0.15 and v1.0 was
during the introduction of the memory API.

It's this commit:

commit d67c3f2cd92aed2247bfa8a9da61a902b7b2ff09
Author: Gerd Hoffmann<address@hidden>
Date:   Wed Aug 10 17:34:13 2011 +0200

     seabios: update to master

This looks like the same issue reported at:


The SeaBIOS fix for this was in rel- - but that didn't make
QEmu 1.0.  Does the problem go away if you upgrade to the newer
SeaBIOS version?

Sigh, we really need to be better about updating SeaBIOS in QEMU before
release. We had plenty of time to pull in a newer SeaBIOS before 1.0
that would have fixed this :-( was released on Nov 24th, which was actually after the soft feature freeze. We could have pulled 1.6.3 which was Oct 4th but updating the BIOS always results in some interesting things happening so it's not something I like to do unless we have to.

I'd rather have known that this functionality broken before that commit event went in to begin with than allowing it to remain broken until we happened to update past the bug.

We've had multiple releases now where
functionality is broken due to QEMU shipping with an older SeaBIOS
release than is available upstream.

I think the real issue here is testing. -nodefconfig -nodefaults is used by both libguestfs and libvirt but I'd wager to say that almost noone tests it in QEMU.

I thought about it quite a bit and what I came to was that we need to do a better job of making it easy to test these things, hence qemu-test that I just announced.


Anthony Liguori


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