Re: [Qemu-devel] qemu/qemu-kvm floppy regression brought by 212ec7baa28cc9d819234fed1541fc1423cfe3d8

[Lucas Meneghel Rodrigues]

On 10/27/2011 11:17 PM, Zhi Yong Wu wrote:
> On Fri, Oct 28, 2011 at 2:57 AM, Lucas Meneghel Rodrigues
> <address@hidden>  wrote:
> > On 10/27/2011 05:17 AM, Stefan Hajnoczi wrote:
> > > On Wed, Oct 26, 2011 at 03:19:17PM -0200, Lucas Meneghel Rodrigues wrote:
> > > > On 10/26/2011 01:47 PM, Kevin Wolf wrote:
> > > > > Am 26.10.2011 16:41, schrieb Lucas Meneghel Rodrigues:
> > > > > > Hi folks:
> > > > > >
> > > > > > We've captured a regression with floppy disk on recent qemu (and
> > > > > > qemu-kvm, after a code merge). We bisected it to be caused by:
> > > > > >
> > > > > > commit 212ec7baa28cc9d819234fed1541fc1423cfe3d8
> > > > > > Author: Richard Henderson<address@hidden>
> > > > > > Date:   Mon Aug 15 15:08:45 2011 -0700
> > > > > >
> > > > > >       fdc: Convert to isa_register_portio_list
> > > > > >
> > > > > >       Signed-off-by: Richard Henderson<address@hidden>
> > > > > >       Signed-off-by: Avi Kivity<address@hidden>
> > > > > >
> > > > > > Since this commit, the guest doesn't see a floppy disk attached to it
> > > > > > anymore, blocking kvm autotest ability to install windows guests
> > > > > > automatically. This is a big deal for kvm autotest (ruins our automated
> > > > > > regression jobs), so please take a look at it.
> > > > >
> > > > > Can you please try again with the latest block branch? I think there is
> > > > > a patch queued that will fix it.
> > > >
> > > > Kevin, I did try with HEAD of your repo:
> > > >
> > > > git://repo.or.cz/qemu/kevin.git
> > > >
> > > > address@hidden qemu-kwolf]$ git branch -r
> > > >    origin/HEAD ->    origin/master
> > > >    origin/blkqueue
> > > >    origin/blkqueue-v1
> > > >    origin/block
> > > >    origin/coroutine
> > > >    origin/coroutine-block
> > > >    origin/coroutine-devel
> > > >    origin/devel
> > > >    origin/ehci
> > > >    origin/for-anthony
> > > >    origin/for-stable-0.14
> > > >    origin/inplace-conversion
> > > >    origin/master
> > > >
> > > > With this repo, master branch, the problem persists. With the block
> > > > branch, the problem persists.
> > > >
> > > > Now, with the blkqueue branch the problem is resolved. Cleber had
> > > > the same results booting a FreeDOS floppy. So the fix is indeed in
> > > > blkqueue.
> > > >
> > > > Oh, you might want to check the blkqueue branch, it does have quite
> > > > a bunch of set but unused variables, which will cause compilation
> > > > errors unless --disable-werror is passed to the configure script.
> > >
> > > I think blkqueue is an older development branch of the "block queue"
> > > feature that Kevin was working on.  It is not Kevin's block tree (see
> > > his "block" branch).
> >
> > So no, the block branch does not resolve the floppy access problem.
> >
> > Well, considering the tests of the stable set I'm running against qemu right
> > now, this is not the biggest of our problems... I'm verifying qemu is
> > segfaulting on nearly every prolonged attempt of doing migration... I'm
> > about to write an email about it.
> What is the OS of your guest? fedora16 or RHEL6? I would like recently
> to use floppy device in guest.

Ok, correcting my answer, it was Windows 7 SP1. For some reason, I read 
'host' instead of guest. I had a long day when I wrote the 1st reply.

It's been a while that we've verified that the linux floppy driver is 
quite unstable. In general linux + floppy devices on a guest tends to 
crash the guest kernel, and that's why in kvm autotest we moved from 
floppy devices to cdroms to hold the kickstart file. The fact you 
managed to get things working under F14 means you are lucky, and that 
particular floppy driver bug does not happen under F14's kernel. We 
never had such a kernel crash problem with any of the Windows's kernels.

So if I were you, I would *not* use a floppy with a linux guest. Well, 
unless you want to debug the floppy driver bug and fix this on upstream 
linux once for all, so future versions of linux won't have this problem.