Re: [Qemu-devel] [PATCH 09/26] ide: Set BSY bit during FLUSH

[Michael Roth <mdroth@linux.vnet.ibm.com>]

Quoting Michael Roth (2013-08-12 17:43:00)
> Quoting Alex Williamson (2013-07-03 16:51:56)
> > On Wed, 2013-07-03 at 15:16 -0500, Michael Roth wrote:
> > > On Wed, Jul 3, 2013 at 3:10 PM, Alex Williamson
> > > <alex.williamson@redhat.com> wrote:
> > > > On Wed, 2013-06-12 at 16:41 -0500, Michael Roth wrote:
> > > >> From: Andreas Färber <afaerber@suse.de>
> > > >>
> > > >> The implementation of the ATA FLUSH command invokes a flush at the block
> > > >> layer, which may on raw files on POSIX entail a synchronous fdatasync().
> > > >> This may in some cases take so long that the SLES 11 SP1 guest driver
> > > >> reports I/O errors and filesystems get corrupted or remounted read-only.
> > > >>
> > > >> Avoid this by setting BUSY_STAT, so that the guest is made aware we are
> > > >> in the middle of an operation and no ATA commands are attempted to be
> > > >> processed concurrently.
> > > >>
> > > >> Addresses BNC#637297.
> > > >>
> > > >> Suggested-by: Gonglei (Arei) <arei.gonglei@huawei.com>
> > > >> Signed-off-by: Andreas Färber <afaerber@suse.de>
> > > >> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
> > > >> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
> > > >> (cherry picked from commit f68ec8379e88502b4841a110c070e9b118d3151c)
> > > >>
> > > >> Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>
> > > >> ---
> > > >>  hw/ide/core.c |    1 +
> > > >>  1 file changed, 1 insertion(+)
> > > >>
> > > >> diff --git a/hw/ide/core.c b/hw/ide/core.c
> > > >> index c7a8041..9926d92 100644
> > > >> --- a/hw/ide/core.c
> > > >> +++ b/hw/ide/core.c
> > > >> @@ -814,6 +814,7 @@ void ide_flush_cache(IDEState *s)
> > > >>          return;
> > > >>      }
> > > >>
> > > >> +    s->status |= BUSY_STAT;
> > > >>      bdrv_acct_start(s->bs, &s->acct, 0, BDRV_ACCT_FLUSH);
> > > >>      bdrv_aio_flush(s->bs, ide_flush_cb, s);
> > > >>  }
> > > >
> > > > This caused a regression for me from 1.5.0->1.5.1.  Windows 7 x64 no
> > > > longer boots on q35 IDE with this change.  Thanks,
> > > 
> > > Are you seeing the issue for upstream builds as well?
> > 
> > Yes, I bisected this on upstream.  If i revert just this from 1.5.1, I
> > can boot again.  Upstream requires reverting this and a workaround for
> > 9afce429.  Thanks,
> 
> Does the problem still exist upstream? I'd rather not revert without a
> fix for the issue in 9afce429 since that might cause a regression for 1.5.1
> users now.

Ok, looks like we have a fix for this that was already sent to stable:

  a62eaa26c1d6d48fbdc3ac1d32bd1314f5fdc8c9

Could've sworn I searched master for a reference to f68ec837...

Will pull it in for 1.5.3

> 
> Sucks either way but I think it's safer to have Win7 not boot on q35 than
> re-introduce potential image corruption.
> 
> > 
> > Alex