Re: [Xen-devel] Fatal crash on xen4.2 HVM + qemu-xen dm + NFS

[Alex Bligh <alex@xxxxxxxxxxx>]

Konrad / Stefano,

Any update here?

I can't help but think a crashed dom0 and guaranteed domU corruption is
less bad than a theoretical data loss on a crash (not that we know
that theoretical possibility exists yet).

I'm currently using this trivial patch
https://github.com/abligh/qemu-upstream-4.2-testing-livemigrate/commit/a7d72
96aebc21af15074f3bf64c5c6795ca05f16

Alex


--On 5 February 2013 15:40:33 +0000 Alex Bligh <alex@xxxxxxxxxxx> wrote:

> Konrad / Stefano,
>
> Any movement / ideas on this one?
>
> Alex
>
> --On 25 January 2013 11:28:31 +0000 Alex Bligh <alex@xxxxxxxxxxx> wrote:
>
> > Konrad,
> >
> > --On 23 January 2013 16:29:20 +0000 Stefano Stabellini
> > <stefano.stabellini@xxxxxxxxxxxxx> wrote:
> >
> > > > diff --git a/hw/xen_disk.c b/hw/xen_disk.c
> > > > index a402ac8..1c3a6f5 100644
> > > > --- a/hw/xen_disk.c
> > > > +++ b/hw/xen_disk.c
> > > > @@ -603,7 +603,7 @@ static int blk_init(struct XenDevice *xendev)
> > > >      }
> > > >
> > > >      /* read-only ? */
> > > > -    qflags = BDRV_O_NOCACHE | BDRV_O_CACHE_WB | BDRV_O_NATIVE_AIO;
> > > > +    qflags = /* BDRV_O_NOCACHE | */ BDRV_O_CACHE_WB |
> > > > BDRV_O_NATIVE_AIO; if (strcmp(blkdev->mode, "w") == 0) {
> > > >          qflags |= BDRV_O_RDWR;
> > > >      } else {
> > > Before going for something like that I would like a confirmation from
> > > Konrad about blkfront behavior regarding barriers and
> > > BLKIF_OP_FLUSH_DISKCACHE. I certainly don't want to risk data
> > > corruptions.
> > Any ideas?
> >
> >
> > A slightly prettier patch would look like the one pasted
> > below (not sent with git-sendemail so beware whitespace issues).
> >
> > --
> > Alex Bligh
> >
> > commit a7d7296aebc21af15074f3bf64c5c6795ca05f16
> > Author: Alex Bligh <alex@xxxxxxxxxxx>
> > Date:   Thu Jan 24 09:41:34 2013 +0000
> >
> >     Disable use of O_DIRECT by default as it results in crashes.
> >
> >     See:
> >       http://lists.xen.org/archives/html/xen-devel/2012-12/msg01154.html
> >     for more details.
> >
> > diff --git a/hw/xen_disk.c b/hw/xen_disk.c
> > index a402ac8..a618d8d 100644
> > --- a/hw/xen_disk.c
> > +++ b/hw/xen_disk.c
> > @@ -45,6 +45,8 @@ static int batch_maps   = 0;
> >
> >  static int max_requests = 32;
> >
> > +static int use_o_direct = 0;
> > +
> >  /* ------------------------------------------------------------- */
> >
> >  # define BLOCK_SIZE  512
> > @@ -603,7 +605,7 @@ static int blk_init(struct XenDevice *xendev)
> >      }
> >
> >      /* read-only ? */
> > -    qflags = BDRV_O_NOCACHE | BDRV_O_CACHE_WB | BDRV_O_NATIVE_AIO;
> > +    qflags = (use_o_direct?BDRV_O_NOCACHE:0) | BDRV_O_CACHE_WB |
> > BDRV_O_NATIVE_AIO;
> >      if (strcmp(blkdev->mode, "w") == 0) {
> >          qflags |= BDRV_O_RDWR;
> >      } else {
>
>
> --
> Alex Bligh


--
Alex Bligh

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