Re: [Qemu-devel] [PATCH for-2.13] pc-bios/s390-ccw: Increase virtio timeout to 30 seconds

[Cornelia Huck <cohuck@redhat.com>]

On Thu, 29 Mar 2018 12:03:42 +0200
Christian Borntraeger <borntraeger@de.ibm.com> wrote:

> On 03/29/2018 11:37 AM, Thomas Huth wrote:
> > The current timeout is set to only three seconds - and considering that
> > vring_wait_reply() or rather get_second() is not doing any rounding,
> > the real timeout is likely rather 2 seconds in most cases. When the
> > host is really badly loaded and we run the guest in TCG mode instead
> > of KVM, it's possible that we hit this timeout by mistake. So let's
> > increase the timeout to 30 seconds instead to ease this situation (30
> > seconds is also the timeout that is used by the Linux SCSI subsystem
> > for example, so this seems to be a sane value for block IO timeout).  
> 
> I have never seen this, but cant this also with KVM (e.g. host paging
> and the swap disk is busy for some seconds).

It's probably less likely, but I don't see why not. 30s sounds like a
more forgiving value.

> 
> Wouldnt it also qualify for 2.12?

I can queue it (and a bios rebuild) to s390-fixes, it's certainly
reasonable.

Else,

Reviewed-by: Cornelia Huck <cohuck@redhat.com>

> 
> > 
> > Buglink: https://bugzilla.redhat.com/show_bug.cgi?id=1549079
> > Signed-off-by: Thomas Huth <thuth@redhat.com>
> > ---
> >  pc-bios/s390-ccw/virtio.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/pc-bios/s390-ccw/virtio.c b/pc-bios/s390-ccw/virtio.c
> > index 817e7f5..cdb66f4 100644
> > --- a/pc-bios/s390-ccw/virtio.c
> > +++ b/pc-bios/s390-ccw/virtio.c
> > @@ -14,7 +14,7 @@
> >  #include "virtio-scsi.h"
> >  #include "bswap.h"
> > 
> > -#define VRING_WAIT_REPLY_TIMEOUT 3
> > +#define VRING_WAIT_REPLY_TIMEOUT 30
> > 
> >  static VRing block[VIRTIO_MAX_VQS];
> >  static char ring_area[VIRTIO_RING_SIZE * VIRTIO_MAX_VQS]
> >   
>