Re: [Xen-devel] [PATCH v3 4/4] xen-blkback: support dynamic unbind/bind

[Jürgen Groß <jgross@xxxxxxxx>]

On 12.12.19 12:46, Roger Pau Monné wrote:
> On Wed, Dec 11, 2019 at 03:29:56PM +0000, Paul Durrant wrote:
> > By simply re-attaching to shared rings during connect_ring() rather than
> > assuming they are freshly allocated (i.e assuming the counters are zero)
> > it is possible for vbd instances to be unbound and re-bound from and to
> > (respectively) a running guest.
> >
> > This has been tested by running:
> >
> > while true;
> >    do fio --name=randwrite --ioengine=libaio --iodepth=16 \
> >    --rw=randwrite --bs=4k --direct=1 --size=1G --verify=crc32;
> >    done
> >
> > in a PV guest whilst running:
> >
> > while true;
> >    do echo vbd-$DOMID-$VBD >unbind;
> >    echo unbound;
> >    sleep 5;
> >    echo vbd-$DOMID-$VBD >bind;
> >    echo bound;
> >    sleep 3;
> >    done
> >
> > in dom0 from /sys/bus/xen-backend/drivers/vbd to continuously unbind and
> > re-bind its system disk image.
> >
> > This is a highly useful feature for a backend module as it allows it to be
> > unloaded and re-loaded (i.e. updated) without requiring domUs to be halted.
> > This was also tested by running:
> >
> > while true;
> >    do echo vbd-$DOMID-$VBD >unbind;
> >    echo unbound;
> >    sleep 5;
> >    rmmod xen-blkback;
> >    echo unloaded;
> >    sleep 1;
> >    modprobe xen-blkback;
> >    echo bound;
> >    cd $(pwd);
> >    sleep 3;
> >    done
> >
> > in dom0 whilst running the same loop as above in the (single) PV guest.
> >
> > Some (less stressful) testing has also been done using a Windows HVM guest
> > with the latest 9.0 PV drivers installed.
> >
> > Signed-off-by: Paul Durrant <pdurrant@xxxxxxxxxx>
> Reviewed-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
>
> Thanks!
>
> Juergen: I guess you will also pick this series and merge it from the
> Xen tree instead of the block one?
Yes.


Juergen

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