Re: [win-pv-devel] xenvbd (8.x) - blkback/tapdisk3 problems

[Martin Cerveny <martin@xxxxxxxxx>]

Hello.

Thanks, for response.

On Fri, 28 Oct 2016, Paul Durrant wrote:
> > -----Original Message-----
> > I have problems with xenvbd (8.x). There was NOT problem with older pv-
> > drivers xenvbd (7.2x).
> > Questions @ bottom.
> >
> > I use remote raw disk as source (multipath+iscsi+iser+ib).
> > Two configs:
> >
> > --------------------------
> >
> > 1) use direct blkback (format=raw, vdev=hda, access=rw,
> > target=/dev/mapper/3600144f07a0542580000568ba94a0001)
> >
> > Performance is good, but __unusable__ for working.
> >
> > Every few seconds/minutes (randomly, depends on disk load) the windows
> > hung on io-operations. I usually saw this more often during write operations.
> >
> > Sometimes (1:10) I saw "PdoReset" in "DebugView" (DomU):
> >
> > 00003034        10:12:32        XENVBD|__PdoReset:Target[0] ====>
> > 00003054        10:12:53        XENVBD|__PdoReset:Target[0] <====
> >
> > There is also restart log in Dom0, but no errors on disks/iscsi:
> >
> > [ 3919.034421] xen-blkback:backend/vbd/3/768: prepare for reconnect
> > [ 3919.039869] xen-blkback:ring-ref 32, event-channel 40, protocol 1 (x86_64-
> > abi)
> Yes, XENVBD is being asked to reset because Windows thinks the storage 
> is stalled and it looks like it was probably right. Suggests a loss of 
> event notification somewhere.
Ok, I suppose Dom0 logs are result of DomU reset, no problem.

> > Enviroments:
> > - Windows7 x64
> > - tested signed winpv drivers 8.1 and primary on development drivers 8.2
> > - xen 4.5.3, 4.6 and primary 4.7.0
> > - kernels "XenServer" - kernel-3.10.41-353.380450 (and others from XS6.5)
> > and kernel-3.10.96-495.383045.x86_64 (and others from XS7)
> > - blktap3 - blktap-3.0.0.xs1001-xs6.5.0 and blktap-3.2.0.xs1087-xs7.0.0.x86_64
> >
> > ---------------------
> >
> > Questions:
> >
> > What is buggy in "direct blkback" chain ?
> No idea. Possibly blkback, possibly the underlying storage. Your kernels are 
> old and blkback has undergone many changes in more recent kernels.
(I suppose that XS-kernel is super-tuned for Dom0 and there won't be such 
problem).

Now updated Dom0:
- fedora 24 + update
- kernel - 4.7.9-200.fc24.x86_64
- xen 4.7.0 + some backports from XS

The problem is the same.
When were "changes" to blkback applied ?

> > Was it tested ?
> By XenServer? No. XenServer makes no use of blkback.
:-((( (I see few patches to blkback 
(https://github.com/xenserver/linux-3.x.pg/tree/master/master))

Thanks for answers or hints, Martin Cerveny

>  Paul
> > Thanks for answers, Martin Cerveny
> >
> > _______________________________________________
> > win-pv-devel mailing list
> > win-pv-devel@xxxxxxxxxxxxxxxxxxxx
> > https://lists.xenproject.org/cgi-bin/mailman/listinfo/win-pv-devel
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