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Re: [Xen-devel] no default ioreq server?


  • To: Jan Beulich <JBeulich@xxxxxxxx>
  • From: Paul Durrant <Paul.Durrant@xxxxxxxxxx>
  • Date: Fri, 12 Jun 2015 15:39:28 +0000
  • Accept-language: en-GB, en-US
  • Cc: xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxxx>
  • Delivery-date: Fri, 12 Jun 2015 15:39:46 +0000
  • List-id: Xen developer discussion <xen-devel.lists.xen.org>
  • Thread-index: AQHQpR3x8VCSjjTfskC7QxZulLYu5Z2o/4vg
  • Thread-topic: no default ioreq server?

> -----Original Message-----
> From: Jan Beulich [mailto:JBeulich@xxxxxxxx]
> Sent: 12 June 2015 15:41
> To: Paul Durrant
> Cc: xen-devel
> Subject: no default ioreq server?
> 
> Paul,
> 
> looks like guests nowadays run without a default ioreq server. Is
> that intended to be that way? Having noticed it and having looked
> at qemuu I certainly can't see how one would be set up. Yet
> without one send_timeoffset_req() can't possibly work, and after
> having seen "Unsuccessful timeoffset update" every once in a while
> over the last couple of weeks I finally took the time to look into
> what this would be caused by. Considering that reading the
> respective HVM params appears to be intentionally bypassed by
> qemuu, I also can't immediately see how this should be fixed.
> 

Jan,

  Upstream QEMU actually ignored these ioreqs anyway (see 
http://xenbits.xen.org/gitweb/?p=staging/qemu-upstream-unstable.git;f=xen-hvm.c;hb=HEAD#l951),
 so I wasn't too worried that there was any regression in moving away from it 
being a default server. I agree the printks are a bit annoying though (and they 
are straight printks rather than gdprintks).

  I guess there's a couple of ways to tackle it. Either we have another hvm op 
to allow an emulator to ask for TIMEOFFSET ioreqs, or we just broadcast them. 
The latter is pretty simple to implement.

  Paul

> Thanks, Jan


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