Re: [Qemu-devel] EHCI USB regression in 1.2.0 - ehci_state_fetchqtd() asserting

[Shawn Starr]

On Monday, October 08, 2012 11:32:54 PM Hans de Goede wrote:
> Hi,
> 
> On 10/08/2012 10:18 PM, Shawn Starr wrote:
> > On Monday, October 08, 2012 10:10:49 PM Hans de Goede wrote:
> >> Hi,
> >> 
> >> On 10/08/2012 06:11 PM, Johannes Stezenbach wrote:
> >> 
> >> <mega snip>
> >> 
> >>   > I also wonder if this is not a generic problem
> >>> 
> >>> for all emulated hw if the driver uses some timeout?
> >> 
> >> Yes it likely is, because the emulated timer interrupt will
> >> try to make up for time lost when the vm was not running
> >> (in either hypervisor or guest mode), while as hw emulation
> >> code which has been pre-empted for what ever reason my
> >> simply need some more actual running time before it can
> >> complete the task as hand, at which point the timeout
> >> will trigger sooner then the hw emulation can handle the
> >> task ...
> >> 
> >> Note that with the EHCI emulation we also can have the
> >> 2 (guest and hw-emulation time) get out of sync in the
> >> other way. When we got behind in processing frames
> >> on the periodic schedule compared to "real-time" we would
> >> catch up too fast, causing the guest to see large
> >> jumps in the frindex register, which it does not like.
> >> 
> >> So all of this really is a precarious balancing act, and
> >> to get back to the subject of the thread, the latency
> >> spikes some of the kernels debugging options can cause,
> >> can upset the balance...
> > 
> > Hello folks,
> > 
> > I am using a non-debug kernel (because debug kernels are seriously
> > sluggish). I may elect to get kernel-3.6.0-3.fc18 or  kernel-3.6.1-1.fc18
> > from koji also since 3.6 is final now.
> > 
> > Currently using: 3.6.0-0.rc7.git0.1.fc18.x86_64
> 
> Hmm, so were you using this at the time you hit the bug you reported
> earlier too ? And can you reproduce that bug or was it a one
> time occurence ?
> 

Need to retry, I triggered this with yahoo IM client in VM. I'll just go to 
3.6.1 and try this again this week. When I did trigger this with  
3.6.0-0.rc7.git0.1.fc18, it was repeatable.

Thanks,
Shawn.

> Regards,
> 
> Hans