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


From: Shawn Starr
Subject: Re: [Qemu-devel] EHCI USB regression in 1.2.0 - ehci_state_fetchqtd() asserting
Date: Mon, 08 Oct 2012 16:18:08 -0400
User-agent: KMail/4.9.2 (Linux/3.6.0-0.rc7.git0.1.fc18.x86_64; KDE/4.9.2; x86_64; ; )

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

Thanks,
Shawn.

> Regards,
> 
> Hans



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