Re: [Xen-devel] Xen 4.2.0-rc4 issues with DVB tuner

[Sander Eikelenboom <linux@xxxxxxxxxxxxxx>]

Tuesday, September 18, 2012, 5:12:28 PM, you wrote:

> On Tue, Sep 18, 2012 at 4:33 PM, Sander Eikelenboom
> <linux@xxxxxxxxxxxxxx> wrote:

>>>>> What I donÂt understand is how graphics pass through even works
>>>> and a tuner
>>>>> card has problems due to the introduced latencies in the
>>>> IRQs.
>>>>
>>>> Do you have
>>>>> any more info about this?
>>>>
>>>> In this respect sound is harder than graphics. Try pinning your dom0 to a
>>>> CPU core, and set affinities on other domains so that dom0 does not compete
>>>> for the core with any other domains.
>>
>>> All right, I can try that. However, the problem happens without any
>>> domU running, just
>>> the dom0. Do you still think that pinning to a cpu core or setting
>>> affinities can help?
>>
>> I haven't followed the thread closely, but are you sure the device works OK 
>> on baremetal (linux without xen) ?
>> If you have problems in dom0 it seems it hasn't got much to do with 
>> passthrough ?

> You are right, I havenÂt reached the point of trying to passthrough it
> to a domU.

> IÂm sure the device works fine on bare metal. I have it working on an
> HTPC which makes 2-3
> recordings per day, without issues.

But that is a different machine, but with the same card ?
If that's right it would also try baremetal first on the same machine and card 
you are trying to get it to work with xen.

> On the linux media mailing list I was said this problem was common
> with all tuner cards,
> more generally with any card which generates lots of interruptions and
> that I should better
> forget about it.

Hmm that's a quite standard answer for not standard cases :-)

I have and have had multiple devices passed through, and it's working quite 
good, sound card, a analog tv tuner and a 8 channel dvr card.

Since it's a DVB card, i'm also wondering on what resolution you are trying to 
grab video, perhaps first try it on a quite low resolution (requiring less 
throughput and processing power), and if you are trying to transcode stuff 
directly.

--
Sander



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