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

[Javier Marcet <jmarcet@xxxxxxxxx>]

On Tue, Sep 18, 2012 at 6:08 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.

No, it is the same machine. It is working as an HTPC, NAS, web and ftp
server right now.
I recently upgraded the CPU to be able to add virtualization as well.

>> 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 :-)

Yes, I guess so. What was clear is that the linux media devs are not
going to help too much with this.

> 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.

So far I have successfully passed through an ASMedia SATA controller
which seemed to work all right. That was with KVM and a Windows 7
guest, though. Trying to pass through the same DVB card (which has two
tuners) didn't exactly work. It shows up as two PCIe devices. On one
of them I can install the driver and gives no errors. On the other one
I can't even install the driver.

Anyhow, I could not tune any channel although I'm not sure the
software provided by Terratec was the best to try.

> 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.

Hmm, all the tests I have done, once it was clear I could not use vdr
since it didn't receive data, has been with 'mplayer -dumpstream' on a
SD channel. I-m pretty certain that it doesn't go over the 2mbps. I
get some data but as mpeg stream it is completely broken.


-- 
Javier Marcet <jmarcet@xxxxxxxxx>

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