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Re: [Xen-users] PCI passthrough partial success

To: Christopher Isip <cmisip@xxxxxxxxx>, xen-users@xxxxxxxxxxxxxxxxxxx
Subject: Re: [Xen-users] PCI passthrough partial success
From: Andy Burns <lists.xensource.com@xxxxxxxxxxxxxx>
Date: Mon, 07 Jul 2008 12:20:35 +0100
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On 02/07/2008 23:27, Christopher Isip wrote:

I have mythbackend running in an Ubuntu-Hardy domU with a Centos 5.1 dom0. Here are the settings that work for me:

After much pulling of hair trying various combinations of pci clots, swiotlb amd pollirq settings, some of which stopped the crashing, but made the dom0 NIC stop working, others stopped the crash but left the domU tuner deaf and/or dumb.

I decided I'd try centos 5.2 dom0 with xen 3.2.0 and I have now got the tuner happily working in the domU, will try two tuners after a few days.

I now don't need any swiotlb settings at all, I have switched from pollirq to noirqdebug on the dom0 as per your settings

I had to a self-build quite a bit ...

  xen (from the xs SRPMS as I'm x86_64)

  dom0 kernel (to enable the PCIID for my NICs for the sky2 driver)

  domU kernel (for the ioremap bug in saa7134 module)

but I'm happy :-)

#It probably wont hurt to increase the domU's scheduling priority, run this in dom0:
xm sched-credit -d Ubuntu-Mythtv -w 512

So far I haven't nee that, I'll see if I do as other domUs get busier

I would suggest having the Mythtv backend not do any transcoding or commflagging. Instead, create slave mythtv backends without tuners and have them do the transcode and commflagging.

I still might do that, also wondering about moving the mysqld to another domU, currently the database is at least on separate xvdb from my recordings disk, so maybe not too bad.

Hope that helps. I am still trying to find ways to optimize the mythbackend domU so If you have any ideas, please let me know.

I came *very* close to giving up and putting mythbackend into dom0 until the paravirt_ops versions of dom0 xen are mainstream - glad I persevered, if you're still having DMA issues I'd say centos5.2+xen3.2 is worth a look.

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