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Re: [Xen-users] Yes, it does! (Does the amount of main memory influence

To: Stephan Austermühle <au@xxxxxxx>
Subject: Re: [Xen-users] Yes, it does! (Does the amount of main memory influence PCI pass through (DMA) capability?)
From: Jeroen Groenewegen van der Weyden <groen692@xxxxxxxxx>
Date: Mon, 10 Aug 2009 10:37:47 +0200
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I seen the same problem with motherboard DQ45CB with 4 gig and pci pass-through enabled. The system just freezes at start up. when reducing the memory to 2 gig he system boots ok and is working fine, including the pci pass-through.

Opensuse 11.1
xen 3.3.1_18546



Stephan Austermühle wrote:
Hi all,

quoting myself:

after solving a lot of problems with my DVB-S card it finally ran fine in my domU (3.3.2-rc2, 64 bit, Debian Lenny kernel 2.6.26-2, 64 bit). However, my memory upgrade kit arrived so I upgraded main memory from 16 gbytes to 32 gbytes. Since then I have a lot of strange issues which are all looking like no data is transfered from the DVB-S card to the domU. When running the tool "dvbtraffic" I get the following message on the console:

	cx8802_start_dma() Failed. Unsupported value in .mpeg (0x00000001)

Does the amount of main memory influence the capability to use DMA transfers?

I don't see any other error message (xm dmesg, xm log, dom0 logs, domU logs). Do I have a chance to get more debug information on this?

Meanwhile I have cross-checked this problem and can reproduce the problem with a standard PC: The above mentioned configuration runs fine with PCI pass through with just 2 gbytes of main memory but as soon as the system has 4 gbytes DVB-S scan does not find data anymore. For me this looks like a DMA problem.

As describe above I am facing the same problem with my server but with a 16 to 32 gbytes upgrade.

Does anybody know the technical background for this? Even better: What needs to be done to fix this problem?

Kind regards,


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