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Re: [Xen-devel] Oops when modprobing ivtv outside of dom0

On 5 Jul 2005, at 22:28, David Muench wrote:

I just tried a second time, and it took a few tries of capturing video
to crash it. But even when it didn't crash, all I got was a zero byte
file. I noticed the card was using interrupts (looking at
/proc/interrupts), and things looked ok in dmesg, but no mpeg data.
That time the domU didn't exit on it's own, but was pretty well hung
up (non-responsive other than line feeds on the console). So I tried
to xm destroy it, and that rebooted the entire box.

I think the ivtv driver is probably not calculating dma addresses in the way that xen requires. On native Linux, if you allocate a multi-page chunk of physical memory, you can pass the start address of that buffer to hardware and it can dma the entire buffer given just that address. In Xen, because we give guests 'pseudo-physical' memory, that physical buffer may not be really physically contiguous. So we need drivers to dma_alloc_coherent or pci_alloc_consistent the memory they will use for dma --- we modified those functions to ensure they return suitable contiguous physical memory.

Perhaps the developers may know where to look further.

 -- Keir

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