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DateWed, 03 Jun 2009 19:22:01 +0100
FromDavid <>
SubjectRe: Patch to fix usbmon crash on Opteron
Pete Zaitcev wrote:
> Here's my proposal: forget the clever-by-half tricks and simply use
> transfer_buffer. This should not only fix Opteron, but also future IOMMUs
> that Intel and AMD promise. It may also make usbmon useable on PPC at last.
>
> I think downsides are negligible. The ones I see are:
> - A driver may pass an address of one buffer down as transfer_buffer,
> and entirely different entity mapped for DMA, resulting in misleading
> output of usbmon.
> - Out of tree drivers may crash usbmon if they store garbage in
> transfer_buffer. I went over the tree with a comb and fixed obvious
> bugs, and clarified the documentation in comments.
> - Drivers that use get_user_pages will not be possible to monitor
> - Similar deal is with usb_storage transferring from highmem, but
> it works fine on 64-bit systems, so I think it's not a concern.
>
> I'm adding a sign-off line in case, but in general this is a patch
> for testing. In particular, sisusb is a concern.
>
> David & John, I am quite certain that your Opterons will not crash now,
> but please give it a try, and also you can use this code to produce usbmon
> traces you needed for debugging of other things.
>
> Signed-off-by: Pete Zaitcev <zaitcev@redhat.com>
>
>
Works fine on my system!

Cheers
David


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