[Xen-bugs] [Bug 402] Reproducable kernel panic

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http://bugzilla.xensource.com/bugzilla/show_bug.cgi?id=402





------- Additional Comments From ian.pratt@xxxxxxxxxxxx  2005-12-16 05:04 
-------

This issue is fully understood. The 3ware driver is lazy when creating DMA 
mappings and makes them bidirectional. For disk writes when the src buffer is 
above 4GB and has to be bounced this causes a 2nd completely unnecessary memcpy 
after the DMA has occurred, further hurting performance.

On Xen, the extra protection afforded by grant tables means that the 2nd memcpy 
can't write to the buffer as the dom0 only has read-only privilege. As a 
result, 
we kill the domain.

We have a workaround that will supress the fault, but the driver's authors 
could 
really do with fixing it properly if they care about performance.



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