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Re: [Xen-devel] [PATCH] qemu pcnet emulation fixes

Don Fry wrote:
The attached patch to the qemu emulation of the pcnet hardware fixes
several problems.  It will now only read and write a transmit or receive
descriptor once.  It will correctly handle transmitting frames with more
than two fragments.  It will discard oversize frames instead of
corrupting memory.  I have tested all the changes I have made and even
seen an improvement in receive performance from 1.7MB/s to 3.3MB/s.
Your mileage will vary.

Don, the better performance due to the fact that we aren't
reading some descriptors multiple times for no good reason
any more, correct?

The code could be simplified if multi-fragment frames were deleted.  It
appears that both Linux and Windows XP don't use fragmented frames.

I'd suggest we keep this for at least long enough to
validate that the other OSs we want to support don't
use them either.

Thanks very much!


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