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From: Paul Brook <paul@codesourcery.com>
Subject: Re: [Qemu-devel] Re: [PATCH 2/3] virtio network device
Date: Wed, 5 Dec 2007 17:44:02 +0000
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To: qemu-devel@nongnu.org
Cc: Anthony Liguori <aliguori@us.ibm.com>, Rusty Russell <rusty@rustcorp.com.au>

> > Actually according to qemu's standard, one should use
> > cpu_physical_memory_write/ cpu_physical_memory_read functions.
> > This is true also for reading the ring values.
>
> Yes, and unfortunately, cpu_physical_memory_{read,write} are copy
> interfaces.  We really don't want that for high speed I/O.

I really don't like doing direct access to guest ram without implementing a 
proper API for zero-copy/scatter-gather access. There was a list thread about 
this not so long ago.

Paul