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From: | Anthony Liguori |
Subject: | Re: [Qemu-devel] Re: [PATCH 2/3] virtio network device |
Date: | Sat, 08 Dec 2007 15:59:19 -0600 |
User-agent: | Thunderbird 2.0.0.6 (X11/20071022) |
Paul Brook wrote:
virtio makes things a bit trickier though. There's a shared ring queue between the host and guest. The ring queue is lock-less and depends on the ability to atomically increment ring queue indices to be SMP safe. Using a copy-API wouldn't be a problem for QEMU since the host and guest are always running in lock-step. A copy API is actually needed to deal with differing host/guest alignment and endianness.That seems a rather poor design choice, as many architectures don't have an atomic increment instruction. Oh well.
Sorry, I should have been more clear. An atomic increment isn't needed, just an atomic store.
Regards, Anthony Liguori
Paul
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