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From: | Avi Kivity |
Subject: | [Qemu-devel] Re: [PATCH 0/4] Block DMA helpers (v2) |
Date: | Sat, 07 Feb 2009 23:16:49 +0200 |
User-agent: | Thunderbird 2.0.0.19 (X11/20090105) |
Anthony Liguori wrote:
This requires that the generic layer be able to tell where a request ends; don't know if that's the case now.Maybe create a sub QEMUSGList from another QEMUSGList. The other option is passing an offset and size to anything that takes a QEMUSGList. You could potentially get smart with how sub SG lists were managed by making them just store an internal offset/size. Although things start to get overly complex at some stage.
Lifetime issues will kill us. I note that something resembling this sort of cleverness is holding up copyless networking -- different parts of an skb have different lifetimes.
But I thought of something simpler: have virtio call virtio-* to inquire whether a ring entry terminates a request. This would also simplify the virtio device emulations somewhat.
-- I have a truly marvellous patch that fixes the bug which this signature is too narrow to contain.
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