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[Qemu-devel] Re: [PATCH] e1000: clear EOP for multi-buffer descriptors
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From: |
Juan Quintela |
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Subject: |
[Qemu-devel] Re: [PATCH] e1000: clear EOP for multi-buffer descriptors |
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Date: |
Mon, 07 Feb 2011 13:32:53 +0100 |
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User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/23.2 (gnu/linux) |
"Michael S. Tsirkin" <address@hidden> wrote:
> The e1000 spec says: if software statically allocates
> buffers, and uses memory read to check for completed descriptors, it
> simply has to zero the status byte in the descriptor to make it ready
> for reuse by hardware. This is not a hardware requirement (moving the
> hardware tail pointer is), but is necessary for performing an in–memory
> scan.
>
> Thus the guest does not have to clear the status byte. In case it
> doesn't we need to clear EOP for all descriptors
> except the last. While I don't know of any such guests,
> it's probably a good idea to stick to the spec.
>
> Signed-off-by: Michael S. Tsirkin <address@hidden>
> Reported-by: Juan Quintela <address@hidden>
reviewed-by: Juan Quintela <address@hidden>