From mboxrd@z Thu Jan  1 00:00:00 1970
From: "H. Peter Anvin" <hpa@zytor.com>
Subject: Best way to busy-wait for a virtio queue?
Date: Fri, 29 Mar 2013 16:12:37 -0700
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Is there any preferred way to busy-wait on a virtio event?  As in: the
guest doesn't have anything useful to do until something is plopped down
on the virtio queue, but would like to proceed as quickly as possible
after that.  Passing through an interrupt handler seems like unnecessary
overhead.

Right now I have a poll loop looking like (pseudocode):

outw(0, trigger);
while (readl(ring->output pointer) != final output pointer)
	cpu_relax();		/* x86 PAUSE instruction */

... but I have no idea how much sense that makes.


	-hpa