From 69fbbac976180a38519d2319c7927ec09b746119 Mon Sep 17 00:00:00 2001
From: rusty <rusty@0c8fb4dd-22a2-4bb5-bc14-6c75a5f43652>
Date: Fri, 16 Aug 2013 03:20:05 +0000
Subject: 2.6 Reserved Feature Bits: document bit 30 as used by qemu.

Partial port of draft commit 835628846cc04efe660e505552d06eb945277d3b.

Signed-off-by: Rusty Russell <rusty@au1.ibm.com>

git-svn-id: https://tools.oasis-open.org/version-control/svn/virtio@13 0c8fb4dd-22a2-4bb5-bc14-6c75a5f43652
---
 virtio-spec.txt | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/virtio-spec.txt b/virtio-spec.txt
index f7c80ec..d762461 100644
--- a/virtio-spec.txt
+++ b/virtio-spec.txt
@@ -2502,6 +2502,10 @@ Currently there are four device-independent feature bits defined:
   ignore the avail_event field; the flags field is used
 
 
+In addition, bit 30 is used by qemu's implementation to check for experimental
+early versions of virtio which did not perform correct feature negotiation,
+and should not be used.
+
 2.7 virtio_ring.h
 =================
 
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