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authormstsirkin <mstsirkin@0c8fb4dd-22a2-4bb5-bc14-6c75a5f43652>2013-11-10 11:35:04 +0000
committermstsirkin <mstsirkin@0c8fb4dd-22a2-4bb5-bc14-6c75a5f43652>2013-11-10 11:35:04 +0000
commitd0a31aef264b81165af16007b272c2b985edafb4 (patch)
treefb92c232b3306f5f67ba57825f06a297edc1c028
parent30ea341c68cd56b387d2a0013979412f0ca1c855 (diff)
pci: a note on non-transitional devices
Add a note documenting handling legacy drivers for non transitional devices. VIRTIO-34 Accepted Nov 5, 2013 https://lists.oasis-open.org/archives/virtio/201311/msg00031.html Signed-off-by: Michael S. Tsirkin <mst@redhat.com> git-svn-id: https://tools.oasis-open.org/version-control/svn/virtio@89 0c8fb4dd-22a2-4bb5-bc14-6c75a5f43652
-rw-r--r--virtio-v1.0-wd01-part1-specification.txt17
1 files changed, 16 insertions, 1 deletions
diff --git a/virtio-v1.0-wd01-part1-specification.txt b/virtio-v1.0-wd01-part1-specification.txt
index 22aaed5..734bbf4 100644
--- a/virtio-v1.0-wd01-part1-specification.txt
+++ b/virtio-v1.0-wd01-part1-specification.txt
@@ -1167,7 +1167,22 @@ space in BAR0.
Transitional drivers should look for the Virtio PCI
Capabilities on the capability list.
-If there are not present, driver should assume a legacy device.
+If these are not present, driver should assume a legacy device.
+
+Non-transitional drivers should look for the Virtio PCI
+Capabilities on the capability list.
+If these are not present, driver should assume a legacy device,
+and fail gracefully.
+
+Non-transitional devices, on a platform where a legacy driver for
+a legacy device with the same ID might have previously existed,
+must take the following steps to fail gracefully when a legacy
+driver attempts to drive them:
+
+1) Present an I/O BAR in BAR0, and
+2) Respond to a single-byte zero write to offset 18
+ (corresponding to Device Status register in the legacy layout)
+ of BAR0 by presenting zeroes on every BAR and ignoring writes.
2.3.1.3.1.1. Queue Vector Configuration
--------------------------------------