summaryrefslogtreecommitdiff
diff options
context:
space:
mode:
-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
--------------------------------------