diff options
| -rw-r--r-- | virtio-v1.0-wd01-part1-specification.txt | 17 |
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 -------------------------------------- |