diff options
| author | rusty <rusty@0c8fb4dd-22a2-4bb5-bc14-6c75a5f43652> | 2013-08-16 03:19:19 +0000 |
|---|---|---|
| committer | rusty <rusty@0c8fb4dd-22a2-4bb5-bc14-6c75a5f43652> | 2013-08-16 03:19:19 +0000 |
| commit | 2d4fa5d1e24981f838555b08c3ef699299132a52 (patch) | |
| tree | 9753970569ff9d1bf22dfae558ff93a8530aad07 | |
| parent | c000eeef6fb59feaa5c5d89c7ef0268a162035d3 (diff) | |
Make references to "descriptor chains" explicit.
Ported from draft, commit 7a3a665b778039786fade0093df7cc60ebc6cdb1.
Signed-off-by: Rusty Russell <rusty@au1.ibm.com>
git-svn-id: https://tools.oasis-open.org/version-control/svn/virtio@10 0c8fb4dd-22a2-4bb5-bc14-6c75a5f43652
| -rw-r--r-- | virtio-spec.txt | 12 |
1 files changed, 6 insertions, 6 deletions
diff --git a/virtio-spec.txt b/virtio-spec.txt index 6bf1ca8..3b5cb18 100644 --- a/virtio-spec.txt +++ b/virtio-spec.txt @@ -295,10 +295,10 @@ is ignored. 2.1.4.4 The Virtqueue Available Ring ------------------------------------ -The available ring refers to what descriptors we are offering the -device: it refers to the head of a descriptor chain. The “flags” field +The available ring refers to what descriptor chains we are offering the +device: each entry refers to the head of a descriptor chain. The “flags” field is currently 0 or 1: 1 indicating that we do not need an interrupt -when the device consumes a descriptor from the available +when the device consumes a descriptor chain from the available ring. Alternatively, the guest can ask the device to delay interrupts until an entry with an index specified by the “used_event” field is written in the used ring (equivalently, until the idx field in the @@ -493,7 +493,7 @@ above. A naive implementation would do the following: avail->ring[avail->idx % qsz] = head; -However, in general we can add many descriptors before we update +However, in general we can add many descriptor chains before we update the “idx” field (at which point they become visible to the device), so we keep a counter of how many we've added: @@ -503,7 +503,7 @@ device), so we keep a counter of how many we've added: ---------------------------------- Once the index field of the virtqueue is updated, the device will -be able to access the descriptor entries we've created and the +be able to access the descriptor chains we've created and the memory they refer to. This is why a memory barrier is generally used before the index update, to ensure it sees the most up-to-date copy. @@ -1090,7 +1090,7 @@ Discovering what devices are available and their type is bus-dependent. +------------+--------------------+ | 11 | rproc serial | +------------+--------------------+ -| 12 | CAIF | +| 12 | virtio CAIF | +------------+--------------------+ 2.5.1 Network Device |