Laszlo Ersek <lersek@xxxxxxxxxx> writes: > Hi, > > (I'm not subscribed to either list,) > > using the word "descriptor" is misleading in the following sections: Yes, I like the use of 'descriptor chains'. This is a definite improvement. Here's the diff I ended up with (massaged to minimize it). Thanks! Rusty. --- virtio-spec.txt-old 2013-04-23 13:22:21.339158214 +0930 +++ virtio-spec.txt 2013-04-23 13:34:14.055176464 +0930 @@ -482,10 +482,10 @@ 2.3.4 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” +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 +interrupt 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, @@ -671,16 +671,16 @@ avail->ring[avail->idx % qsz] = head; -However, in general we can add many descriptors 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: +However, in general we can add many separate 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: avail->ring[(avail->idx + added++) % qsz] = head; 2.4.1.3 Updating The Index Field Once the idx 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 idx update, to ensure it sees the most up-to-date copy. _______________________________________________ Virtualization mailing list Virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linuxfoundation.org/mailman/listinfo/virtualization
