Re: suggesting wording fixes for virtio-spec 0.9.5

[Laszlo Ersek <lersek@redhat.com>]

On 04/23/13 06:05, Rusty Russell wrote:
> Laszlo Ersek <lersek@redhat.com> 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.
> 

Not sure if it's customary here or if you need it / want it, but anyway

Reviewed-by: Laszlo Ersek <lersek@redhat.com>

(Also I've fixed the OVMF driver; just reposting the patch today with a
better commit message.)

Thanks much!
Laszlo
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