Re: [PATCH 6/6] virtio ring helper

Avi Kivity
2007-09-23T11:46:21Z

Rusty Russell wrote:
> On Sun, 2007-09-23 at 12:05 +0200, Avi Kivity wrote:
>
>> Rusty Russell wrote:
>>
>>> On Thu, 2007-09-20 at 14:43 +0200, Avi Kivity wrote:
>>>
>>>> 32 bits of page numbers give 44 bits of physical address on x86. That's
>>>> 16TB per guest. Admittedly it's smaller on a VAX.
>>>>
>>> I like to feel that I make these mistakes to ensure others are paying
>>> attention. However, it does mean that I can just put an address in
>>> there and increase the length field to 32 bits. Much rejoicing.
>>>
>>>
>> Why are we sending page numbers anyway? See below.
>>
>
> Perhaps I was unclear. I already changed to a 64-bit address. I
> haven't send out another set of patches because I'm changing to Arnd's
> explicit virtio bus too. Will send out a new set tomorrow at this rate.
>
>

It does say so quite explicitly in the quoted text. Sorry.

>> Where one of the flags is VRING_DESC_INDIRECT, which means that the
>> memory within (address, length) is a bunch of descriptors instead of raw
>> data.
>>
>
> If that's all we wanted, it's fairly easy to do as a future extension
> even if we didn't change it today. My concern was the allocation and
> management of those sg pages; hence my desire for a patch 8)
>

Won't kmalloc()/kfree() suffice? IMO the tradeoff (compared to chaining
with its reduction in ring size, and handling ood) is positive.

I'll try a patch based on the next patchset.

--
error compiling committee.c: too many arguments to function