On 2011年08月29日 10:53, Rusty Russell wrote:
> On Sat, 27 Aug 2011 17:52:02 +0800, Wang Sheng-Hui <shhuiw@xxxxxxxxx> wrote:
>> On 2011年08月27日 17:34, Wang Sheng-Hui wrote:
>> diff --git a/include/linux/virtio_ring.h b/include/linux/virtio_ring.h
>> index 4a32cb6..300af76 100644
>> --- a/include/linux/virtio_ring.h
>> +++ b/include/linux/virtio_ring.h
>> @@ -135,13 +135,13 @@ static inline void vring_init(struct vring *vr, unsigned int num, void *p,
>> vr->num = num;
>> vr->desc = p;
>> vr->avail = p + num*sizeof(struct vring_desc);
>> - vr->used = (void *)(((unsigned long)&vr->avail->ring[num] + align-1)
>> - & ~(align - 1));
>> + vr->used = (void *)(((unsigned long)&vr->avail->ring[num] + 16
>> + + align-1) & ~(align - 1));
>> }
>
> This + 16 should be + sizeof(__u16), right? It's just the
> used_event_idx which has been added:
Yes.
>
> * __u16 available[num];
> * __u16 used_event_idx;
> *
> * // Padding to the next align boundary.
> * char pad[];
> *
> * [USED]
>
>> static inline unsigned vring_size(unsigned int num, unsigned long align)
>> {
>> - return ((sizeof(struct vring_desc) * num + sizeof(__u16) * (2 + num)
>> + return ((sizeof(struct vring_desc) * num + sizeof(__u16) * (3 + num)
>> + align - 1) & ~(align - 1))
>> + sizeof(__u16) * 3 + sizeof(struct vring_used_elem) * num;
>
> This is correct.
>
> And, yes, since align is always 4096, it's currently just a cleanup, but
> it makes things much less confusing!
>
> Thanks,
> Rusty.
_______________________________________________
Virtualization mailing list
Virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx
https://lists.linux-foundation.org/mailman/listinfo/virtualization
