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SubjectRe: [PATCH] virtio: fix size computation according to the definition of struct vring_used in vring_size
On 2011年08月27日 17:34, Wang Sheng-Hui wrote:
> On 2011年08月27日 10:49, Wanlong Gao wrote:
>> On Sat, 2011-08-27 at 09:07 +0800, Wang Sheng-Hui wrote:
>>> The patch is against 3.1-rc3.
>>>
>>> struct vring_used has two __u16 fields plus array of struct vring_used_elem.
>>> Current vring_size counts the __u16 fields to 3. Fix it to 2 in the patch.
>>>
>>> Signed-off-by: Wang Sheng-Hui <shhuiw@gmail.com>
>>> ---
>>> include/linux/virtio_ring.h | 2 +-
>>> 1 files changed, 1 insertions(+), 1 deletions(-)
>>>
>>> diff --git a/include/linux/virtio_ring.h b/include/linux/virtio_ring.h
>>> index 4a32cb6..fcda152 100644
>>> --- a/include/linux/virtio_ring.h
>>> +++ b/include/linux/virtio_ring.h
>>> @@ -143,7 +143,7 @@ static inline unsigned vring_size(unsigned int num, unsigned long align)
>>> {
>>> return ((sizeof(struct vring_desc) * num + sizeof(__u16) * (2 + num)
>>> + align - 1) & ~(align - 1))
>>> - + sizeof(__u16) * 3 + sizeof(struct vring_used_elem) * num;
>>> + + sizeof(__u16) * 2 + sizeof(struct vring_used_elem) * num;
>>> }
>>>
>>> /* The following is used with USED_EVENT_IDX and AVAIL_EVENT_IDX */
>>
>> Hi:
>> I'm not deep into it, but I think you can see this:
>> http://marc.info/?l=git-commits-head&m=130687915816130&w=2
>>
>> Thanks
>> -Wanlong Gao
>>
>
> Thanks.
>
> I checked the comments, and think we should patch vring_init
> and vring_size according to the layout description in the comments.
> Right?

New patch generated. Please check it. Thanks,


[PATCH] virtio: modify vring_init and vring_size to take account of the layout containing *_event_idx

The patch is against 3.1-rc3.

Based on the layout description in the comments, take account of
the *_event_idx in functions vring_init and vring_size.

Signed-off-by: Wang Sheng-Hui <shhuiw@gmail.com>
---
include/linux/virtio_ring.h | 6 +++---
1 files changed, 3 insertions(+), 3 deletions(-)

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));
}

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;
}
--
1.7.1

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