linux-kernel - Re: [PATCH] virtio: fix size computation according to the definition of struct vring_used in vring

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Message-ID: <4E58BE42.8030700@gmail.com>
Date:	Sat, 27 Aug 2011 17:52:02 +0800
From:	Wang Sheng-Hui <shhuiw@...il.com>
To:	wanlong.gao@...il.com
CC:	rusty@...tcorp.com.au, mst@...hat.com,
	virtualization@...ts.linux-foundation.org,
	linux-kernel@...r.kernel.org
Subject: Re: [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@...il.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@...il.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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