Re: [dpdk-dev] [PATCH] virtio: fix used ring address calculation

[Stephen Hemminger <stephen@networkplumber.org>]

On Thu, 24 Sep 2015 07:30:41 +0000
"Xie, Huawei" <huawei.xie@intel.com> wrote:

> On 9/21/2015 11:39 AM, Xie, Huawei wrote:
> vring_size calculation should consider both used_event_idx at the tail
> of avail ring and avail_event_idx at the tail of used ring.
> Will merge those two fixes and send a new patch.
> > used event idx is put at the end of available ring. It isn't taken into account
> > when we calculate the address of used ring. Fortunately, it doesn't introduce
> > the bug with fixed queue number 256 and 4KB alignment.
> >
> > Signed-off-by: hxie5 <huawei.xie@intel.com>
> > ---
> >  drivers/net/virtio/virtio_ring.h | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/net/virtio/virtio_ring.h b/drivers/net/virtio/virtio_ring.h
> > index a16c499..92e430d 100644
> > --- a/drivers/net/virtio/virtio_ring.h
> > +++ b/drivers/net/virtio/virtio_ring.h
> > @@ -145,7 +145,7 @@ vring_init(struct vring *vr, unsigned int num, uint8_t *p,
> >  	vr->avail = (struct vring_avail *) (p +
> >  		num * sizeof(struct vring_desc));
> >  	vr->used = (void *)
> > -		RTE_ALIGN_CEIL((uintptr_t)(&vr->avail->ring[num]), align);
> > +		RTE_ALIGN_CEIL((uintptr_t)(&vr->avail->ring[num + 1]), align);
> >  }
> >  
> >  /*
> 

Why aren't we just using the standard Linux includes for this?
See <linux/virtio_ring.h> and the function vring_init()

Keeping parallel copies of headers is prone to failures.