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

[Stephen Hemminger <stephen@networkplumber.org>]

On Fri, 25 Sep 2015 15:46:34 +0000
"Xie, Huawei" <huawei.xie@intel.com> wrote:

> On 9/25/2015 5:01 AM, Stephen Hemminger wrote:
> > On Thu, 24 Sep 2015 18:35:37 +0000
> > "Xie, Huawei" <huawei.xie@intel.com> wrote:
> >
> >> On 9/25/2015 12:36 AM, Stephen Hemminger wrote:
> >>> 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.
> >> Agree.
> >> Using standard Linux includes then at least we don't need to redefine
> >> the feature and other related MACRO.
> >> This applies to vhost as well.
> >> For vring, vring_init, we could also reuse the linux implementation
> >> unless we have strong reason to define our own structure.
> >> One reason was to support both FreeBSD and Linux. FreeBSD should have
> >> its own header file. To avoid the case they have different vring
> >> structure or VIRTIO_F_xx macro name, they are redefined here.
> >>
> > The Linux headers for virtio are explictly BSD licensed.
> > You could at least just have a local copy of same code.
> >
> Exactly the same code (if no dependency and no other issue) or copy and
> convert it to DPDK style? By DPDK style, i mean like using RTE_ALIGN macro.

No. keep the Linux code as is. Just copy the headers.
Don't introduce DPDK style.