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From: "Tan, Jianfeng" <jianfeng.tan@intel.com>
To: Yuanhan Liu <yuanhan.liu@linux.intel.com>
Cc: "dev@dpdk.org" <dev@dpdk.org>,
	"olivier.matz@6wind.com" <olivier.matz@6wind.com>,
	"stable@dpdk.org" <stable@dpdk.org>
Subject: Re: [dpdk-stable] [PATCH] net/virtio-user: fix not working on 32-bit system
Date: Fri, 14 Apr 2017 05:53:55 +0000	[thread overview]
Message-ID: <ED26CBA2FAD1BF48A8719AEF02201E365119F5FB@SHSMSX103.ccr.corp.intel.com> (raw)
In-Reply-To: <20170414053222.GK7333@yliu-dev.sh.intel.com>



> -----Original Message-----
> From: Yuanhan Liu [mailto:yuanhan.liu@linux.intel.com]
> Sent: Friday, April 14, 2017 1:32 PM
> To: Tan, Jianfeng
> Cc: dev@dpdk.org; olivier.matz@6wind.com; stable@dpdk.org
> Subject: Re: [PATCH] net/virtio-user: fix not working on 32-bit system
> 
> On Thu, Apr 13, 2017 at 02:12:56PM +0000, Jianfeng Tan wrote:
> > virtio-user cannot work on 32-bit system as higher 32-bit of the
> > addr field (64-bit) in the desc is filled with non-zero value
> > which should not happen for a 32-bit system.
> >
> > This is a regression bug. For 32-bit system, the first 4 bytes
> > is the virtual address, with following 8 bytes pointing to
> > physical addr.
> 
> It took me a while to understand that you were trying to say "the first
> 4 bytes __of mbuf__ is ...".

Oops, yes, missed that.

> 
> > With below wrong definition, both virtual address
> > and lower 4 bytes of physical addr are obtained.
> 
> Again, it's not complete. Something like "in the case of virtio-user,
> buf_addr will be used for filling the desc addr, ...". will make it much
> easier to understand.

Yes.

> 
> 
> >   #define VIRTIO_MBUF_ADDR(mb, vq) \
> > 	(*(uint64_t *)((uintptr_t)(mb) + (vq)->offset))
> >
> > Fixes: 25f80d108780 ("net/virtio: fix packet corruption")
> > Cc: stable@dpdk.org
> >
> > Signed-off-by: Jianfeng Tan <jianfeng.tan@intel.com>
> > ---
> >  drivers/net/virtio/virtqueue.h | 3 ++-
> >  1 file changed, 2 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/net/virtio/virtqueue.h b/drivers/net/virtio/virtqueue.h
> > index f9e3736..f43ea70 100644
> > --- a/drivers/net/virtio/virtqueue.h
> > +++ b/drivers/net/virtio/virtqueue.h
> > @@ -72,7 +72,8 @@ struct rte_mbuf;
> >   * Return the physical address (or virtual address in case of
> >   * virtio-user) of mbuf data buffer.
> >   */
> > -#define VIRTIO_MBUF_ADDR(mb, vq) (*(uint64_t *)((uintptr_t)(mb) +
> (vq)->offset))
> > +#define VIRTIO_MBUF_ADDR(mb, vq) \
> > +	((uint64_t)((uintptr_t)(*(void **)((uintptr_t)(mb) + (vq)->offset))))
> 
> The "void **" cast makes it a bit complex (thus hard to read). I think
> following should work?

Yes, uintptr_t can work. I thought void ** is easier to understand, meaning a convert to a pointer which pointing to a pointer. I usually use uintptr_t only for converter from pointer to integer, not the opposite way.

> 
>     (uint64_t(*(uintptr_t *)((uintptr_t)(mb) + (vq)->offset)))
> 
> Besides, it deserves a comment.

Will add comment in next version.

Thanks,
Jianfeng

> 
> 	--yliu
> 
> >  #else
> >  #define VIRTIO_MBUF_ADDR(mb, vq) ((mb)->buf_physaddr)
> >  #endif
> > --
> > 2.7.4

  reply	other threads:[~2017-04-14  5:53 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-04-13 14:12 Jianfeng Tan
2017-04-14  5:32 ` Yuanhan Liu
2017-04-14  5:53   ` Tan, Jianfeng [this message]
2017-04-14  6:20     ` Yuanhan Liu
2017-04-14  6:56       ` Tan, Jianfeng
2017-04-14  7:01         ` Yuanhan Liu
2017-04-14  7:14           ` Tan, Jianfeng
2017-04-19  2:30 ` [dpdk-stable] [PATCH v2] " Jianfeng Tan
2017-04-19  5:53   ` Yuanhan Liu
2017-04-19  6:21     ` Tan, Jianfeng
2017-04-19  6:24       ` Yuanhan Liu

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