> -----Original Message-----
> From: Yuanhan Liu [mailto:yuanhan....@linux.intel.com]
> Sent: Friday, April 14, 2017 1:32 PM
> To: Tan, Jianfeng
> Cc: dev@dpdk.org; olivier.m...@6wind.com; sta...@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: sta...@dpdk.org
> >
> > Signed-off-by: Jianfeng Tan <jianfeng....@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
