Re: [dpdk-stable] [PATCH v2] net/virtio-user: fix not working on 32-bit system

["Tan, Jianfeng" <jianfeng.tan@intel.com>]

> -----Original Message-----
> From: Yuanhan Liu [mailto:yuanhan.liu@linux.intel.com]
> Sent: Wednesday, April 19, 2017 1:54 PM
> To: Tan, Jianfeng
> Cc: dev@dpdk.org; olivier.matz@6wind.com; stable@dpdk.org
> Subject: Re: [PATCH v2] net/virtio-user: fix not working on 32-bit system
> 
> On Wed, Apr 19, 2017 at 02:30:33AM +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.
> >
> > In case of virtio-user, we use buf_addr of mbuf to fill the
> > virtqueue desc addr. This is a regression bug. For 32-bit system,
> > the first 4 bytes of mbuf is buf_addr, with following 8 bytes for
> > buf_phyaddr. With below wrong definition, both buf_addr and lower
> > 4 bytes buf_phyaddr are obtained to fill the virtqueue desc.
> >   #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 | 12 +++++++++---
> >  1 file changed, 9 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/net/virtio/virtqueue.h b/drivers/net/virtio/virtqueue.h
> > index f9e3736..2e67460 100644
> > --- a/drivers/net/virtio/virtqueue.h
> > +++ b/drivers/net/virtio/virtqueue.h
> > @@ -69,10 +69,16 @@ struct rte_mbuf;
> >
> >  #ifdef RTE_VIRTIO_USER
> >  /**
> > - * Return the physical address (or virtual address in case of
> > - * virtio-user) of mbuf data buffer.
> > + *
> > + * Return the physical address of mbuf data buffer for virtio pci:
> > + *  on 32-bit system, offset equals 4, return the second four bytes of mbuf;
> > + *  on 64-bit system, offset equals 8, return the second eight bytes of
> mbuf.
> > + * Return the virtual address of mbuf data buffer for virtio-user.
> > + *  on 32-bit system, offset equals 0, return the first four bytes of mbuf;
> > + *  on 64-bit system, offset equals 0, return the first eight bytes of mbuf;
> 
> 
> I've expected it to be plain english, something like following:
> 
>     /*
>      * Return the physical address (or virtual address in case of
>      * virtio-user) of mbuf data buffer.
>      *
>      * The address is firstly casted to the word size (sizeof(uintptr_t))
>      * before casting it to uint64_t. This is to make it work with different
>      * combination of word size (64 bit and 32 bit) and virtio device
>      * (virtio-pci and virtio-user).
>      */
> 
> Okay to you?

Yep, sounds better. Thanks!