Hi Oliver, > -----Original Message----- > From: Olivier Matz [mailto:olivier.matz at 6wind.com] > Sent: Tuesday, July 19, 2016 10:00 PM > To: Tan, Jianfeng; dev at dpdk.org; Xie, Huawei; yuanhan.liu at > linux.intel.com > Subject: Re: [PATCH] virtio: fix packet corruption > > Hi, > > On 07/19/2016 03:57 PM, Tan, Jianfeng wrote: > > > > > >> -----Original Message----- > >> From: Olivier Matz [mailto:olivier.matz at 6wind.com] > >> Sent: Tuesday, July 19, 2016 9:11 PM > >> To: Tan, Jianfeng; dev at dpdk.org; Xie, Huawei; > yuanhan.liu at linux.intel.com > >> Subject: Re: [PATCH] virtio: fix packet corruption > >> > >> Hi Jianfeng, > >> > >> On 07/19/2016 03:03 PM, Tan, Jianfeng wrote: > >>> Hi Oliver, > >>> > >>>> -----Original Message----- > >>>> From: Olivier Matz [mailto:olivier.matz at 6wind.com] > >>>> Sent: Tuesday, July 19, 2016 8:32 PM > >>>> To: dev at dpdk.org; Tan, Jianfeng; Xie, Huawei; > >> yuanhan.liu at linux.intel.com > >>>> Subject: [PATCH] virtio: fix packet corruption > >>>> > >>>> The support of virtio-user changed the way the mbuf dma address is > >>>> retrieved, using a physical address in case of virtio-pci and a virtual > >>>> address in case of virtio-user. > >>>> > >>>> This change introduced some possible memory corruption in packets, > >>>> replacing: > >>>> m->buf_physaddr + RTE_PKTMBUF_HEADROOM > >>>> by: > >>>> m->buf_physaddr + m->data_off (through a macro) > >>>> > >>>> This patch fixes this issue, restoring the original behavior. > >>> > >>> Could you be more specific on why we cannot use m->data_off here? > >> > >> There is no guarantee that m->data_off == RTE_PKTMBUF_HEADROOM > here > >> as > >> virtqueue_enqueue_recv_refill() is called on a mbuf that is just > >> allocated with rte_mbuf_raw_alloc(). An alternative would be to set > >> data_off to RTE_PKTMBUF_HEADROOM, but as it's a fix and we are close > to > >> the release, I prefered to restore the initial behavior. > > > > Oh yes, gotcha. > > > > But if we do not set data_off properly, it's still buggy when others consume > these mbufs, right? > > > > This is done later in virtio_recv_pkts*() functions, one the host has > written the data in the mbuf.
Thanks for clarification. Looks good to me. Acked-by: Jianfeng Tan <jianfeng.tan at intel.com>
