Re: [dpdk-dev] [PATCH] virtio: fix allocating virtnet_rx not mem aligned

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

> -----Original Message-----
> From: Yuanhan Liu [mailto:yuanhan.liu@linux.intel.com]
> Sent: Monday, June 13, 2016 5:52 PM
> To: Tan, Jianfeng
> Cc: dev@dpdk.org; Xie, Huawei
> Subject: Re: [dpdk-dev] [PATCH] virtio: fix allocating virtnet_rx not mem
> aligned
> 
> On Mon, Jun 13, 2016 at 05:21:01PM +0800, Yuanhan Liu wrote:
> > On Sun, Jun 12, 2016 at 02:29:42PM +0000, Jianfeng Tan wrote:
> > > Compile DPDK with clang, below line in virtio_rxtx.c could be
> > > optimized with four "VMOVAPS ymm, m256".
> > >   memset(&rxvq->fake_mbuf, 0, sizeof(rxvq->fake_mbuf));
> > >
> > > This instruction requires memory address is 32-byte aligned.
> > > Or, it leads to segfault.
> >
> > That looks like a dangerous optimization to me. If that's the case,
> > doesn't it mean we have to make sure the address is always aligned
> > properly while calling memset?
> 
> Above is just a side note. Anyway, I think making sure vq is cache
> aligned is good here. So, I will apply it. BTW, do you mind if I
> squash your 2 fixes into Huawei's Rx/Tx split commit? His commit is
> not pushed to upstream yet, therefore I can still do rebase: I'm
> thinking it's better to have one working commit other than one broken
> commit followed with several fixing commits. And of course, I will
> mention your contribution in the commit log.

Not a problem from my side. But Huawei seems to have concerns on this fix. You can do that for the other fix firstly.

Thanks,
Jianfeng

> 
> 	--yliu