Re: [dpdk-dev] [PATCH 0/3 v2] disable vector PMD for i686

[Thomas Monjalon <thomas@monjalon.net>]

27/04/2017 11:25, Bruce Richardson:
> On Thu, Apr 27, 2017 at 03:01:04AM -0400, Qi Zhang wrote:
> > Vector PMD is not designed for i686 orginally, but it still can be active
> > with i686 compile option.
> > Below are observed failure when vPMD is invovled on i686
> > (but may not limited to)
> > 
> > 1) memory overwrite when assign 2 mbuf points to rx return points.
> > _mm_storeu_si128((__m128i *)&rx_pkts[pos+2], mbp2)
> 
> Is this a serious issue that prevents us using the driver? I think it's been
> in the code for quite some time. Can it not be relatively easily fixed for
> 32-bit builds?
> 
> > 
> > 2) rearm_data is not 16 bytes aligned that cause general-protection exception
> > _mm_store_si128((__m128i *)&rx_pkts[0]->rearm_data, rearm0);
> > 
> 
> Good catch. I think this is also an easy fix. My preferred fix is to
> explicitly align the rearm data on a 16-byte boundary. It would add some
> padding to the middle of cacheline0 of the mbuf, but given that we
> explicitly move other data to cacheline1, we will have padding on 32-bit
> anyway, be it in the middle or the end of the mbuf cachelines.
> 
> > So the patch set will exclude Vector PMD from compile with i686 configure.

Please try to fix the drivers instead of turning them off.