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

Bruce Richardson bruce.richardson at intel.com
Thu Apr 27 11:25:40 CEST 2017

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.
> Qi Zhang (3):
>   net/i40e: disable vector PMD for i686
>   net/ixgbe: disable vector PMD for i686
>   net/fm10k: disable vector PMD for i686
>  drivers/net/fm10k/Makefile | 2 ++
>  drivers/net/i40e/Makefile  | 2 +-
>  drivers/net/ixgbe/Makefile | 2 +-
>  3 files changed, 4 insertions(+), 2 deletions(-)
> -- 
> 2.9.3

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