netdev - Re: [net-next v5 01/15] virtchnl: Extend AVF ops

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Message-ID: <20200911080822.333f79b7@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com>
Date:   Fri, 11 Sep 2020 08:08:22 -0700
From:   Jakub Kicinski <kuba@...nel.org>
To:     "Brady, Alan" <alan.brady@...el.com>
Cc:     "Nguyen, Anthony L" <anthony.l.nguyen@...el.com>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "Michael, Alice" <alice.michael@...el.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "nhorman@...hat.com" <nhorman@...hat.com>,
        "sassmann@...hat.com" <sassmann@...hat.com>,
        "Kirsher, Jeffrey T" <jeffrey.t.kirsher@...el.com>,
        "Burra, Phani R" <phani.r.burra@...el.com>,
        "Hay, Joshua A" <joshua.a.hay@...el.com>,
        "Chittim, Madhu" <madhu.chittim@...el.com>,
        "Linga, Pavan Kumar" <pavan.kumar.linga@...el.com>,
        "Skidmore, Donald C" <donald.c.skidmore@...el.com>,
        "Brandeburg, Jesse" <jesse.brandeburg@...el.com>,
        "Samudrala, Sridhar" <sridhar.samudrala@...el.com>
Subject: Re: [net-next v5 01/15] virtchnl: Extend AVF ops

On Thu, 10 Sep 2020 21:06:05 +0000 Brady, Alan wrote:
> > It seems like these are triggering on old messages too, curious why this wasn't
> > caught sooner.  Will fix, thanks.
> > 
> I managed to get a 32-bit build environment setup and found that we
> do indeed have alignment issues there on 32 bit systems for some of
> the new ops we added with the series.  However, I think I'm still
> missing something as it looks like you have errors triggering on much
> more than I found and I'm suspecting there might be a compile option
> I'm missing or perhaps my GCC version is older than yours.  E.g., I
> found issues in virtchnl_txq_info_v2, virtchnl_rxq_info_v2,
> virtchnl_config_rx_queues, and virtchnl_rss_hash.  It appears you
> have compile issues in virtchnl_get_capabilities (among others)
> however which did not trigger on mine.  Manual inspection indicates
> that it _should_ be triggering a failure and that your setup is more
> correct than mine.  I'm guessing some extra padding is getting
> included in some places and causing a false positive on the other
> alignment issues.  Are there any hints you can provide me that might
> help me more accurately reproduce this?

Hm. I build like this:

make CC="ccache gcc" O=build32/ ARCH=i386 allmodconfig
make CC="ccache gcc" O=build32/ ARCH=i386 -j 64 W=1 C=1

My GCC is:
Target: x86_64-pc-linux-gnu
Configured with: ../gcc-10.1.0/configure --enable-languages=c,c++
Thread model: posix
Supported LTO compression algorithms: zlib zstd
gcc version 10.1.0 (GCC)