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Date:   Mon, 14 Sep 2020 18:12:34 +0200
From:   Jesper Dangaard Brouer <brouer@redhat.com>
To:     Will Deacon <will@kernel.org>
Cc:     brouer@redhat.com, Ilias Apalodimas <ilias.apalodimas@linaro.org>,
        bpf@vger.kernel.org, ardb@kernel.org, naresh.kamboju@linaro.org,
        Jean-Philippe Brucker <jean-philippe@linaro.org>,
        Yauheni Kaliuta <yauheni.kaliuta@redhat.com>,
        Daniel Borkmann <daniel@iogearbox.net>,
        Alexei Starovoitov <ast@kernel.org>,
        Zi Shen Lim <zlim.lnx@gmail.com>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Martin KaFai Lau <kafai@fb.com>,
        Song Liu <songliubraving@fb.com>, Yonghong Song <yhs@fb.com>,
        Andrii Nakryiko <andriin@fb.com>,
        John Fastabend <john.fastabend@gmail.com>,
        KP Singh <kpsingh@chromium.org>,
        "David S. Miller" <davem@davemloft.net>,
        Jakub Kicinski <kuba@kernel.org>,
        Jesper Dangaard Brouer <hawk@kernel.org>,
        netdev@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
        linux-kernel@vger.kernel.org,
        Anders Roxell <anders.roxell@linaro.org>
Subject: Re: [PATCH] arm64: bpf: Fix branch offset in JIT
Message-ID: <20200914181234.0f1df8ba@carbon>
In-Reply-To: <20200914140114.GG24441@willie-the-truck>
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        <20200914123504.GA124316@apalos.home>
        <20200914132350.GA126552@apalos.home>
        <20200914140114.GG24441@willie-the-truck>
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On Mon, 14 Sep 2020 15:01:15 +0100 Will Deacon <will@kernel.org> wrote:

> Hi Ilias,
> 
> On Mon, Sep 14, 2020 at 04:23:50PM +0300, Ilias Apalodimas wrote:
> > On Mon, Sep 14, 2020 at 03:35:04PM +0300, Ilias Apalodimas wrote:  
> > > On Mon, Sep 14, 2020 at 01:20:43PM +0100, Will Deacon wrote:  
> > > > On Mon, Sep 14, 2020 at 11:36:21AM +0300, Ilias Apalodimas wrote:  
> > > > > Running the eBPF test_verifier leads to random errors looking like this:  
> 
> [...]
> > >   
> > Any suggestion on any Fixes I should apply? The original code was 'correct' and
> > broke only when bounded loops and their self-tests were introduced.  
> 
> Ouch, that's pretty bad as it means nobody is regression testing BPF on
> arm64 with mainline. Damn.

Yes, it unfortunately seems that upstream is lacking BPF regression
testing for ARM64 :-(

This bug surfaced when Red Hat QA tested our kernel backports, on
different archs.

-- 
Best regards,
  Jesper Dangaard Brouer
  MSc.CS, Principal Kernel Engineer at Red Hat
  LinkedIn: http://www.linkedin.com/in/brouer