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Date:   Fri, 10 Jun 2022 11:48:40 +0100
From:   Andre Przywara <andre.przywara@arm.com>
To:     Rob Herring <robh@kernel.org>
Cc:     Yoan Picchi <yoan.picchi@arm.com>,
        Giovanni Cabiddu <giovanni.cabiddu@intel.com>,
        Herbert Xu <herbert@gondor.apana.org.au>,
        "David S . Miller" <davem@davemloft.net>, qat-linux@intel.com,
        linux-crypto@vger.kernel.org, linux-kernel@vger.kernel.org,
        Ard Biesheuvel <ardb@kernel.org>
Subject: Re: [PATCH 2/2] Removes the x86 dependency on the QAT drivers
Message-ID: <20220610114840.10db23ea@donnerap.cambridge.arm.com>
In-Reply-To: <20220609213652.GA115440-robh@kernel.org>
References: <20220607165840.66931-1-yoan.picchi@arm.com>
 <20220607165840.66931-3-yoan.picchi@arm.com>
 <20220609213652.GA115440-robh@kernel.org>
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On Thu, 9 Jun 2022 15:36:52 -0600
Rob Herring <robh@kernel.org> wrote:

Hi,

> On Tue, Jun 07, 2022 at 04:58:40PM +0000, Yoan Picchi wrote:
> > This dependency looks outdated. After the previous patch, we have been able
> > to use this driver to encrypt some data and to create working VF on arm64.
> > We have not tested it yet on any big endian machine, hence the new dependency  
> 
> For the subject, use prefixes matching the subsystem (like you did on 
> patch 1).
> 
> The only testing obligation you have is compiling for BE.

So I just compiled for arm64 BE, powerpc BE & LE, and riscv again:
$ file qat_c62xvf.ko
qat_c62xvf.ko: ELF 64-bit MSB relocatable, ARM aarch64, version 1 (SYSV),
BuildID[sha1]=630cc0ee5586c7aeb6e0ab5567ce2f2f7cc46adf, with debug_info,
not stripped
qat_c62xvf.ko: ELF 64-bit MSB relocatable, 64-bit PowerPC or cisco 7500,
version 1 (SYSV), BuildID[sha1]=4090ba181cf95f27108bf3ecde0776f12ef2b636,
not stripped
qat_c62xvf.ko: ELF 64-bit LSB relocatable, 64-bit PowerPC or cisco 7500,
version 1 (SYSV), BuildID[sha1]=2cb0fd09d5bc36c8918fcd061c9f3dac1546cf0d,
not stripped
qat_c62xvf.ko: ELF 64-bit LSB relocatable, UCB RISC-V, version 1 (SYSV),
BuildID[sha1]=bfaa53df7e9aad79d3ab4c05e75ca9169227f6b8, not stripped

All built without errors or warnings, for every of the enabled drivers.

> If kconfig was
> supposed to capture what endianness drivers have been tested or not
> tested with, then lots of drivers are missing the dependency. Kconfig
> depends/select entries should generally be either to prevent compile
> failures (you checked PPC, RiscV, etc.?) or to hide drivers *really*
> specific to a platform. IMO, we should only have !CPU_BIG_ENDIAN if it 
> is known not to work and not easily fixed.

Fair enough, I leave that decision to Giovanni. I have plans to test this
with BE, but getting a BE setup on a server is not trivial, both for
userland and actual booting, so this will take some time. We just didn't
want to block this on some BE concerns.

> Also, with the dependency, no one can test the driver without modifying 
> the kernel and if it does work as-is, then one has to upstream a change 
> and then wait for it to show up in distro kernels. You could mitigate 
> the first part with COMPILE_TEST.

Yeah, that's a good point, we were already bitten by this, the initial
testing was done on a stable distro kernel (v5.4), and it worked fine
already there.

Cheers,
Andre