linux-kernel - Re: [RFC PATCH] s390: Autoload uvdevice module based on CPU feature

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Date:   Wed, 29 Jun 2022 19:14:44 +0200
From:   Heiko Carstens <hca@...ux.ibm.com>
To:     Steffen Eiden <seiden@...ux.ibm.com>
Cc:     Alexander Gordeev <agordeev@...ux.ibm.com>,
        Christian Borntraeger <borntraeger@...ux.ibm.com>,
        Janosch Frank <frankja@...ux.ibm.com>,
        Claudio Imbrenda <imbrenda@...ux.ibm.com>,
        Vasily Gorbik <gor@...ux.ibm.com>, linux-s390@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org, nrb@...ux.ibm.com
Subject: Re: [RFC PATCH] s390: Autoload uvdevice module based on CPU feature

On Wed, Jun 29, 2022 at 05:37:41PM +0200, Steffen Eiden wrote:
> With this patch the uvdevice will be automatically loaded when the
> facility 158 is present. This is accomplished by using
> ``module_cpu_feature_match`` and adding HWCAP_UV
> connected to to facility 158.
> 
> Signed-off-by: Steffen Eiden <seiden@...ux.ibm.com>
> ---
>  arch/s390/include/asm/elf.h  | 2 ++
>  arch/s390/kernel/processor.c | 5 +++++
>  drivers/s390/char/uvdevice.c | 5 ++---
>  3 files changed, 9 insertions(+), 3 deletions(-)

Please split this into two patches: one which adds the hwcap bit, and
one which makes use of it.

Also please make sure the subject contains (nearly) always a
component, which would be "s390/hwcaps: ..." in this case.

> +	/* IBM Secure Execution (Ultravisor) support */
> +	if (test_facility(158)) {
> +		elf_hwcap |= HWCAP_UV;

Just keep the comment short like all other one and take the PoP as
reference. I would have expected something like:
"ultravisor-call (secure execution)"

Besides that, everything looks ok as far as I can tell.