linux-kernel - Re: [PATCH 3/3] s390/uvdevice: autoload module based on CPU facility

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Message-ID: <20220713111617.0c7dec70@p-imbrenda>
Date:   Wed, 13 Jul 2022 11:16:17 +0200
From:   Claudio Imbrenda <imbrenda@...ux.ibm.com>
To:     Steffen Eiden <seiden@...ux.ibm.com>
Cc:     Heiko Carstens <hca@...ux.ibm.com>,
        Alexander Gordeev <agordeev@...ux.ibm.com>,
        Christian Borntraeger <borntraeger@...ux.ibm.com>,
        Janosch Frank <frankja@...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: [PATCH 3/3] s390/uvdevice: autoload module based on CPU
 facility

On Wed, 13 Jul 2022 10:39:47 +0200
Steffen Eiden <seiden@...ux.ibm.com> wrote:

> On 7/12/22 18:49, Claudio Imbrenda wrote:
> > On Tue, 12 Jul 2022 12:52:20 +0200
> > Steffen Eiden <seiden@...ux.ibm.com> wrote:
> >   
> >> Make sure the uvdevice driver will be automatically loaded when
> >> facility 158 is available.
> >>
> >> Signed-off-by: Steffen Eiden <seiden@...ux.ibm.com>

Reviewed-by: Claudio Imbrenda <imbrenda@...ux.ibm.com>

> >> -module_init(uvio_dev_init);
> >> +module_cpu_feature_match(S390_CPU_FEATURE_UV, uvio_dev_init);  
> > 
> > does this still prevent manual loading when the feature is not present?  
> yes.
> 
> Have a look at the macro definition at 'include/linux/cpufeature.h':
> 
> Use module_cpu_feature_match(feature, module_init_function) to 
> 
> declare that 
> 
> [snip]
> b) the module must not be loaded if CPU feature 'feature' is not present 
> 
>     (not even by manual insmod).

that is what I needed to see :)

> 
> The test 'facility(158)' just moved to cpu_have_feature() in 
> '/arch/s390/kernel/cpufeature.c'.
> >   
> >>   module_exit(uvio_dev_exit);
> >>   
> >>   MODULE_AUTHOR("IBM Corporation");  
> >