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Date:   Tue, 12 Jul 2022 18:49:24 +0200
From:   Claudio Imbrenda <imbrenda@linux.ibm.com>
To:     Steffen Eiden <seiden@linux.ibm.com>
Cc:     Heiko Carstens <hca@linux.ibm.com>,
        Alexander Gordeev <agordeev@linux.ibm.com>,
        Christian Borntraeger <borntraeger@linux.ibm.com>,
        Janosch Frank <frankja@linux.ibm.com>,
        Vasily Gorbik <gor@linux.ibm.com>, linux-s390@vger.kernel.org,
        linux-kernel@vger.kernel.org, linux-mm@kvack.org, nrb@linux.ibm.com
Subject: Re: [PATCH 3/3] s390/uvdevice: autoload module based on CPU
 facility
Message-ID: <20220712184924.0d80c474@p-imbrenda>
In-Reply-To: <20220712105220.325010-4-seiden@linux.ibm.com>
References: <20220712105220.325010-1-seiden@linux.ibm.com>
        <20220712105220.325010-4-seiden@linux.ibm.com>
Organization: IBM
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On Tue, 12 Jul 2022 12:52:20 +0200
Steffen Eiden <seiden@linux.ibm.com> wrote:

> Make sure the uvdevice driver will be automatically loaded when
> facility 158 is available.
> 
> Signed-off-by: Steffen Eiden <seiden@linux.ibm.com>
> ---
>  arch/s390/include/asm/cpufeature.h | 1 +
>  arch/s390/kernel/cpufeature.c      | 1 +
>  drivers/s390/char/uvdevice.c       | 5 ++---
>  3 files changed, 4 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/s390/include/asm/cpufeature.h b/arch/s390/include/asm/cpufeature.h
> index aa8081dad411..4b17f876ab54 100644
> --- a/arch/s390/include/asm/cpufeature.h
> +++ b/arch/s390/include/asm/cpufeature.h
> @@ -33,6 +33,7 @@ enum {
>  	S390_CPU_FEATURE_NNPA,
>  	S390_CPU_FEATURE_PCI_MIO,
>  	S390_CPU_FEATURE_SIE,
> +	S390_CPU_FEATURE_UV,
>  	MAX_CPU_FEATURES
>  };
>  
> diff --git a/arch/s390/kernel/cpufeature.c b/arch/s390/kernel/cpufeature.c
> index e70b29804db4..0b854d37edcb 100644
> --- a/arch/s390/kernel/cpufeature.c
> +++ b/arch/s390/kernel/cpufeature.c
> @@ -42,6 +42,7 @@ static struct s390_cpu_feature s390_cpu_features[MAX_CPU_FEATURES] = {
>  	[S390_CPU_FEATURE_NNPA]		= {.type = TYPE_HWCAP, .num = HWCAP_NR_NNPA},
>  	[S390_CPU_FEATURE_PCI_MIO]	= {.type = TYPE_HWCAP, .num = HWCAP_NR_PCI_MIO},
>  	[S390_CPU_FEATURE_SIE]		= {.type = TYPE_HWCAP, .num = HWCAP_NR_SIE},
> +	[S390_CPU_FEATURE_UV]		= {.type = TYPE_FACILITY, .num = 158},
>  };
>  
>  /*
> diff --git a/drivers/s390/char/uvdevice.c b/drivers/s390/char/uvdevice.c
> index 66505d7166a6..1d40457c7b10 100644
> --- a/drivers/s390/char/uvdevice.c
> +++ b/drivers/s390/char/uvdevice.c
> @@ -27,6 +27,7 @@
>  #include <linux/stddef.h>
>  #include <linux/vmalloc.h>
>  #include <linux/slab.h>
> +#include <linux/cpufeature.h>
>  
>  #include <asm/uvdevice.h>
>  #include <asm/uv.h>
> @@ -244,12 +245,10 @@ static void __exit uvio_dev_exit(void)
>  
>  static int __init uvio_dev_init(void)
>  {
> -	if (!test_facility(158))
> -		return -ENXIO;
>  	return misc_register(&uvio_dev_miscdev);
>  }
>  
> -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?

>  module_exit(uvio_dev_exit);
>  
>  MODULE_AUTHOR("IBM Corporation");