linux-kernel - Re: [PATCH] net/chelsio/libcxgb: Add __percpu annotations to libcxgb

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Message-ID: <20240731093516.GR1967603@kernel.org>
Date: Wed, 31 Jul 2024 10:35:16 +0100
From: Simon Horman <horms@...nel.org>
To: Uros Bizjak <ubizjak@...il.com>
Cc: netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>
Subject: Re: [PATCH] net/chelsio/libcxgb: Add __percpu annotations to
 libcxgb_ppm.c

On Tue, Jul 30, 2024 at 02:58:19PM +0200, Uros Bizjak wrote:
> Compiling libcxgb_ppm.c results in several sparse warnings:
> 
> libcxgb_ppm.c:368:15: warning: incorrect type in assignment (different address spaces)
> libcxgb_ppm.c:368:15:    expected struct cxgbi_ppm_pool *pools
> libcxgb_ppm.c:368:15:    got void [noderef] __percpu *_res
> libcxgb_ppm.c:374:48: warning: incorrect type in initializer (different address spaces)
> libcxgb_ppm.c:374:48:    expected void const [noderef] __percpu *__vpp_verify
> libcxgb_ppm.c:374:48:    got struct cxgbi_ppm_pool *
> libcxgb_ppm.c:484:19: warning: incorrect type in assignment (different address spaces)
> libcxgb_ppm.c:484:19:    expected struct cxgbi_ppm_pool [noderef] __percpu *pool
> libcxgb_ppm.c:484:19:    got struct cxgbi_ppm_pool *[assigned] pool
> libcxgb_ppm.c:511:21: warning: incorrect type in argument 1 (different address spaces)
> libcxgb_ppm.c:511:21:    expected void [noderef] __percpu *__pdata
> libcxgb_ppm.c:511:21:    got struct cxgbi_ppm_pool *[assigned] pool
> 
> Add __percpu annotation to *pools and *pool percpu pointers and to
> ppm_alloc_cpu_pool() function that returns percpu pointer to fix
> these warnings.
> 
> Compile tested only, but there is no difference in the resulting object file.
> 
> Signed-off-by: Uros Bizjak <ubizjak@...il.com>
> Cc: "David S. Miller" <davem@...emloft.net>
> Cc: Eric Dumazet <edumazet@...gle.com>
> Cc: Jakub Kicinski <kuba@...nel.org>
> Cc: Paolo Abeni <pabeni@...hat.com>
> ---
>  drivers/net/ethernet/chelsio/libcxgb/libcxgb_ppm.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/net/ethernet/chelsio/libcxgb/libcxgb_ppm.c b/drivers/net/ethernet/chelsio/libcxgb/libcxgb_ppm.c
> index 854d87e1125c..01d776113500 100644
> --- a/drivers/net/ethernet/chelsio/libcxgb/libcxgb_ppm.c
> +++ b/drivers/net/ethernet/chelsio/libcxgb/libcxgb_ppm.c
> @@ -342,10 +342,10 @@ int cxgbi_ppm_release(struct cxgbi_ppm *ppm)
>  }
>  EXPORT_SYMBOL(cxgbi_ppm_release);
>  
> -static struct cxgbi_ppm_pool *ppm_alloc_cpu_pool(unsigned int *total,
> -						 unsigned int *pcpu_ppmax)
> +static struct cxgbi_ppm_pool __percpu *ppm_alloc_cpu_pool(unsigned int *total,
> +							  unsigned int *pcpu_ppmax)

Let's keep to less than 80 columns wide, as is still preferred for
Networking code. Perhaps in this case:

static struct cxgbi_ppm_pool __percpu *
ppm_alloc_cpu_pool(unsigned int *total, unsigned int *pcpu_ppmax)

Also, I do observe that this is an old driver, so the value
of cleaning it is perhaps limited.

But the above aside, this looks good to me.

>  {
> -	struct cxgbi_ppm_pool *pools;
> +	struct cxgbi_ppm_pool __percpu *pools;
>  	unsigned int ppmax = (*total) / num_possible_cpus();
>  	unsigned int max = (PCPU_MIN_UNIT_SIZE - sizeof(*pools)) << 3;
>  	unsigned int bmap;