Received-SPF: pass (google.com: domain of linux-kernel+bounces-58741-linux.lists.archive=gmail.com@vger.kernel.org designates 2604:1380:45e3:2400::1 as permitted sender) client-ip=2604:1380:45e3:2400::1;
Date: Thu, 8 Feb 2024 13:52:53 -0800
From: Dan Williams <dan.j.williams@intel.com>
To: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>, Dan Williams
	<dan.j.williams@intel.com>, Arnd Bergmann <arnd@arndb.de>, Dave Chinner
	<david@fromorbit.com>
CC: <linux-kernel@vger.kernel.org>, Mathieu Desnoyers
	<mathieu.desnoyers@efficios.com>, Andrew Morton <akpm@linux-foundation.org>,
	Linus Torvalds <torvalds@linux-foundation.org>, Vishal Verma
	<vishal.l.verma@intel.com>, Dave Jiang <dave.jiang@intel.com>, Matthew Wilcox
	<willy@infradead.org>, Russell King <linux@armlinux.org.uk>,
	<linux-arch@vger.kernel.org>, <linux-cxl@vger.kernel.org>,
	<linux-fsdevel@vger.kernel.org>, <linux-mm@kvack.org>,
	<linux-xfs@vger.kernel.org>, <dm-devel@lists.linux.dev>,
	<nvdimm@lists.linux.dev>, <linux-s390@vger.kernel.org>
Subject: RE: [PATCH v4 08/12] dax: Fix incorrect list of data cache aliasing
 architectures
Message-ID: <65c54d352f294_afa42942c@dwillia2-xfh.jf.intel.com.notmuch>
References: <20240208184913.484340-1-mathieu.desnoyers@efficios.com>
 <20240208184913.484340-9-mathieu.desnoyers@efficios.com>
Content-Type: text/plain; charset="us-ascii"
Content-Disposition: inline
In-Reply-To: <20240208184913.484340-9-mathieu.desnoyers@efficios.com>
Precedence: bulk
MIME-Version: 1.0
X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1
X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?TRTQJp9dLkjQJerZNm4/RtTBJHdEfAXhWR2Hb3TI3VfpumjqWD97aJiEuo5J?=
 =?us-ascii?Q?H0ql8fGQHC1POYDuz1d+ZMtEVCwIcUlG+OUSwdxiQPTy2h9wW8cM6m9/md2P?=
 =?us-ascii?Q?x+A0giOa4mSQzg3Av4CRbzBcSf39HNxTTYaIE90im/ESS2a4ddwiiXPZGHjz?=
 =?us-ascii?Q?BRmA9k/48PNHi322CrAF7scJ1CiG2NR3qzMIr/EBuTfuOYMwCO2QXxV//l46?=
 =?us-ascii?Q?gPS9l7HzYktmkZQumTEBOZnn+eDCr0DdOeNZ2Cgvf5JfQinepW78LrOiK4IB?=
 =?us-ascii?Q?9bi8m20pXe7j74nJmMbUMYfgnfobCrfwXVU+wMiqTMPgOmlzxG0Wt1rnyG4d?=
 =?us-ascii?Q?/06IGHLLha315cqQKDytGKz+iJWc1JXHucEzXOHmHgct6+h1lKdYIvWo3j9f?=
 =?us-ascii?Q?Ny/zwUemEUynDQvu2xckfWT1E+4tA+3kxwSfFqiW9ppPA2ndMlX4vpz2c4la?=
 =?us-ascii?Q?fynTB+Fq7RA47c0wa5e1M5xSdbhXd8qiPzLNI3eS6OGZGHfbZ3fqMOf3Byf6?=
 =?us-ascii?Q?1oZD0BYJtdQwPAgOBkCRemb7d39bqpi0HUQvKhBg8CdqFE62apRbmkN5mvjR?=
 =?us-ascii?Q?ezzZMOKyp8yoXPL9PPZzv1g2DNO49XyKvucM0ml+uX5oMlc9h44wB5mMG3Bu?=
 =?us-ascii?Q?r2fA1fMHKTAATKoADv+uS4o+aJlPY0sPI+rd8DQff7ULJWSnNVA8RTdf0P/d?=
 =?us-ascii?Q?Uq7/q7WX5Pfs5hG4l/5jXfXP+Xm0qJbUWI5kbo7h09071SY78/8DzHO7vxAp?=
 =?us-ascii?Q?uRjuSe1wNZktngvLw4SwpSOTnIE2R5QQGxKYRBea1ss6/8dTQTggTo9Zyhv6?=
 =?us-ascii?Q?IUrcS5Vzz51hM90CkTvrs0Je/QUKfkX94UX588oWDJdVa5rS3bbk06wWJeQx?=
 =?us-ascii?Q?rNQSlvl/J5yO8UtBFd0vjIdnW7jzaUFRZiOyz4o5E9XzdZcEEk3s5YLVSik0?=
 =?us-ascii?Q?2sbQAnBvYLAM2TvPG+17kfZysoxfh6SXUipkW76i9IQX24U6ZU8DRL7W/sAh?=
 =?us-ascii?Q?iy+rg+Hu8bnVbQzHA0qPIC27bd3WUXDc86FZcu+qLVW05fplf6QyPf6gnr9f?=
 =?us-ascii?Q?zDyhJnQpgY/z5h5l2ud1AzrkYW3JNaFofgPoSctKyTvhqy3w9K3HD/j9rs6C?=
 =?us-ascii?Q?McviKop0U28Q4DR7OFHfoZH4qEL60+f3Qlb7/GrmoWRAuMuFXrjdrHDoatlq?=
 =?us-ascii?Q?Ap6dGz9IYJsTxRV9L6sq4v6v4miZIBxeVTCCjTVg2089Nh0swfMPeW8F4yzn?=
 =?us-ascii?Q?nOJAXTI2sHNmiR4vZ8oamKSae1Rdnoy+HohooQAsGvaHh3hCjln43xB6vZ5+?=
 =?us-ascii?Q?adsnn3JVwNiJBrVkwIrAxLEsQa2n/aSufiYyqDdhqw4zRCGhvVFxgoFSSrlC?=
 =?us-ascii?Q?O8J82wiHM1So2popYSTo1ss4wWzAfVeAciAW0ADs6/rGRz0CxBJNPLpdaiDa?=
 =?us-ascii?Q?Y0LJjsN/oWJVKECvW8T/ZgH4tn1Vu4xg6ZUNGCsc4fSrL+n0Gi4h/HvTcNkW?=
 =?us-ascii?Q?kniMc9hTLD/4JeG+wEPRQnSxXFjxoYfUEWmc7HGDGeR2bIlAUfNwgC7vR3nv?=
 =?us-ascii?Q?pPzB03vW6uWJ3fZ6XMFOvOtrABbwskTViOK2ygpP3KJ5+cGtm4ZJpQF/EX1O?=
 =?us-ascii?Q?Rg=3D=3D?=
X-MS-Exchange-CrossTenant-Network-Message-Id: b54e0b2f-48c1-435e-2394-08dc28f04eb7
X-MS-Exchange-CrossTenant-AuthSource: PH8PR11MB8107.namprd11.prod.outlook.com
X-MS-Exchange-CrossTenant-AuthAs: Internal
X-MS-Exchange-CrossTenant-OriginalArrivalTime: 08 Feb 2024 21:52:55.8912
 (UTC)
X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted
X-MS-Exchange-CrossTenant-Id: 46c98d88-e344-4ed4-8496-4ed7712e255d
X-MS-Exchange-CrossTenant-MailboxType: HOSTED
X-MS-Exchange-CrossTenant-UserPrincipalName: m5CBcdfuyGTkVlrgYxpitsEGE/PWC1OmbgZvfrh2Dyq1kwRiSo8b7RGjdSDKtE7vZTnAELw0OnvYWpqKxd/VPZ1zcfG32aZKflVQXNQX+lU=
X-MS-Exchange-Transport-CrossTenantHeadersStamped: PH7PR11MB7513
X-OriginatorOrg: intel.com

Mathieu Desnoyers wrote:
> commit d92576f1167c ("dax: does not work correctly with virtual aliasing caches")
> prevents DAX from building on architectures with virtually aliased
> dcache with:
> 
>   depends on !(ARM || MIPS || SPARC)
> 
> This check is too broad (e.g. recent ARMv7 don't have virtually aliased
> dcaches), and also misses many other architectures with virtually
> aliased data cache.
> 
> This is a regression introduced in the v4.0 Linux kernel where the
> dax mount option is removed for 32-bit ARMv7 boards which have no data
> cache aliasing, and therefore should work fine with FS_DAX.
> 
> This was turned into the following check in alloc_dax() by a preparatory
> change:
> 
>         if (ops && (IS_ENABLED(CONFIG_ARM) ||
>             IS_ENABLED(CONFIG_MIPS) ||
>             IS_ENABLED(CONFIG_SPARC)))
>                 return NULL;
> 
> Use cpu_dcache_is_aliasing() instead to figure out whether the environment
> has aliasing data caches.
> 
> Fixes: d92576f1167c ("dax: does not work correctly with virtual aliasing caches")
> Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: Linus Torvalds <torvalds@linux-foundation.org>
> Cc: Dan Williams <dan.j.williams@intel.com>
> Cc: Vishal Verma <vishal.l.verma@intel.com>
> Cc: Dave Jiang <dave.jiang@intel.com>
> Cc: Matthew Wilcox <willy@infradead.org>
> Cc: Arnd Bergmann <arnd@arndb.de>
> Cc: Russell King <linux@armlinux.org.uk>
> Cc: linux-arch@vger.kernel.org
> Cc: linux-cxl@vger.kernel.org
> Cc: linux-fsdevel@vger.kernel.org
> Cc: linux-mm@kvack.org
> Cc: linux-xfs@vger.kernel.org
> Cc: dm-devel@lists.linux.dev
> Cc: nvdimm@lists.linux.dev
> ---
>  drivers/dax/super.c | 5 ++---
>  1 file changed, 2 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/dax/super.c b/drivers/dax/super.c
> index ce5bffa86bba..a21a7c262382 100644
> --- a/drivers/dax/super.c
> +++ b/drivers/dax/super.c
> @@ -13,6 +13,7 @@
>  #include <linux/uio.h>
>  #include <linux/dax.h>
>  #include <linux/fs.h>
> +#include <linux/cacheinfo.h>
>  #include "dax-private.h"
>  
>  /**
> @@ -455,9 +456,7 @@ struct dax_device *alloc_dax(void *private, const struct dax_operations *ops)
>  	 * except for device-dax (NULL operations pointer), which does
>  	 * not use aliased mappings from the kernel.
>  	 */
> -	if (ops && (IS_ENABLED(CONFIG_ARM) ||
> -	    IS_ENABLED(CONFIG_MIPS) ||
> -	    IS_ENABLED(CONFIG_SPARC)))
> +	if (ops && cpu_dcache_is_aliasing())
>  		return ERR_PTR(-EOPNOTSUPP);

Looks good,

Reviewed-by: Dan Williams <dan.j.williams@intel.com>