[{"id":3682939,"web_url":"http://patchwork.ozlabs.org/comment/3682939/","msgid":"","date":"2026-04-27T20:12:55","subject":"Re: [RFC PATCH v1 9/9] uaccess: Convert small fixed size\n copy_{to/from}_user() to scoped user access","submitter":{"id":92516,"url":"http://patchwork.ozlabs.org/api/people/92516/","name":"Yury Norov","email":"ynorov@nvidia.com"},"content":"On Mon, Apr 27, 2026 at 07:13:50PM +0200, Christophe Leroy (CS GROUP) wrote:\n> copy_{to/from}_user() is a heavy function optimised for copy of large\n> blocs of memory between user and kernel space.\n> \n> When the number of bytes to be copied is known at build time and small,\n> using scoped user access removes the burden of that optimisation.\n> \n> Signed-off-by: Christophe Leroy (CS GROUP) \n> ---\n> include/linux/uaccess.h | 47 +++++++++++++++++++++++++++++++++++++++++\n> 1 file changed, 47 insertions(+)\n> \n> diff --git a/include/linux/uaccess.h b/include/linux/uaccess.h\n> index 33b7d0f5f808..3ac544527af2 100644\n> --- a/include/linux/uaccess.h\n> +++ b/include/linux/uaccess.h\n> @@ -50,6 +50,8 @@\n> #define mask_user_address(src) (src)\n> #endif\n> \n> +#define SMALL_COPY_USER\t\t64\n\nLet's make it L1_CACHE_BYTES, and maybe configurable?","headers":{"Return-Path":"\n ","X-Original-To":["incoming@patchwork.ozlabs.org","linuxppc-dev@lists.ozlabs.org"],"Delivered-To":"patchwork-incoming@legolas.ozlabs.org","Authentication-Results":["legolas.ozlabs.org;\n\tdkim=pass (2048-bit key;\n unprotected) header.d=Nvidia.com header.i=@Nvidia.com header.a=rsa-sha256\n header.s=selector2 header.b=hMJCquiW;\n\tdkim-atps=neutral","legolas.ozlabs.org;\n spf=pass (sender SPF authorized) smtp.mailfrom=lists.ozlabs.org\n (client-ip=112.213.38.117; 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