From: Yury Norov <ynorov@nvidia.com>
To: "Christophe Leroy (CS GROUP)" <chleroy@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
David Laight <david.laight.linux@gmail.com>,
Thomas Gleixner <tglx@linutronix.de>,
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Subject: Re: [RFC PATCH v1 9/9] uaccess: Convert small fixed size copy_{to/from}_user() to scoped user access
Date: Mon, 27 Apr 2026 16:12:55 -0400 [thread overview]
Message-ID: <ae_DR6NYwy05mhAe@yury> (raw)
In-Reply-To: <8780eb2ef80575931a339e5225bc80eb13e9be6c.1777306795.git.chleroy@kernel.org>
On Mon, Apr 27, 2026 at 07:13:50PM +0200, Christophe Leroy (CS GROUP) wrote:
> copy_{to/from}_user() is a heavy function optimised for copy of large
> blocs of memory between user and kernel space.
>
> When the number of bytes to be copied is known at build time and small,
> using scoped user access removes the burden of that optimisation.
>
> Signed-off-by: Christophe Leroy (CS GROUP) <chleroy@kernel.org>
> ---
> include/linux/uaccess.h | 47 +++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 47 insertions(+)
>
> diff --git a/include/linux/uaccess.h b/include/linux/uaccess.h
> index 33b7d0f5f808..3ac544527af2 100644
> --- a/include/linux/uaccess.h
> +++ b/include/linux/uaccess.h
> @@ -50,6 +50,8 @@
> #define mask_user_address(src) (src)
> #endif
>
> +#define SMALL_COPY_USER 64
Let's make it L1_CACHE_BYTES, and maybe configurable?
next prev parent reply other threads:[~2026-04-27 20:13 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-04-27 17:13 [RFC PATCH v1 0/9] uaccess: Convert small fixed size copy_{to/from}_user() to scoped user access Christophe Leroy (CS GROUP)
2026-04-27 17:13 ` [RFC PATCH v1 1/9] uaccess: Split check_zeroed_user() out of usercopy.c Christophe Leroy (CS GROUP)
2026-04-27 17:13 ` [RFC PATCH v1 2/9] uaccess: Convert INLINE_COPY_{TO/FROM}_USER to kconfig and reduce ifdefery Christophe Leroy (CS GROUP)
2026-04-27 18:39 ` Yury Norov
2026-04-27 17:13 ` [RFC PATCH v1 3/9] x86/umip: Be stricter in fixup_umip_exception() Christophe Leroy (CS GROUP)
2026-04-27 17:13 ` [RFC PATCH v1 4/9] uaccess: Introduce copy_{to/from}_user_partial() Christophe Leroy (CS GROUP)
2026-04-27 17:13 ` [RFC PATCH v1 5/9] uaccess: Switch to copy_{to/from}_user_partial() when relevant Christophe Leroy (CS GROUP)
2026-04-27 18:07 ` Alice Ryhl
2026-04-27 19:01 ` Linus Torvalds
2026-04-27 21:29 ` David Laight
2026-04-27 21:39 ` Linus Torvalds
2026-04-27 17:13 ` [RFC PATCH v1 6/9] uaccess: Change copy_{to/from}_user to return -EFAULT Christophe Leroy (CS GROUP)
2026-04-27 17:13 ` [RFC PATCH v1 7/9] x86: Add unsafe_copy_from_user() Christophe Leroy (CS GROUP)
2026-04-27 17:58 ` Yury Norov
2026-04-27 18:20 ` Christophe Leroy (CS GROUP)
2026-04-27 19:19 ` Yury Norov
2026-04-27 17:13 ` [RFC PATCH v1 8/9] arm64: " Christophe Leroy (CS GROUP)
2026-04-27 17:13 ` [RFC PATCH v1 9/9] uaccess: Convert small fixed size copy_{to/from}_user() to scoped user access Christophe Leroy (CS GROUP)
2026-04-27 20:12 ` Yury Norov [this message]
2026-04-27 19:01 ` [RFC PATCH v1 0/9] " Helge Deller
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