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From: Jonathan Corbet <corbet@lwn.net>
To: Thomas =?utf-8?Q?Wei=C3=9Fschuh?= <linux@weissschuh.net>, Thomas
 Gleixner
 <tglx@linutronix.de>, Borislav Petkov <bp@alien8.de>, Peter Zijlstra
 <peterz@infradead.org>, Josh Poimboeuf <jpoimboe@kernel.org>, Pawan Gupta
 <pawan.kumar.gupta@linux.intel.com>, "Joel Fernandes (Google)"
 <joel@joelfernandes.org>, Chris Hyser <chris.hyser@oracle.com>, Josh Don
 <joshdon@google.com>
Cc: linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org,
 stable@vger.kernel.org, Thomas =?utf-8?Q?Wei=C3=9Fschuh?=
 <linux@weissschuh.net>
Subject: Re: [PATCH] admin-guide/hw-vuln/core-scheduling: fix return type of
 PR_SCHED_CORE_GET
In-Reply-To: <20240423-core-scheduling-cookie-v1-1-5753a35f8dfc@weissschuh.net>
References: <20240423-core-scheduling-cookie-v1-1-5753a35f8dfc@weissschuh.net>
Date: Wed, 24 Apr 2024 13:04:41 -0600
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Thomas Wei=C3=9Fschuh <linux@weissschuh.net> writes:

> sched_core_share_pid() copies the cookie to userspace with
> put_user(id, (u64 __user *)uaddr), expecting 64 bits of space.
> The "unsigned long" datatype that is documented in core-scheduling.rst
> however is only 32 bits large on 32 bit architectures.
>
> Document "unsigned long long" as the correct data type that is always
> 64bits large.
>
> This matches what the selftest cs_prctl_test.c has been doing all along.
>
> Fixes: 0159bb020ca9 ("Documentation: Add usecases, design and interface f=
or core scheduling")
> Cc: stable@vger.kernel.org
> Link: https://lore.kernel.org/util-linux/df7a25a0-7923-4f8b-a527-5e6f0064=
074d@t-8ch.de/
> Signed-off-by: Thomas Wei=C3=9Fschuh <linux@weissschuh.net>
> ---
>  Documentation/admin-guide/hw-vuln/core-scheduling.rst | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/Documentation/admin-guide/hw-vuln/core-scheduling.rst b/Docu=
mentation/admin-guide/hw-vuln/core-scheduling.rst
> index cf1eeefdfc32..a92e10ec402e 100644
> --- a/Documentation/admin-guide/hw-vuln/core-scheduling.rst
> +++ b/Documentation/admin-guide/hw-vuln/core-scheduling.rst
> @@ -67,8 +67,8 @@ arg4:
>      will be performed for all tasks in the task group of ``pid``.
>=20=20
>  arg5:
> -    userspace pointer to an unsigned long for storing the cookie returne=
d by
> -    ``PR_SCHED_CORE_GET`` command. Should be 0 for all other commands.
> +    userspace pointer to an unsigned long long for storing the cookie re=
turned
> +    by ``PR_SCHED_CORE_GET`` command. Should be 0 for all other commands.
>=20=20

Applied, thanks.

jon