From: qiyaoltc@gmail.com (Yao Qi)
To: linux-arm-kernel@lists.infradead.org
Subject: [RFC PATCH 06/10] arm64/sve: Disallow VL setting for individual threads by default
Date: Mon, 16 Jan 2017 11:34:39 +0000 [thread overview]
Message-ID: <20170116113439.GF28060@E107787-LIN> (raw)
In-Reply-To: <1484220369-23970-7-git-send-email-Dave.Martin@arm.com>
On 17-01-12 11:26:05, Dave Martin wrote:
> General-purpose code in userspace is not expected to work correctly
> if multiple threads are allowed to run concurrently with different
> vector lengths in a single process.
>
> This patch adds an explicit flag PR_SVE_SET_VL_THREAD to request
> this behaviour. Without the flag, vector length setting is
> permitted only for a single-threaded process (which matches the
> expected usage model of setting the vector length at process
> startup).
Hi Dave,
PR_SVE_SET_VL_THREAD can be arch-independent, IMO, because prctl
needs a scope. Looks some of them are system-wide, some of them are
about threads within the same process (like, PR_MPX_ENABLE_MANAGEMENT).
IOW, PR_SVE_SET_VL_THREAD can be general flag, to indicate the scope
of each new ptrcl command is per-thread.
I happen to see PR_SET_FP_MODE in man pages, which is about setting
FP register modes in runtime. It is a little similar to setting VL in
this patch. However the doc doesn't mention the effect or the scope
of this command.
--
Yao (??)
next prev parent reply other threads:[~2017-01-16 11:34 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-01-12 11:25 [RFC PATCH 00/10] arm64/sve: Add userspace vector length control API Dave Martin
2017-01-12 11:26 ` [RFC PATCH 01/10] prctl: Add skeleton for PR_SVE_{SET, GET}_VL controls Dave Martin
2017-01-12 11:26 ` [RFC PATCH 02/10] arm64/sve: Track vector length for each task Dave Martin
2017-01-12 11:26 ` [RFC PATCH 03/10] arm64/sve: Set CPU vector length to match current task Dave Martin
2017-01-12 11:26 ` [RFC PATCH 04/10] arm64/sve: Factor out clearing of tasks' SVE regs Dave Martin
2017-01-12 11:26 ` [RFC PATCH 05/10] arm64/sve: Wire up vector length control prctl() calls Dave Martin
2017-01-12 11:26 ` [RFC PATCH 06/10] arm64/sve: Disallow VL setting for individual threads by default Dave Martin
2017-01-16 11:34 ` Yao Qi [this message]
2017-01-16 12:23 ` Dave Martin
2017-01-12 11:26 ` [RFC PATCH 07/10] arm64/sve: Add vector length inheritance control Dave Martin
2017-01-16 12:27 ` Yao Qi
2017-01-16 13:34 ` Dave Martin
2017-01-12 11:26 ` [RFC PATCH 08/10] arm64/sve: ptrace: Wire up vector length control and reporting Dave Martin
2017-01-16 12:20 ` Yao Qi
2017-01-16 13:32 ` Dave Martin
2017-01-16 15:11 ` Yao Qi
2017-01-16 15:47 ` Pedro Alves
2017-01-16 16:31 ` Dave Martin
2017-01-17 10:03 ` Dave Martin
2017-01-17 13:31 ` Alan Hayward
2017-01-19 17:11 ` Dave Martin
2017-01-12 11:26 ` [RFC PATCH 09/10] arm64/sve: Enable default vector length control via procfs Dave Martin
2017-01-12 11:26 ` [RFC PATCH 10/10] Revert "arm64/sve: Limit vector length to 512 bits by default" Dave Martin
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