From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dave Martin Subject: Re: [RFC PATCH 07/10] arm64/sve: Add vector length inheritance control Date: Mon, 16 Jan 2017 13:34:44 +0000 Message-ID: <20170116133443.GP3699@e103592.cambridge.arm.com> References: <1484220369-23970-1-git-send-email-Dave.Martin@arm.com> <1484220369-23970-8-git-send-email-Dave.Martin@arm.com> <20170116122755.GH28060@E107787-LIN> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from foss.arm.com ([217.140.101.70]:53578 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751358AbdAPNet (ORCPT ); Mon, 16 Jan 2017 08:34:49 -0500 Content-Disposition: inline In-Reply-To: <20170116122755.GH28060@E107787-LIN> Sender: linux-arch-owner@vger.kernel.org List-ID: To: Yao Qi Cc: linux-arch@vger.kernel.org, Florian Weimer , libc-alpha@sourceware.org, Ard Biesheuvel , Marc Zyngier , gdb@sourceware.org, Joseph Myers , Szabolcs Nagy , linux-arm-kernel@lists.infradead.org, Alan Hayward , Torvald Riegel , Christoffer Dall On Mon, Jan 16, 2017 at 12:27:55PM +0000, Yao Qi wrote: > On 17-01-12 11:26:06, Dave Martin wrote: > > Currently the vector length is inherited across both fork() and > > exec(). > > > > Inheritance across fork() is desirable both for creating a copy of > > a process (traditional fork) or creating a thread (where we want > > all threads to share the same VL by default). > > > > Inheritance across exec() is less desirable, because of the ABI > > impact of large vector lengths on the size of the signal frame -- > > when running a new binary, there is no guarantee that the new > > binary is compatible with these ABI changes. > > > > This flag makes the vector length non-inherited by default. > > Can we make vector length inherited across fork but non-inherited > across exec by default? That is the behaviour: I always inherit across fork/clone, since you are still running the same binary after those. I could word the commit message a bit more clearly here. Cheers ---Dave