From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 6618 invoked by alias); 30 Nov 2016 10:08:57 -0000 Mailing-List: contact gdb-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: gdb-owner@sourceware.org Received: (qmail 6477 invoked by uid 89); 30 Nov 2016 10:08:56 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=-3.8 required=5.0 tests=BAYES_00,KAM_LAZY_DOMAIN_SECURITY,RP_MATCHES_RCVD,SPF_HELO_PASS autolearn=ham version=3.3.2 spammy=H*r:sk:dhcp-19, controversial, guests, KVM X-Spam-User: qpsmtpd, 2 recipients X-HELO: mx1.redhat.com Received: from mx1.redhat.com (HELO mx1.redhat.com) (209.132.183.28) by sourceware.org (qpsmtpd/0.93/v0.84-503-g423c35a) with ESMTP; Wed, 30 Nov 2016 10:08:54 +0000 Received: from int-mx09.intmail.prod.int.phx2.redhat.com (int-mx09.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 4510FC054902; Wed, 30 Nov 2016 10:08:53 +0000 (UTC) Received: from oldenburg.str.redhat.com (dhcp-192-212.str.redhat.com [10.33.192.212]) by int-mx09.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with ESMTP id uAUA8ouO019953 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO); Wed, 30 Nov 2016 05:08:51 -0500 Subject: Re: [RFC PATCH 00/29] arm64: Scalable Vector Extension core support To: Dave Martin , linux-arm-kernel@lists.infradead.org References: <1480102762-23647-1-git-send-email-Dave.Martin@arm.com> Cc: Christoffer Dall , Ard Biesheuvel , Marc Zyngier , Alan Hayward , libc-alpha@sourceware.org, gdb@sourceware.org, Torvald Riegel From: Florian Weimer Message-ID: <7a35d1ae-73df-03a5-c9d6-1a52754acf25@redhat.com> Date: Wed, 30 Nov 2016 10:08:00 -0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.4.0 MIME-Version: 1.0 In-Reply-To: <1480102762-23647-1-git-send-email-Dave.Martin@arm.com> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit X-IsSubscribed: yes X-SW-Source: 2016-11/txt/msg00064.txt.bz2 On 11/25/2016 08:38 PM, Dave Martin wrote: > The Scalable Vector Extension (SVE) [1] is an extension to AArch64 which > adds extra SIMD functionality and supports much larger vectors. > > This series implements core Linux support for SVE. > > Recipents not copied on the whole series can find the rest of the > patches in the linux-arm-kernel archives [2]. > > > The first 5 patches "arm64: signal: ..." factor out the allocation and > placement of state information in the signal frame. The first three > are prerequisites for the SVE support patches. > > Patches 04-05 implement expansion of the signal frame, and may remain > controversial due to ABI break issues: > > * Discussion is needed on how userspace should detect/negotiate signal > frame size in order for this expansion mechanism to be workable. I'm leaning towards a simple increase in the glibc headers (despite the ABI risk), plus a personality flag to disable really wide vector registers in case this causes problems with old binaries. A more elaborate mechanism will likely introduce more bugs than it makes existing applications working, due to its complexity. > The remaining patches implement initial SVE support for Linux, with the > following limitations: > > * No KVM/virtualisation support for guests. > > * No independent SVE vector length configuration per thread. This is > planned, but will follow as a separate add-on series. Per-thread register widths will likely make coroutine switching (setcontext) and C++ resumable functions/executors quite challenging. Can you detail your plans in this area? Thanks, Florian