From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-3.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id CA8EEC83018 for ; Wed, 2 Dec 2020 17:21:38 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 817FB221E9 for ; Wed, 2 Dec 2020 17:21:37 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 817FB221E9 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=bugs.launchpad.net Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:37348 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1kkVot-0004RY-6d for qemu-devel@archiver.kernel.org; Wed, 02 Dec 2020 12:21:35 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:58844) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1kkVo5-0003sB-2l for qemu-devel@nongnu.org; Wed, 02 Dec 2020 12:20:45 -0500 Received: from indium.canonical.com ([91.189.90.7]:58098) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.90_1) (envelope-from ) id 1kkVo1-0007SK-O4 for qemu-devel@nongnu.org; Wed, 02 Dec 2020 12:20:44 -0500 Received: from loganberry.canonical.com ([91.189.90.37]) by indium.canonical.com with esmtp (Exim 4.86_2 #2 (Debian)) id 1kkVnz-0003zw-QW for ; Wed, 02 Dec 2020 17:20:39 +0000 Received: from loganberry.canonical.com (localhost [127.0.0.1]) by loganberry.canonical.com (Postfix) with ESMTP id C34752E813A for ; Wed, 2 Dec 2020 17:20:39 +0000 (UTC) MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Date: Wed, 02 Dec 2020 17:05:42 -0000 From: =?utf-8?q?Philippe_Mathieu-Daud=C3=A9?= <1906536@bugs.launchpad.net> To: qemu-devel@nongnu.org X-Launchpad-Notification-Type: bug X-Launchpad-Bug: product=qemu; status=Invalid; importance=Undecided; assignee=None; X-Launchpad-Bug-Tags: arm linux-user X-Launchpad-Bug-Information-Type: Public X-Launchpad-Bug-Private: no X-Launchpad-Bug-Security-Vulnerability: no X-Launchpad-Bug-Commenters: alecop philmd X-Launchpad-Bug-Reporter: Alex Coplan (alecop) X-Launchpad-Bug-Modifier: =?utf-8?q?Philippe_Mathieu-Daud=C3=A9_=28philmd?= =?utf-8?q?=29?= References: <160692480491.27592.13493676422712150173.malonedeb@chaenomeles.canonical.com> Message-Id: <160692874216.26254.12267648197584238813.malone@chaenomeles.canonical.com> Subject: [Bug 1906536] Re: Unable to set SVE VL to 1024 bits or above since 7b6a2198 X-Launchpad-Message-Rationale: Subscriber (QEMU) @qemu-devel-ml X-Launchpad-Message-For: qemu-devel-ml Precedence: bulk X-Generated-By: Launchpad (canonical.com); Revision="55c41fea591e042b8bb54e6952942f55c764435e"; Instance="production" X-Launchpad-Hash: b719e53592dce5719708128ec2aa8382c2a46146 Received-SPF: none client-ip=91.189.90.7; envelope-from=bounces@canonical.com; helo=indium.canonical.com X-Spam_score_int: -65 X-Spam_score: -6.6 X-Spam_bar: ------ X-Spam_report: (-6.6 / 5.0 requ) BAYES_00=-1.9, HEADER_FROM_DIFFERENT_DOMAINS=0.25, RCVD_IN_DNSWL_HI=-5, RCVD_IN_MSPIKE_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_NONE=0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: Bug 1906536 <1906536@bugs.launchpad.net> Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Hi Alex, This commit mentions: The Linux kernel chooses the default of 64 bytes for SVE registers on the basis that it is the largest size on known hardware that won't grow the signal frame. We still honour the sve-max-vq property and userspace can expand the number of lanes by calling PR_SVE_SET_VL. Expand the number of lanes by calling PR_SVE_SET_VL works for me: .global _start _start: mov x0, 50 // PR_SVE_SET_VL mov x1, 256 // 16 lanes mov x8, #167 // prctl svc #0 rdvl x0, #1 asr x0, x0, #4 mov x8, #93 // exit svc #0 $ for vl in 1 2 4 8 16; do qemu-aarch64 -strace -cpu max,sve-max-vq=3D$vl a= .out; echo $?; done 1383321 prctl(50,256,0,0,0,0) =3D 16 1383321 exit(1) 1 1383323 prctl(50,256,0,0,0,0) =3D 32 1383323 exit(2) 2 1383325 prctl(50,256,0,0,0,0) =3D 64 1383325 exit(4) 4 1383327 prctl(50,256,0,0,0,0) =3D 128 1383327 exit(8) 8 1383329 prctl(50,256,0,0,0,0) =3D 256 1383329 exit(16) 16 ** Changed in: qemu Status: New =3D> Invalid ** Tags added: arm linux-user -- = You received this bug notification because you are a member of qemu- devel-ml, which is subscribed to QEMU. https://bugs.launchpad.net/bugs/1906536 Title: Unable to set SVE VL to 1024 bits or above since 7b6a2198 Status in QEMU: Invalid Bug description: Prior to 7b6a2198e71794c851f39ac7a92d39692c786820, the QEMU option sve-max-vq could be used to set the vector length of the implementation. This is useful (among other reasons) for testing software compiled with a fixed SVE vector length. Since this commit, the vector length is capped at 512 bits. To reproduce the issue: $ cat rdvl.s .global _start _start: rdvl x0, #1 asr x0, x0, #4 mov x8, #93 // exit svc #0 $ aarch64-linux-gnu-as -march=3Darmv8.2-a+sve rdvl.s -o rdvl.o $ aarch64-linux-gnu-ld rdvl.o $ for vl in 1 2 4 8 16; do ../build-qemu/aarch64-linux-user/qemu-aarch64 = -cpu max,sve-max-vq=3D$vl a.out; echo $?; done 1 2 4 4 4 For a QEMU built prior to the above revision, we get the output: 1 2 4 8 16 as expected. It seems that either the old behavior should be restored, or there should be an option to force a higher vector length? To manage notifications about this bug go to: https://bugs.launchpad.net/qemu/+bug/1906536/+subscriptions