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 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 smtp.lore.kernel.org (Postfix) with ESMTPS id D3854EB64D8 for ; Thu, 22 Jun 2023 07:27:13 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1qCEi4-0002xq-I8; Thu, 22 Jun 2023 03:26:30 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1qCEhw-0002xI-Gc; Thu, 22 Jun 2023 03:26:20 -0400 Received: from mail.ozlabs.org ([2404:9400:2221:ea00::3] helo=gandalf.ozlabs.org) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1qCEhu-0002vw-Hm; Thu, 22 Jun 2023 03:26:20 -0400 Received: from gandalf.ozlabs.org (gandalf.ozlabs.org [150.107.74.76]) by gandalf.ozlabs.org (Postfix) with ESMTP id 4QmsNz6bgMz4x09; Thu, 22 Jun 2023 17:26:11 +1000 (AEST) Received: from authenticated.ozlabs.org (localhost [127.0.0.1]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits)) (No client certificate requested) by mail.ozlabs.org (Postfix) with ESMTPSA id 4QmsNw4Nccz4wjD; Thu, 22 Jun 2023 17:26:08 +1000 (AEST) Message-ID: <3c31b569-6686-7643-f356-cda19cf06a14@kaod.org> Date: Thu, 22 Jun 2023 09:26:06 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.12.0 Subject: Re: [PATCH 0/4] target/ppc: TCG SMT support for spapr Content-Language: en-US To: Nicholas Piggin , qemu-ppc@nongnu.org Cc: qemu-devel@nongnu.org, Daniel Henrique Barboza , Richard Henderson , =?UTF-8?Q?Alex_Benn=c3=a9e?= , Thomas Huth , Harsh Prateek Bora , Kautuk Consul References: <20230605112323.179259-1-npiggin@gmail.com> <43ca9ac8-d383-42fd-ca29-f7cdd18d701d@kaod.org> <2756fa81-9ab8-0b15-a69e-726b47a43d41@kaod.org> From: =?UTF-8?Q?C=c3=a9dric_Le_Goater?= In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=2404:9400:2221:ea00::3; envelope-from=SRS0=yb1G=CK=kaod.org=clg@ozlabs.org; helo=gandalf.ozlabs.org X-Spam_score_int: -40 X-Spam_score: -4.1 X-Spam_bar: ---- X-Spam_report: (-4.1 / 5.0 requ) BAYES_00=-1.9, HEADER_FROM_DIFFERENT_DOMAINS=0.249, NICE_REPLY_A=-0.093, RCVD_IN_DNSWL_MED=-2.3, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On 6/20/23 12:45, Nicholas Piggin wrote: > On Tue Jun 20, 2023 at 8:27 PM AEST, Cédric Le Goater wrote: >> On 6/20/23 12:12, Nicholas Piggin wrote: >>> On Wed Jun 7, 2023 at 12:09 AM AEST, Cédric Le Goater wrote: >>>> On 6/5/23 13:23, Nicholas Piggin wrote: >>>>> Previous RFC here >>>>> >>>>> https://lists.gnu.org/archive/html/qemu-ppc/2023-05/msg00453.html >>>>> >>>>> This series drops patch 1 from the previous, which is more of >>>>> a standalone bugfix. >>>>> >>>>> Also accounted for Cedric's comments, except a nicer way to >>>>> set cpu_index vs PIR/TIR SPRs, which is not quite trivial. >>>>> >>>>> This limits support for SMT to POWER8 and newer. It is also >>>>> incompatible with nested-HV so that is checked for too. >>>>> >>>>> Iterating CPUs to find siblings for now I kept because similar >>>>> loops exist in a few places, and it is not conceptually >>>>> difficult for SMT, just fiddly code to improve. For now it >>>>> should not be much performane concern. >>>>> >>>>> I removed hypervisor msgsnd support from patch 3, which is not >>>>> required for spapr and added significantly to the patch. >>>>> >>>>> For now nobody has objected to the way shared SPR access is >>>>> handled (serialised with TCG atomics support) so we'll keep >>>>> going with it. >>>> >>>> Cc:ing more people for possible feedback. >>> >>> Not much feedback so I'll plan to go with this. >>> >>> A more performant implementation might try to synchronize >>> threads at the register level rather than serialize everything, >>> but SMT shared registers are not too performance critical so >>> this should do for now. >> >> yes. Could you please rebase this series on upstream ? > > Oh yeah I should have said, I will rebase and resend. Here is a tree to check the rebase on : https://github.com/legoater/qemu/commits/ppc-next >> It would be good to add tests for SMT. May be we could extend : >> >> tests/avocado/ppc_pseries.py >> >> with a couple of extra QEMU configs adding 'threads=' (if possible) and >> check : >> >> "CPU maps initialized for Y threads per core" >> >> and >> >> "smp: Brought up 1 node, X*Y CPUs" >> >> ? > > Yeah that could be a good idea, I'll try it. It can come later. Thanks, C.