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 08C0CC636CC for ; Thu, 16 Feb 2023 10:57:30 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1pSbwK-0004lU-4K; Thu, 16 Feb 2023 05:56:36 -0500 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 1pSbwI-0004fl-KZ for qemu-devel@nongnu.org; Thu, 16 Feb 2023 05:56:34 -0500 Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1pSbwH-0002bR-0q for qemu-devel@nongnu.org; Thu, 16 Feb 2023 05:56:34 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1676544992; h=from:from:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=T3U9QORg0lMd3ZC9KFcgulk0hNSFicEtxMcrNkm32BI=; b=MPQDxKA8zIut/lzsEfhuJKgg8tt9ARSq+bwe8llLr4VAVAnaClwXh2Jy+7NhjSMtrRiL4f L2l23Nvyyj/ZlHRGI8ytAQcbZo2JV++Q67JzF184lDXy5ZeiOVohfJXSlX7Xh2Iz1dAAop 65TWg9wdbjFihMge9bRm9aWl4mrUPFg= Received: from mail-wm1-f69.google.com (mail-wm1-f69.google.com [209.85.128.69]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_128_GCM_SHA256) id us-mta-121-2x2UChKiM3uoZHJSpctECQ-1; Thu, 16 Feb 2023 05:56:30 -0500 X-MC-Unique: 2x2UChKiM3uoZHJSpctECQ-1 Received: by mail-wm1-f69.google.com with SMTP id p14-20020a05600c468e00b003e0107732f4so680051wmo.1 for ; Thu, 16 Feb 2023 02:56:30 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=content-transfer-encoding:mime-version:message-id:date:reply-to :user-agent:references:in-reply-to:subject:cc:to:from :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=T3U9QORg0lMd3ZC9KFcgulk0hNSFicEtxMcrNkm32BI=; b=aaUbW36bMroyZ0WTwM/UzvAAIYVEcO5nnS+ojJT1GM/FOvySJUAP0vrc0ucAM0Ht4G S00ftY6+55ynzSwCU5uH8cd7vzCgVf824Fh4AiiJGwj0FKKQrslI3K0S1hk8NlIQyrKk qv6ZSLGvmriZ6BmCdhQuDKqTK4YanSbWcRpu9wWRNa8vVhd1yBCZ1saRU2iwLVpFE1it Bq6VyLm5Ws6Qm8rU20k7cvR285YkJ8uJPUrb3ZdMuI9Du53FleLUjw+SDq9s7Frk7Zgo g/VzW5gRdGaNoDvtQRM0XFpH0+49v8pAma0Etz2Ks1pJXbva0aGBS9RNxqyCbnjcM5ef eU1Q== X-Gm-Message-State: AO0yUKXHb9Qz7cuq6I+j4GgH/3FyFdIZadjMYB4Qk1U2Ny0V54tgAKSk +za1pDhAxHb5RJ/dIOtfnsAlXYDvryTAd8TBq4GevFaHkb6o7GI2Qr7XS9MAHyVBW5cjQlQOyRM Mn+IIRG1aP+A4P8w= X-Received: by 2002:adf:e451:0:b0:2c5:4c0e:3736 with SMTP id t17-20020adfe451000000b002c54c0e3736mr4576266wrm.24.1676544989690; Thu, 16 Feb 2023 02:56:29 -0800 (PST) X-Google-Smtp-Source: AK7set/s1kQ5/nTGSeeqbDHy+KXBxzku9V02rWwVSa3oPfOlRK7tu8CFgXaDNMxPoRZGeqhs2jA40A== X-Received: by 2002:adf:e451:0:b0:2c5:4c0e:3736 with SMTP id t17-20020adfe451000000b002c54c0e3736mr4576254wrm.24.1676544989358; Thu, 16 Feb 2023 02:56:29 -0800 (PST) Received: from redhat.com ([46.136.252.173]) by smtp.gmail.com with ESMTPSA id h17-20020a056000001100b002c54c8e70b1sm1203774wrx.9.2023.02.16.02.56.28 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 16 Feb 2023 02:56:28 -0800 (PST) From: Juan Quintela To: Alex =?utf-8?Q?Benn=C3=A9e?= Cc: Paolo Bonzini , Pavel Dovgalyuk , "qemu-devel@nongnu.org" , Richard Henderson , Mark Burton , Bill Mills , Marco Liebel , Alexandre Iooss , Mahmoud Mandour , Emilio Cota , Philippe =?utf-8?Q?Mathieu-Daud=C3=A9?= , "Wei W. Wang" Subject: Re: Future of icount discussion for next KVM call? In-Reply-To: ("Alex =?utf-8?Q?Benn=C3=A9e=22's?= message of "Thu, 16 Feb 2023 10:23:58 +0000") References: <87bklt9alc.fsf@linaro.org> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/28.2 (gnu/linux) Date: Thu, 16 Feb 2023 11:56:27 +0100 Message-ID: <87lekxkhes.fsf@secure.mitica> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Received-SPF: pass client-ip=170.10.129.124; envelope-from=quintela@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H2=-0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 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: , Reply-To: quintela@redhat.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Alex Benn=C3=A9e wrote: > (replying all because qemu-devel rejected my email again) > > On Thu, 16 Feb 2023 at 10:19, Alex Benn=C3=A9e w= rote: > >> Hi Juan, >> >> Do we have an agenda for next weeks KVM call yet? If there is space I'd >> like to take some time to discuss the future direction of icount. For next week we have: - more single binary qemu (philippe?) - TDX migration from intel. We asked them on the previous call to change their design to transfer stuff through migration channels and not create a new channel. But I haven't heard from intel. (wei?) They agreed to send the slides and post the code before continue discussion. And now I like the title of you topic - Future Direction of icount O:-) So, I will recommend 20 minutes each if Wei shows up, or 30/30 for the rest. What do the rest of the people think. >> Specifically I believe there might be some proposals for how we could >> support icount with MTTCG worth discussing. From my point of view icount >> provides too things: >> >> - a sense of time vaguely related to execution rather than wall clock >> - determinism >> >> I would love to divorce the former from icount and punt it to plugins. >> The plugin would be free to instrument as heavily or lightly as it sees >> fit and provide its best guess as to guest time on demand. I wrote this >> idea up as a card in Linaro's JIRA if anyone is interested: >> >> https://linaro.atlassian.net/browse/QEMU-481 >> >> Being able to punt cost modelling and sense of time into plugins would >> allow the core icount support to concentrate on determinism. Then any >> attempt to enable icount for MTTCG would then have to ensure it stays >> deterministic. >> >> Richard and I have discussed the problem a few times and weren't sure it >> was solvable but I'm totally open to hearing ideas on how to do it. >> Fundamentally I think we would have to ensure any TB's doing IO would >> have to execute in an exclusive context. The TCG code already has >> mechanisms to ensure all IO is only done at the end of blocks so it >> doesn't seem a huge leap to ensure we execute those blocks exclusively. >> However there is still the problem of what to do about other pure >> computation threads getting ahead or behind of the IO blocks on >> subsequent runs. >> >> Anyway does anyone else have ideas to bring to the discussion? Hat on to you O:-) Open discussion with a Jira Epic and a good introduction. I am sorry that I am not an expert (or even newbie) on that part of qemu to give apport anything. Thanks, Juan.