From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from lindbergh.monkeyblade.net (lindbergh.monkeyblade.net [23.128.96.19]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 22CEB18E11 for ; Mon, 2 Oct 2023 13:30:14 +0000 (UTC) Received: from mail-ej1-x62e.google.com (mail-ej1-x62e.google.com [IPv6:2a00:1450:4864:20::62e]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3F402AD; Mon, 2 Oct 2023 06:30:12 -0700 (PDT) Received: by mail-ej1-x62e.google.com with SMTP id a640c23a62f3a-9a58dbd5daeso2323745166b.2; Mon, 02 Oct 2023 06:30:12 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1696253411; x=1696858211; darn=vger.kernel.org; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:sender:from:to:cc:subject:date:message-id :reply-to; bh=q8lMj7UsL/Ml50KMNpFYKOAmY39cvImv/aSmmjUAHj8=; b=fsHBrjmmr8V+2Cn4jh0hnaIZ6RVqbSbn8ld1nKB4fd72KDBztOllkZRiMBorriMJOr 0NeHEYmoRGq6odKLps3XcqxMH65/uhSphgqO3eBxF212gLpph634ZH47Oczxobd0dmID q1NT9uhFZxUiPWH3NPbF+j8iTKud2SkjP+WXsiHVgr0FSdF13vH24RonWasZDA7UeyAg LQD29+r/wSP89ynnirB9nEoVQ8sYe0GzgOzDC5RZcOLdjo3CSVTzMkUdrGtxhQZn08ms X0qkoHf23BFP+CEwMKrkY8S0gF74aERjOuWURkBPvfdHRsOOrzxEkciNShdwoBVWXEbX 5Rmg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1696253411; x=1696858211; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:sender:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=q8lMj7UsL/Ml50KMNpFYKOAmY39cvImv/aSmmjUAHj8=; b=YZXKZRmDZ1jzHtmS8z3THHTnpsWXfJIlSFGeg7wbQ2ngvTqiuzqECcPZDwxlUcGY3G zIT6nl86DzW2Z/zQ7Ig6yn0KNJ8u9dg6isFNK859RGAWsaSpMk0UvCZS+ZPvCal8vyW4 IR7ElM6J88IOTxmMVYDrYP0pcRH9OL14WICwXWf8IJGY8rcDSAOXQArtetQV+VsOu+Fy 3A8vH1lhZxR7ISBbsC5c2LtxaVcr2h1cwzJsHgdHbkzKZk0UMoMU9WyDajyf/YjIub89 vNO7g6OcuDFuIAcjtsckzk0NpMGa+gyOFrn2TGtTzBPG6V3lvrv+8xmo3MV3iXK29kPX BzRg== X-Gm-Message-State: AOJu0YwpGbDA99WGdzCNwEy3hzvtGKE6caPeuJUJUXa+Gsh3BWkGZJNH VA+ca6sEorNRuI2ZQO24FY8= X-Google-Smtp-Source: AGHT+IE1iH0CKusjU61Wbpb/lh63BPpwJy5u9+b6RQsHxM8FLrHqhuy0m8IBSPfzycAvYWrGEi997A== X-Received: by 2002:a17:906:58c6:b0:9b2:6ce3:bdf3 with SMTP id e6-20020a17090658c600b009b26ce3bdf3mr13024153ejs.54.1696253410572; Mon, 02 Oct 2023 06:30:10 -0700 (PDT) Received: from gmail.com (1F2EF530.nat.pool.telekom.hu. [31.46.245.48]) by smtp.gmail.com with ESMTPSA id ox12-20020a170907100c00b00988f168811bsm17030237ejb.135.2023.10.02.06.30.08 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 02 Oct 2023 06:30:09 -0700 (PDT) Sender: Ingo Molnar Date: Mon, 2 Oct 2023 15:30:07 +0200 From: Ingo Molnar To: Peter Zijlstra Cc: Sean Christopherson , Dapeng Mi , Paolo Bonzini , Arnaldo Carvalho de Melo , Kan Liang , Like Xu , Mark Rutland , Alexander Shishkin , Jiri Olsa , Namhyung Kim , Ian Rogers , Adrian Hunter , kvm@vger.kernel.org, linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org, Zhenyu Wang , Zhang Xiong , Lv Zhiyuan , Yang Weijiang , Dapeng Mi , Jim Mattson , David Dunn , Mingwei Zhang , Thomas Gleixner Subject: Re: [Patch v4 07/13] perf/x86: Add constraint for guest perf metrics event Message-ID: References: <20230927033124.1226509-1-dapeng1.mi@linux.intel.com> <20230927033124.1226509-8-dapeng1.mi@linux.intel.com> <20230927113312.GD21810@noisy.programming.kicks-ass.net> <20230929115344.GE6282@noisy.programming.kicks-ass.net> <20231002115718.GB13957@noisy.programming.kicks-ass.net> Precedence: bulk X-Mailing-List: linux-perf-users@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20231002115718.GB13957@noisy.programming.kicks-ass.net> X-Spam-Status: No, score=-1.5 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_EF,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,RCVD_IN_DNSWL_BLOCKED,SPF_HELO_NONE, SPF_PASS autolearn=no autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net * Peter Zijlstra wrote: > On Fri, Sep 29, 2023 at 03:46:55PM +0000, Sean Christopherson wrote: > > > > I will firmly reject anything that takes the PMU away from the host > > > entirely through. > > > > Why? What is so wrong with supporting use cases where the platform owner *wants* > > to give up host PMU and NMI watchdog functionality? If disabling host PMU usage > > were complex, highly invasive, and/or difficult to maintain, then I can understand > > the pushback. > > Because it sucks. > > You're forcing people to choose between no host PMU or a slow guest PMU. > And that's simply not a sane choice for most people -- worse it's not a > choice based in technical reality. > > It's a choice out of lazyness, disabling host PMU is not a requirement > for pass-through. Not just a choice of laziness, but it will clearly be forced upon users by external entities: "Pass ownership of the PMU to the guest and have no host PMU, or you won't have sane guest PMU support at all. If you disagree, please open a support ticket, which we'll ignore." The host OS shouldn't offer facilities that severely limit its own capabilities, when there's a better solution. We don't give the FPU to apps exclusively either, it would be insanely stupid for a platform to do that. Thanks, Ingo