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.xenproject.org (lists.xenproject.org [192.237.175.120]) (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 20B6BC47077 for ; Thu, 11 Jan 2024 14:16:14 +0000 (UTC) Received: from list by lists.xenproject.org with outflank-mailman.666302.1036832 (Exim 4.92) (envelope-from ) id 1rNvqj-000800-FV; Thu, 11 Jan 2024 14:16:01 +0000 X-Outflank-Mailman: Message body and most headers restored to incoming version Received: by outflank-mailman (output) from mailman id 666302.1036832; Thu, 11 Jan 2024 14:16:01 +0000 Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1rNvqj-0007zt-Cr; Thu, 11 Jan 2024 14:16:01 +0000 Received: by outflank-mailman (input) for mailman id 666302; Thu, 11 Jan 2024 14:16:00 +0000 Received: from se1-gles-sth1-in.inumbo.com ([159.253.27.254] helo=se1-gles-sth1.inumbo.com) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1rNvqi-0007zl-5Y for xen-devel@lists.xenproject.org; Thu, 11 Jan 2024 14:16:00 +0000 Received: from mail-wm1-x32a.google.com (mail-wm1-x32a.google.com [2a00:1450:4864:20::32a]) by se1-gles-sth1.inumbo.com (Halon) with ESMTPS id f14bcedb-b08b-11ee-98f0-6d05b1d4d9a1; Thu, 11 Jan 2024 15:15:59 +0100 (CET) Received: by mail-wm1-x32a.google.com with SMTP id 5b1f17b1804b1-40e624a8cbbso2607905e9.2 for ; Thu, 11 Jan 2024 06:15:59 -0800 (PST) Received: from localhost ([213.195.127.70]) by smtp.gmail.com with ESMTPSA id iv17-20020a05600c549100b0040e5034d8e0sm6003466wmb.43.2024.01.11.06.15.58 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 11 Jan 2024 06:15:58 -0800 (PST) X-BeenThere: xen-devel@lists.xenproject.org List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Errors-To: xen-devel-bounces@lists.xenproject.org Precedence: list Sender: "Xen-devel" X-Inumbo-ID: f14bcedb-b08b-11ee-98f0-6d05b1d4d9a1 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=citrix.com; s=google; t=1704982558; x=1705587358; darn=lists.xenproject.org; h=in-reply-to:content-transfer-encoding:content-disposition :mime-version:references:message-id:subject:cc:to:from:date:from:to :cc:subject:date:message-id:reply-to; bh=jGR/JQnhf1qU/ywHOv+2ixBYeb5XleYTse6KIYOcI9U=; b=F0MwCW1gFGOn1GpPZw+FnFRuVN8rt3G1YU1DDSfn11kwE/Kps2K6acBOaCfhmBRGeZ GL2dq1Epb0e1hh66KaFr/mumNVIkhpky6jnWsJmmP4CfK+8hm+K7+a4duXcpv/4xjRzN KdwubZeQo3JyBcJSRWbXRGJIaX49HFYuIB9TQ= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1704982558; x=1705587358; h=in-reply-to:content-transfer-encoding:content-disposition :mime-version:references:message-id:subject:cc:to:from:date :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=jGR/JQnhf1qU/ywHOv+2ixBYeb5XleYTse6KIYOcI9U=; b=oq1O/XrBdofvf+8XiRJv5g07zLX1+9sGZcIqaXv+k6yiTVhnPhvNGzWWgtQ+CVliWg Lrv8ZNCq3erUpRSvbJub3hf3ni5r3W7Ii8ilDDM1bdBIlA+4+ovFi8KPUQFFDH/FK3Po CiorrLFbgSY3hXEXQuXm8r+6kwgDFKyxroYaxkNjRMddM3B+CQSWlpb5kP9W7jYGisMa KV/762wAFhpM/t5HQsnow6ixQuPLKNAQxzWXdncCFEJn6wyeP/9NP0tar4tAgrAm4arQ yxqGmGU21P5BMLPjTkDQ5/pgRgZhW+w114sJwzQ7okMgfjGVyns5L5KFsBxxE5+CGqoG kUHA== X-Gm-Message-State: AOJu0Yy/vn8Yv4rlXGBzWo8ETg76KPpH4QvmNidng5OD+y4MWPmbf8hf X819IEH2zCHFm9QVuigDsRO+8UaWuo6tdr9ggfV3PeR1lb0= X-Google-Smtp-Source: AGHT+IGIw6mcGyiFePA8NkUBvE6J0kAC+LykI3Eg1JGOvX1NkVa/jeum5/O67eGDOa8C5aQbMc+0tg== X-Received: by 2002:a05:600c:5026:b0:40e:6240:3293 with SMTP id n38-20020a05600c502600b0040e62403293mr235387wmr.40.1704982558628; Thu, 11 Jan 2024 06:15:58 -0800 (PST) Date: Thu, 11 Jan 2024 15:15:57 +0100 From: Roger Pau =?utf-8?B?TW9ubsOp?= To: Jan Beulich Cc: Andrew Cooper , Wei Liu , xen-devel@lists.xenproject.org Subject: Re: [PATCH v2] x86/intel: ensure Global Performance Counter Control is setup correctly Message-ID: References: <20240111090821.67594-1-roger.pau@citrix.com> <3428928a-42d0-4e4b-9607-c184968c309d@suse.com> <645e0c95-5a12-4202-8da6-3cc789a9e5c7@suse.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: On Thu, Jan 11, 2024 at 03:01:01PM +0100, Jan Beulich wrote: > On 11.01.2024 13:22, Roger Pau Monné wrote: > > Oh, indeed, can adjust on this same patch if that's OK (seeing as the > > issue was already there previous to my change). > > Well, I'm getting the impression that it was deliberate there, i.e. set > setting of the feature flag may want to remain thus constrained. Hm, I find it weird, but the original commit message doesn't help at all. Xen itself only uses PMC0, and I don't find any other justification in the current code to require at least 2 counters in order to expose arch performance monitoring to be present. Looking at the SDM vol3, the figures there only contain PMC0 and PMC1, so someone only reading that manual might assume there must always be 2 global PMCs? (vol4 clarifies the that the number of global PMCs is variable). Thanks, Roger.