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=-4.0 required=3.0 tests=BAYES_00,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 836B6C433F5 for ; Thu, 23 Sep 2021 07:45:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6C1F860EC0 for ; Thu, 23 Sep 2021 07:45:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S239706AbhIWHq7 (ORCPT ); Thu, 23 Sep 2021 03:46:59 -0400 Received: from mail.kernel.org ([198.145.29.99]:37984 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S239787AbhIWHq4 (ORCPT ); Thu, 23 Sep 2021 03:46:56 -0400 Received: from disco-boy.misterjones.org (disco-boy.misterjones.org [51.254.78.96]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 162FF60EC0; Thu, 23 Sep 2021 07:45:25 +0000 (UTC) Received: from sofa.misterjones.org ([185.219.108.64] helo=why.misterjones.org) by disco-boy.misterjones.org with esmtpsa (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.94.2) (envelope-from ) id 1mTJQ3-00CU4X-3f; Thu, 23 Sep 2021 08:45:23 +0100 Date: Thu, 23 Sep 2021 08:45:22 +0100 Message-ID: <8735pvvip9.wl-maz@kernel.org> From: Marc Zyngier To: Paolo Bonzini Cc: Sean Christopherson , Jing Zhang , KVM , KVMARM , Will Deacon , David Matlack , Peter Shier , Oliver Upton , Jim Mattson , Ben Gardon , Aaron Lewis , Venkatesh Srinivas Subject: Re: [PATCH v1 3/3] KVM: arm64: Add histogram stats for handling time of arch specific exit reasons In-Reply-To: References: <20210922010851.2312845-1-jingzhangos@google.com> <20210922010851.2312845-3-jingzhangos@google.com> <87czp0voqg.wl-maz@kernel.org> <875yusv3vm.wl-maz@kernel.org> User-Agent: Wanderlust/2.15.9 (Almost Unreal) SEMI-EPG/1.14.7 (Harue) FLIM-LB/1.14.9 (=?UTF-8?B?R29qxY0=?=) APEL-LB/10.8 EasyPG/1.0.0 Emacs/27.1 (x86_64-pc-linux-gnu) MULE/6.0 (HANACHIRUSATO) MIME-Version: 1.0 (generated by SEMI-EPG 1.14.7 - "Harue") Content-Type: text/plain; charset=US-ASCII X-SA-Exim-Connect-IP: 185.219.108.64 X-SA-Exim-Rcpt-To: pbonzini@redhat.com, seanjc@google.com, jingzhangos@google.com, kvm@vger.kernel.org, kvmarm@lists.cs.columbia.edu, will@kernel.org, dmatlack@google.com, pshier@google.com, oupton@google.com, jmattson@google.com, bgardon@google.com, aaronlewis@google.com, venkateshs@google.com X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Thu, 23 Sep 2021 07:36:21 +0100, Paolo Bonzini wrote: > > On 22/09/21 20:53, Marc Zyngier wrote: > > I definitely regret adding the current KVM trace points, as they > > don't show what I need, and I can't change them as they are ABI. > > I disagree that they are ABI. And even if you don't want to change > them, you can always add parameters or remove them. We'll have to agree to disagree here. Experience has told me that anything that gets exposed to userspace has to stay forever. There are countless examples of that on the arm64 side (cue the bogomips debate, the recent /proc/interrupts repainting). We had that discussion a few KSs ago (triggered by this[1] if I remember correctly), and I don't think anything has changed since. As for removing them, that would probably be best for some (if not most) of them. M. [1] https://lwn.net/Articles/737532/ -- Without deviation from the norm, progress is not possible. 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=-4.0 required=3.0 tests=BAYES_00,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 E9F2DC433EF for ; Thu, 23 Sep 2021 07:45:30 +0000 (UTC) Received: from mm01.cs.columbia.edu (mm01.cs.columbia.edu [128.59.11.253]) by mail.kernel.org (Postfix) with ESMTP id 677C161038 for ; Thu, 23 Sep 2021 07:45:30 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 677C161038 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=lists.cs.columbia.edu Received: from localhost (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id EC8F04B11E; Thu, 23 Sep 2021 03:45:29 -0400 (EDT) X-Virus-Scanned: at lists.cs.columbia.edu Received: from mm01.cs.columbia.edu ([127.0.0.1]) by localhost (mm01.cs.columbia.edu [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id 52B6UJz4yhLv; Thu, 23 Sep 2021 03:45:28 -0400 (EDT) Received: from mm01.cs.columbia.edu (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id ACFD04B107; Thu, 23 Sep 2021 03:45:28 -0400 (EDT) Received: from localhost (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id 7BB5C4B107 for ; Thu, 23 Sep 2021 03:45:27 -0400 (EDT) X-Virus-Scanned: at lists.cs.columbia.edu Received: from mm01.cs.columbia.edu ([127.0.0.1]) by localhost (mm01.cs.columbia.edu [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id 1bWbxyMUR9Yy for ; Thu, 23 Sep 2021 03:45:26 -0400 (EDT) Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by mm01.cs.columbia.edu (Postfix) with ESMTPS id 2F0164B0DB for ; Thu, 23 Sep 2021 03:45:26 -0400 (EDT) Received: from disco-boy.misterjones.org (disco-boy.misterjones.org [51.254.78.96]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 162FF60EC0; Thu, 23 Sep 2021 07:45:25 +0000 (UTC) Received: from sofa.misterjones.org ([185.219.108.64] helo=why.misterjones.org) by disco-boy.misterjones.org with esmtpsa (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.94.2) (envelope-from ) id 1mTJQ3-00CU4X-3f; Thu, 23 Sep 2021 08:45:23 +0100 Date: Thu, 23 Sep 2021 08:45:22 +0100 Message-ID: <8735pvvip9.wl-maz@kernel.org> From: Marc Zyngier To: Paolo Bonzini Subject: Re: [PATCH v1 3/3] KVM: arm64: Add histogram stats for handling time of arch specific exit reasons In-Reply-To: References: <20210922010851.2312845-1-jingzhangos@google.com> <20210922010851.2312845-3-jingzhangos@google.com> <87czp0voqg.wl-maz@kernel.org> <875yusv3vm.wl-maz@kernel.org> User-Agent: Wanderlust/2.15.9 (Almost Unreal) SEMI-EPG/1.14.7 (Harue) FLIM-LB/1.14.9 (=?UTF-8?B?R29qxY0=?=) APEL-LB/10.8 EasyPG/1.0.0 Emacs/27.1 (x86_64-pc-linux-gnu) MULE/6.0 (HANACHIRUSATO) MIME-Version: 1.0 (generated by SEMI-EPG 1.14.7 - "Harue") X-SA-Exim-Connect-IP: 185.219.108.64 X-SA-Exim-Rcpt-To: pbonzini@redhat.com, seanjc@google.com, jingzhangos@google.com, kvm@vger.kernel.org, kvmarm@lists.cs.columbia.edu, will@kernel.org, dmatlack@google.com, pshier@google.com, oupton@google.com, jmattson@google.com, bgardon@google.com, aaronlewis@google.com, venkateshs@google.com X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false Cc: Aaron Lewis , KVM , Venkatesh Srinivas , Peter Shier , Ben Gardon , David Matlack , Will Deacon , KVMARM , Jim Mattson X-BeenThere: kvmarm@lists.cs.columbia.edu X-Mailman-Version: 2.1.14 Precedence: list List-Id: Where KVM/ARM decisions are made List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: kvmarm-bounces@lists.cs.columbia.edu Sender: kvmarm-bounces@lists.cs.columbia.edu On Thu, 23 Sep 2021 07:36:21 +0100, Paolo Bonzini wrote: > > On 22/09/21 20:53, Marc Zyngier wrote: > > I definitely regret adding the current KVM trace points, as they > > don't show what I need, and I can't change them as they are ABI. > > I disagree that they are ABI. And even if you don't want to change > them, you can always add parameters or remove them. We'll have to agree to disagree here. Experience has told me that anything that gets exposed to userspace has to stay forever. There are countless examples of that on the arm64 side (cue the bogomips debate, the recent /proc/interrupts repainting). We had that discussion a few KSs ago (triggered by this[1] if I remember correctly), and I don't think anything has changed since. As for removing them, that would probably be best for some (if not most) of them. M. [1] https://lwn.net/Articles/737532/ -- Without deviation from the norm, progress is not possible. _______________________________________________ kvmarm mailing list kvmarm@lists.cs.columbia.edu https://lists.cs.columbia.edu/mailman/listinfo/kvmarm