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 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 51F25C433E0 for ; Mon, 4 Jan 2021 19:33:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0889721919 for ; Mon, 4 Jan 2021 19:33:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726397AbhADTdY (ORCPT ); Mon, 4 Jan 2021 14:33:24 -0500 Received: from mail.kernel.org ([198.145.29.99]:57174 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726655AbhADTdY (ORCPT ); Mon, 4 Jan 2021 14:33:24 -0500 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 3AB9720784; Mon, 4 Jan 2021 19:32:43 +0000 (UTC) Received: from disco-boy.misterjones.org ([51.254.78.96] helo=www.loen.fr) by disco-boy.misterjones.org with esmtpsa (TLS1.2) tls TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256 (Exim 4.94) (envelope-from ) id 1kwVar-005IJG-4e; Mon, 04 Jan 2021 19:32:41 +0000 MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII; format=flowed Content-Transfer-Encoding: 7bit Date: Mon, 04 Jan 2021 19:32:41 +0000 From: Marc Zyngier To: Qian Cai Cc: linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu, kernel-team@android.com, Stephen Rothwell , Linux Next Mailing List , Alexandru Elisei Subject: Re: [PATCH] KVM: arm64: Don't access PMCR_EL0 when no PMU is available In-Reply-To: <22cd2b3e8b8b278f110a3540755583efee7189fd.camel@redhat.com> References: <20201210083059.1277162-1-maz@kernel.org> <703e1b5f2db1631e8f9c55619909fe66eb069f25.camel@redhat.com> <579c839a0016107af66e704f147f9814@kernel.org> <22cd2b3e8b8b278f110a3540755583efee7189fd.camel@redhat.com> User-Agent: Roundcube Webmail/1.4.9 Message-ID: <81607700b5de4860a6f281c68ee17669@kernel.org> X-Sender: maz@kernel.org X-SA-Exim-Connect-IP: 51.254.78.96 X-SA-Exim-Rcpt-To: qcai@redhat.com, linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu, kernel-team@android.com, sfr@canb.auug.org.au, linux-next@vger.kernel.org, alexandru.elisei@arm.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: linux-next@vger.kernel.org On 2021-01-04 18:42, Qian Cai wrote: > On Mon, 2021-01-04 at 18:26 +0000, Marc Zyngier wrote: >> What I'm suggesting is this [1], which is to get rid of KVM_ARM_PMU >> completely. At least, the kernel configuration will be consistent. >> > > Do you have a patch for CONFIG_KVM to select HW_PERF_EVENTS then? I > could cook > one if not. I don't think there should be such a patch. People do disable HW_PERF_EVENTS in production in some cases, and we should honor that. All I am trying to guarantee at the moment is that the KVM configuration is consistent, as I believe that's what broke in your particular case. What needs doing is to hide the PMU registers from userspace when no PMU is configured, or even available. I'll try and post something to that effect tomorrow (hey, I'm still officially on holiday...). M. -- Jazz is not dead. It just smells funny...