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 mm01.cs.columbia.edu (mm01.cs.columbia.edu [128.59.11.253]) by smtp.lore.kernel.org (Postfix) with ESMTP id 273BEC433F5 for ; Wed, 8 Dec 2021 14:26:11 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id 7D8DA4B188; Wed, 8 Dec 2021 09:26:11 -0500 (EST) X-Virus-Scanned: at lists.cs.columbia.edu Authentication-Results: mm01.cs.columbia.edu (amavisd-new); dkim=softfail (fail, message has been altered) header.i=@kernel.org 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 JgMG8Ez77L9S; Wed, 8 Dec 2021 09:26:10 -0500 (EST) Received: from mm01.cs.columbia.edu (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id 52E2D4B165; Wed, 8 Dec 2021 09:26:10 -0500 (EST) Received: from localhost (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id 5B60A4B14D for ; Wed, 8 Dec 2021 09:26:09 -0500 (EST) 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 sLQl+j+Mgh1o for ; Wed, 8 Dec 2021 09:26:08 -0500 (EST) Received: from sin.source.kernel.org (sin.source.kernel.org [145.40.73.55]) by mm01.cs.columbia.edu (Postfix) with ESMTPS id 0AE744B12E for ; Wed, 8 Dec 2021 09:26:08 -0500 (EST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by sin.source.kernel.org (Postfix) with ESMTPS id CF4D2CE2047; Wed, 8 Dec 2021 14:26:02 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 08EE4C00446; Wed, 8 Dec 2021 14:26:01 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1638973561; bh=masfWCtDvMTnKHh0F/3FjTOXmIbksrroGUjVbK7y72w=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=s58d52vV0oOrQdckCJcANhAOiT8RUCWEkAhtlzgH5k+eK4zprIdGddpQCfvaPKqgO HKSmu6ikGAv3jt+HJjO0hA929QXmrflVDMFPLUR1dtQGaiuYt7uvOSo5WnIbY2MFvO XUD+v/S3IfCTbpDEKvGklLCSyq/Ebbb6FgI0FqHixeNyoRWoR1IybLiTYE+zb1wC1l KfdqXNAZPq6qZLs8WC/kgiauxlbpRlczcx+o58VRgA4UbLZwoyvOjcZ8ID6W3Fj7ca F3vO/h2oczwNPl4m9wRlTCMdJs4/fKhkfCAJ91Vc2jKHjCssnl4hswyasAc4Hp482K dgS0s3mqQW5NA== 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 1muxtP-00Amv3-2C; Wed, 08 Dec 2021 14:25:59 +0000 Date: Wed, 08 Dec 2021 14:25:58 +0000 Message-ID: <87czm718cp.wl-maz@kernel.org> From: Marc Zyngier To: Alexandru Elisei Subject: Re: [PATCH v2 3/4] KVM: arm64: Add KVM_ARM_VCPU_PMU_V3_SET_PMU attribute In-Reply-To: References: <20211206170223.309789-1-alexandru.elisei@arm.com> <20211206170223.309789-4-alexandru.elisei@arm.com> 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: alexandru.elisei@arm.com, reijiw@google.com, james.morse@arm.com, suzuki.poulose@arm.com, will@kernel.org, mark.rutland@arm.com, linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu, tglx@linutronix.de, mingo@redhat.com X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false Cc: mingo@redhat.com, tglx@linutronix.de, will@kernel.org, kvmarm@lists.cs.columbia.edu, linux-arm-kernel@lists.infradead.org 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 Wed, 08 Dec 2021 12:23:44 +0000, Alexandru Elisei wrote: > > This makes me wonder. Should KVM enforce having userspace either not > setting the PMU for any VCPU, either setting it for all VCPUs? I think this > would be a good idea and will reduce complexity in the long run. I also > don't see a use case for userspace choosing to set the PMU for a subset of > VCPUs, leaving the other VCPUs with the default behaviour. Indeed. As much as I'm happy to expose a PMU to a guest on an asymmetric system, I really do not want the asymmetry in the guest itself. So this should be an all or nothing behaviour. Thanks, M. -- 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 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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (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 80695C433FE for ; Wed, 8 Dec 2021 14:27:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:MIME-Version:References:In-Reply-To: Subject:Cc:To:From:Message-ID:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=wTv2CfxJx19x97+D8qUhgBDMdLQVix27gJ+/7Clbc7c=; b=1Xjn3hHTaME6Mf sA1mRIqYl+XTt9QwWKB1F3Zl4jfXQ98ihy9gUNyx1nRoAvKoHFdAXpue4llzWpz9s2NKxGrBGqNfL i+G6WQdJMVUUAN4RCw9AaFnsrJjSS9Pk99f5Z2v0fDnQCc54XgpvwOvkL2vrfAuw8BwvOWtqpnEnN EiT/ouCy0mlpw2ArF3aqsLFaPnhUIyO21Iz9YPbj+DdBAFOi6geMoZEMw6Rvca67K5D83V3ZfYL7G N+0zks25qODQGqNwJxWsW+uDOuG9MUCwgc1Ff+JqANYruzEPqpVY4Wg6T5rgi1N5mrip65Bl0VagU ydonGFfj1StWITJg/LdA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1muxtZ-00Cy3z-JF; Wed, 08 Dec 2021 14:26:09 +0000 Received: from sin.source.kernel.org ([145.40.73.55]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1muxtV-00Cy37-2T for linux-arm-kernel@lists.infradead.org; Wed, 08 Dec 2021 14:26:06 +0000 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by sin.source.kernel.org (Postfix) with ESMTPS id CF4D2CE2047; Wed, 8 Dec 2021 14:26:02 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 08EE4C00446; Wed, 8 Dec 2021 14:26:01 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1638973561; bh=masfWCtDvMTnKHh0F/3FjTOXmIbksrroGUjVbK7y72w=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=s58d52vV0oOrQdckCJcANhAOiT8RUCWEkAhtlzgH5k+eK4zprIdGddpQCfvaPKqgO HKSmu6ikGAv3jt+HJjO0hA929QXmrflVDMFPLUR1dtQGaiuYt7uvOSo5WnIbY2MFvO XUD+v/S3IfCTbpDEKvGklLCSyq/Ebbb6FgI0FqHixeNyoRWoR1IybLiTYE+zb1wC1l KfdqXNAZPq6qZLs8WC/kgiauxlbpRlczcx+o58VRgA4UbLZwoyvOjcZ8ID6W3Fj7ca F3vO/h2oczwNPl4m9wRlTCMdJs4/fKhkfCAJ91Vc2jKHjCssnl4hswyasAc4Hp482K dgS0s3mqQW5NA== 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 1muxtP-00Amv3-2C; Wed, 08 Dec 2021 14:25:59 +0000 Date: Wed, 08 Dec 2021 14:25:58 +0000 Message-ID: <87czm718cp.wl-maz@kernel.org> From: Marc Zyngier To: Alexandru Elisei Cc: Reiji Watanabe , james.morse@arm.com, suzuki.poulose@arm.com, will@kernel.org, mark.rutland@arm.com, linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu, tglx@linutronix.de, mingo@redhat.com Subject: Re: [PATCH v2 3/4] KVM: arm64: Add KVM_ARM_VCPU_PMU_V3_SET_PMU attribute In-Reply-To: References: <20211206170223.309789-1-alexandru.elisei@arm.com> <20211206170223.309789-4-alexandru.elisei@arm.com> 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: alexandru.elisei@arm.com, reijiw@google.com, james.morse@arm.com, suzuki.poulose@arm.com, will@kernel.org, mark.rutland@arm.com, linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu, tglx@linutronix.de, mingo@redhat.com X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20211208_062605_328862_94277B8E X-CRM114-Status: GOOD ( 16.83 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Wed, 08 Dec 2021 12:23:44 +0000, Alexandru Elisei wrote: > > This makes me wonder. Should KVM enforce having userspace either not > setting the PMU for any VCPU, either setting it for all VCPUs? I think this > would be a good idea and will reduce complexity in the long run. I also > don't see a use case for userspace choosing to set the PMU for a subset of > VCPUs, leaving the other VCPUs with the default behaviour. Indeed. As much as I'm happy to expose a PMU to a guest on an asymmetric system, I really do not want the asymmetry in the guest itself. So this should be an all or nothing behaviour. Thanks, M. -- Without deviation from the norm, progress is not possible. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel