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 306F0C433F5 for ; Wed, 8 Dec 2021 16:21:54 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id B9F914B17B; Wed, 8 Dec 2021 11:21:53 -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 63zt03KzkBRj; Wed, 8 Dec 2021 11:21:52 -0500 (EST) Received: from mm01.cs.columbia.edu (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id C1EA34B17D; Wed, 8 Dec 2021 11:21:52 -0500 (EST) Received: from localhost (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id 2BEDF4B10B for ; Wed, 8 Dec 2021 11:21:52 -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 KiNvbSM7x85J for ; Wed, 8 Dec 2021 11:21:51 -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 B642D4B102 for ; Wed, 8 Dec 2021 11:21:50 -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 62C0ECE2213; Wed, 8 Dec 2021 16:21:47 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 90079C00446; Wed, 8 Dec 2021 16:21:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1638980505; bh=euvU/ikhRj94462H2iPRt5sqM867Jp+fWa+5bBnCcyY=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=rmTZKlO7MbHO7ozUwKDdR+AD7ITDbOVHZBseyzoVvZ9JAaspxivLdVYcAYbvmc6YT LfCsq1CbqvjdklWLA66MaM4jRdZzT2RCvu9BP5DdDEag8Mkqa/YIKim8FAHIqIgrLC HakydHPR2OETM7W+8EtE3yyDDx3oywstR6hnK0r6hXKBQi4vaItw6CZxuJSxhAX5uE pBza1dnQAO3AeHxXomHE1x0a6qaPOVXnks/sIGopFeu+l34BEeGsnFDahCXxVXQ0F/ 7LAifIk6VNXS4BDNIGooJrNrt0Gh2YZ/MR9o6+zq6N9OZllCi92d3bOQPmubSGEa3K 20zOua97H2RXQ== 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 1muzhP-00AoeE-I2; Wed, 08 Dec 2021 16:21:43 +0000 Date: Wed, 08 Dec 2021 16:21:43 +0000 Message-ID: <878rwv12zs.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> <87czm718cp.wl-maz@kernel.org> <87bl1r14po.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: 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 16:11:13 +0000, Alexandru Elisei wrote: > > > On the contrary, I am *very* happy to limit a VM to a single PMU (and > > thus CPU) type on these systems. Really. > > Ok, so any kind of asymmetry is unacceptable. > > Accepted behaviour: > > 1. If userspace sets PMU for one VCPU, then *all* other VCPUs must > have a PMU set, and furthermore, it must be the same PMU as the > first VCPU, > > or > > 2. If userspace has initialized a PMU (via > KVM_ARM_VCPU_PMU_V3_CTRL(KVM_ARM_VCPU_PMU_V3_INIT)) without setting > a PMU, then it is forbidden for userspace to set a PMU for the other > VCPUs. > > Is that what you had in mind? Exactly. This sidesteps any sort of odd behaviour by forcing userspace to pick a side. 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