From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 2B1E33BB135; Tue, 7 Jul 2026 09:41:37 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783417298; cv=none; b=JnLcDyxJ2ms8aZ9Tp89uSvEmUajhEp+upwqEp8paFwUnXQugAY3kG2HLjsgK5t9ZWtDjBYR8INPCKPPXBbR5VeIDYVEAdRF9bUYDhUKcr8cGU1IFmFU3W9Yu03NIk+QGACnpMZB87MtQTwHTzAH18PQW0CIXHNNDqnHGIM+iLp4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783417298; c=relaxed/simple; bh=C2QbuCacjTPszwp8554QdsIjQ5yl4pwtYb4k2JRAQzY=; h=Date:Message-ID:From:To:Cc:Subject:In-Reply-To:References: MIME-Version:Content-Type; b=W/TyKib9JT32zF+c7lr+Hb4NyHcwXKpCc7sqlKUcl32LnMxmACn0he2Sx81nC8autuQzjh2ADqu9iT1xuAPlEqid1tuQW/yA+7f9m3yig51+4Vrt7wNQA7fP8iFldmveLowgGKdA41zgddjyvOTI65lsvEANWMHMSwV2WTbgxas= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=QfUUXnPj; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="QfUUXnPj" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 0054E1F000E9; Tue, 7 Jul 2026 09:41:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1783417297; bh=edq9/jN03tElaw6k+IpT0Yftpb/niEsz9qEsQVfwHiM=; h=Date:From:To:Cc:Subject:In-Reply-To:References; b=QfUUXnPj15wViNjXPs9pgLJxKLcvzihhyeuHVy4vGQCrz2E0tXuQaFrhHxHojpPnY VochgGMZmL24b+nFmBaH7AlT+eqcZc67eWDCE/mWMI8b9o75cyUarVZeOGsGq9Wx32 SA5MXJYpcaHdep/0UVXHAU/YkGhArhBHAuCLWGEMO82dfHUmOdTzfUIvsr+vlE/lKj bsBgRetjbjUFLoO9wW1SouScNkN4w53t+4BicQvI2GUe/YQfmmpXLOPjQEGRhVYZFf wSCeq0FZFUQiX32OXwx2OnBXymuO8MVhf0yM8is5OEnM6Gw5jwX4q0cA/82XZKZdfw eCC5ZlDxjZcEw== Received: from sofa.misterjones.org ([185.219.108.64] helo=goblin-girl.misterjones.org) by disco-boy.misterjones.org with esmtpsa (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.98.2) (envelope-from ) id 1wh2J4-00000002KzE-30Of; Tue, 07 Jul 2026 09:41:34 +0000 Date: Tue, 07 Jul 2026 10:41:34 +0100 Message-ID: <868q7np25t.wl-maz@kernel.org> From: Marc Zyngier To: Oliver Upton Cc: Akihiko Odaki , Joey Gouly , Suzuki K Poulose , Zenghui Yu , Catalin Marinas , Will Deacon , Kees Cook , "Gustavo A. R. Silva" , Paolo Bonzini , Jonathan Corbet , Shuah Khan , Shuah Khan , linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev, linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org, devel@daynix.com, kvm@vger.kernel.org, linux-doc@vger.kernel.org, linux-kselftest@vger.kernel.org Subject: Re: [PATCH v8 0/7] KVM: arm64: PMU: Use multiple host PMUs In-Reply-To: References: <20260706-hybrid-v8-0-de459617b59d@rsg.ci.i.u-tokyo.ac.jp> <86bjcjp6x1.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/30.1 (aarch64-unknown-linux-gnu) MULE/6.0 (HANACHIRUSATO) Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: 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: oupton@kernel.org, odaki@rsg.ci.i.u-tokyo.ac.jp, joey.gouly@arm.com, suzuki.poulose@arm.com, yuzenghui@huawei.com, catalin.marinas@arm.com, will@kernel.org, kees@kernel.org, gustavoars@kernel.org, pbonzini@redhat.com, corbet@lwn.net, shuah@kernel.org, skhan@linuxfoundation.org, linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev, linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org, devel@daynix.com, kvm@vger.kernel.org, linux-doc@vger.kernel.org, linux-kselftest@vger.kernel.org X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false On Tue, 07 Jul 2026 09:10:17 +0100, Oliver Upton wrote: > > On Tue, Jul 07, 2026 at 08:58:50AM +0100, Marc Zyngier wrote: > > On Mon, 06 Jul 2026 19:28:20 +0100, > > Oliver Upton wrote: > > > > > > On Mon, Jul 06, 2026 at 07:03:23PM +0900, Akihiko Odaki wrote: > > > > Akihiko Odaki (7): > > > > KVM: arm64: Disallow vPMU when pPMUs do not cover all CPUs > > > > KVM: arm64: PMU: Protect the list of PMUs with RCU > > > > KVM: arm64: PMU: Pass the pPMU to kvm_map_pmu_event() > > > > KVM: arm64: PMU: Pass the target CPU to kvm_pmu_probe_armpmu() > > > > KVM: arm64: PMU: Implement fixed-counters-only emulation > > > > KVM: arm64: PMU: Introduce FIXED_COUNTERS_ONLY > > > > KVM: arm64: selftests: Test PMU_V3_FIXED_COUNTERS_ONLY > > > > > > Thanks for respinning the series, I left some comments. I'd really like > > > to get this feature picked up, hope you have cycles to work on it soon. > > > > > > FWIW, we're considering adding a new vCPU feature flag to deprecate all > > > the ugliness of the old PMUv3 UAPI. I'm tempted to say that the > > > FIXED_COUNTERS_ONLY feature is conditioned on the new feature flag... > > > > It'd be good to have a strawman proposal on the list if we are going > > to change add a new API, specially if this is likely to gate new code. > > > > Patch 1 [*] of the series I linked does exactly this, no? Needs some Ah, I overlooked that, apologies. > attention like a KVM_CAP to make the bit discoverable by the VMM but > gets the general idea across. Not sure that's the ideal approach, specially in the light of this "multiple PMU" series. This "strict" API mandates the selection of a PMU (singular), while this stuff is the exact opposite (grab all the possible PMUs). M. -- Without deviation from the norm, progress is not possible.