From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 DF1151D68D for ; Mon, 13 Nov 2023 12:20:13 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="aimS3cHA" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 536E4C433C8; Mon, 13 Nov 2023 12:20:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1699878013; bh=8DnSkOb2AZ9fL9uTr796IMBrSVSTDYiefe5OpwJrUw4=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=aimS3cHAXEdjzcS+iUYlaGgUQhAwUg8qvNly0bS7Rc5I0hOF8ArW8kB3eC7VvE3WS ZxIUBXx3mygCO/cZ3NwWFGIobN84hqGvWW6iZHn4s5u2FXamwzQKzHemZWffTAuqOc dpe1Dfk7lquC7iwaDdmvm5gh9NbyQIJPIjRWJadJhYBsa8tlMjqIT2b4spYxXZbrP5 hBVHE7qCfR2L3OK/oUZY8hkd0hEyYWyHMfFPvF+0QogRIdlZmq7/pzb73tRGCyBQPR C57GoOBQ47wuk+bD8siEYsaS2ZUBOWIPP2ZZibLcRSsFzqR9R0qQEZQFfcuicg6S5c guiDfBhBV25Cg== 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 4.95) (envelope-from ) id 1r2VvG-00Cfpl-Vg; Mon, 13 Nov 2023 12:20:11 +0000 Date: Mon, 13 Nov 2023 12:20:10 +0000 Message-ID: <868r7126bp.wl-maz@kernel.org> From: Marc Zyngier To: Ryan Roberts Cc: Ard Biesheuvel , Ard Biesheuvel , Will Deacon , Catalin Marinas , Oliver Upton , Mark Rutland , Anshuman Khandual , Kees Cook , Joey Gouly , Suzuki K Poulose , James Morse , Zenghui Yu , linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev Subject: Re: [RFC PATCH v1 0/3] Update tlb invalidation routines for FEAT_LPA2 In-Reply-To: <3800df70-73f2-44b7-a6ed-15ec0bd63f5f@arm.com> References: <20231027115634.1432154-1-ryan.roberts@arm.com> <3800df70-73f2-44b7-a6ed-15ec0bd63f5f@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/29.1 (aarch64-unknown-linux-gnu) MULE/6.0 (HANACHIRUSATO) Precedence: bulk X-Mailing-List: kvmarm@lists.linux.dev 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: ryan.roberts@arm.com, ardb@google.com, ardb@kernel.org, will@kernel.org, catalin.marinas@arm.com, oliver.upton@linux.dev, mark.rutland@arm.com, anshuman.khandual@arm.com, keescook@chromium.org, joey.gouly@arm.com, suzuki.poulose@arm.com, james.morse@arm.com, yuzenghui@huawei.com, linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false On Mon, 13 Nov 2023 11:55:01 +0000, Ryan Roberts wrote: > > On 27/10/2023 12:56, Ryan Roberts wrote: > > Hi All, > > > > As raised yesterday against Ard's LPA2 series [1], we need to address the TLBI > > changes to properly support LPA2 before Ard's changes get merged. So far those > > changes have been part of my KVM LPA2 series [2]. So this is an attempt to split > > the TLBI changes to make them independent. The idea is that this series would go > > in first, then Ard's and the rest of my series can race eachother and it doesn't > > really matter who wins. > > > > I've attempted to address all of Marc's feedback against the versions of these > > patches posted at [2], including adding benchmark data (see patch 1). Although > > if people are still nervous that this could regress non-lpa2 performance in some > > cases, I could rework so that there are lpa2 and non-lpa2 variants of > > __flush_tlb_range_op(), and the correct version is chosen at the higher level > > (based on lpa2_is_enabled() / kvm_lpa2_is_enabled()). > > > > It turns out that we won't be able to key LPA2 usage off the same static key for > > both the kernel and kvm usage because the kernel usage additionally depends on > > CONFIG_ARM64_LPA2 being enabled. So I've introduced 2 stub functions > > (lpa2_is_enabled() and kvm_lpa2_is_enabled()) to advertise it. Ard already > > defines and implements lpa2_is_enabled() in his series, so there will be a minor > > conflict to resolve there. I plan to define kvm_lpa2_is_enabled() to be the > > static key for kvm in my series. Marc, would you be happy with this approach? > > > > Anyway, I wanted to put this out there as an RFC. If we are happy with it, then > > I'll re-post on 6.7-rc1. > > Marc, All, > > I polite bump; I never heard back on this. I'm planning to post my LPA2/KVM > series on top of v6.7-rc1 in the next day or 2. By default, these 3 patches will > be the first 3 of the series. But if you have an issue with the approach it > would be good to work out an alternative plan to avoid wasting effort preparing > the series. No specific concern on the approach. Having a static-key for the KVM side is good, and the uplift on the range stuff seems compelling. Thanks, M. -- Without deviation from the norm, progress is not possible.