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 B3B79C54FD2 for ; Thu, 30 Jul 2026 03:22:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:In-Reply-To:Content-Type: MIME-Version:References:Message-ID:Subject:Cc:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=B3m6klE7M6GPyf33UUyOsEdcuYBciPrJm1ED2GD56QU=; b=LlgCd7uqON+fWLlAd45WeFtDjG RyzImmOuyOH5xAIVF9v5FY4hftR1E2gjEkybHs3iXTfhbM+rkGHN6jjjxdHQsLxnWRQbUeZTLujKF TuWwrM08R/mkHhNohF0s8wYjJqGOQJAx5A7mc/72D/q406Ks0HtBGDXbtWYmHS0hikWUrNP4p6Lco v8sxKIXYNK+OOq/J8dDQPwIyHseQYN66iomvDRCtBaqS28fRke+pwXdKJ1V4RqQO/WdT7u0hA7Jb3 /TrVX60NTkZOLPA9v9H0Ds6vopu8ohIbGgZOPvarS6BRMLBW90tcRz8ZoKBMsEjP7DiWa0FriPulD QLE2nGIg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1wpHM7-00000009PNk-0gJj; Thu, 30 Jul 2026 03:22:47 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1wpHM4-00000009PMq-0EBe for linux-arm-kernel@lists.infradead.org; Thu, 30 Jul 2026 03:22:45 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id E7E891684; Wed, 29 Jul 2026 20:22:36 -0700 (PDT) Received: from localhost (a079125.arm.com [10.164.21.43]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 451723F763; Wed, 29 Jul 2026 20:22:40 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1785381761; bh=/1yTzYFGg3pV1usAbAUtPbtP+HA7uKNwPQmps+iLHVA=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=WC5qUcaNXp7YRQUQva+KqAzlEwiNFkhj7vRPDnylSaQJ9cC9iMAcGpdkb6rq9cNiF /OjqhnNkYflxnuK1FVgGTmKpcdsMQAvdg00NrAI4KnmgAfYsOjtXjolU8Rma8WQzmS BYW4vmCoGUyIU7evJ61g8aN7ThcGiL3Myb5xUHL4= Date: Thu, 30 Jul 2026 08:52:37 +0530 From: Linu Cherian To: Mostafa Saleh Cc: linux-kernel@vger.kernel.org, kvmarm@lists.linux.dev, linux-arm-kernel@lists.infradead.org, maz@kernel.org, oupton@kernel.org, seiden@linux.ibm.com, joey.gouly@arm.com, suzuki.poulose@arm.com, yuzenghui@huawei.com, catalin.marinas@arm.com, will@kernel.org, vdonnefort@google.com, tabba@google.com, sebastianene@google.com, keirf@google.com Subject: Re: [RFC PATCH v2 0/2] KVM: arm64: Add support for BBM level 3 Message-ID: References: <20260723182140.4025575-1-smostafa@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260723182140.4025575-1-smostafa@google.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260729_202244_201867_8EB5F63E X-CRM114-Status: GOOD ( 15.38 ) 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: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Hi, On Thu, Jul 23, 2026 at 06:21:38PM +0000, Mostafa Saleh wrote: > This patch series adds support for BBM level 3 to KVM pgtable, it > depends on [1] > > Changes from v1: > https://lore.kernel.org/all/20260717130901.2239134-1-smostafa@google.com/ > - Limit BBML3 to systems with FWB and DIC and remove race check. > > Motivation > ========== > I have been looking into this for the context of: > - Page table sharing between the host CPU stage-2 and the SMMUv3 for > protected KVM. > - Use the pagtable code to populate SMMUv3 stage-2 shadowed > page table [2] > > However, BBM level 3 is still useful for CPU only operations as it > avoids intermediately breaking translation. > > Design > ====== > Some of the conditions that BBM level 3 will be useful in (RWHZWS): > 1) A change to a PTE memory type, shareability, cacheability or OA Could you please clarify how BBM level 3 is helping this particular scenario ? This is supposed to be a case where break before make is required. Thanks, Linu Cherian.