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 5D847C79FB6 for ; Sat, 12 Sep 2026 12:24:26 +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:Content-Type:MIME-Version: References:In-Reply-To:Subject:Cc:To:From:Message-ID: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=MwPTM//i6FM3Z7OaQNRWjBG3Y4UxlxBNK7ODAKlkKWg=; b=H94v3b78py8AQYXgHX7XHwHXY3 v0E5SogLjT4kiuAKO5sKIWOaBwmo+iCpoo53JQYzzGkyQEeNG+yCPoDhWWuh4/fyLXjWeIn9W825l t8IqqyRkk52Bog+xNmUYkk8/wSK06q9DCTkWFx3+wJv15zX0YfQQVGhBfq5RZJM0fgv9AEzm7WzBA si6+CFZjVWLxdfX794gmxev39PdxG1+J1feIUy5Hckc8eYYVWvr6/1TIMUQGarsmvd0qyQzYYPGLr D/QrZDtaxa5me8v3GyNs9BVjbMyCGKwAELGe4SCdfUvC0IFds/lvNz5a2uXiIs/l25iwmQqF3RG/q EU9d4Bog==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1x5MmG-00000000rNe-0ysQ; Sat, 12 Sep 2026 12:24:16 +0000 Received: from tor.source.kernel.org ([172.105.4.254]) by bombadil.infradead.org with esmtps (Exim 4.99.1 #2 (Red Hat Linux)) id 1x5MmE-00000000rNY-3hhG for linux-arm-kernel@lists.infradead.org; Sat, 12 Sep 2026 12:24:14 +0000 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by tor.source.kernel.org (Postfix) with ESMTP id 0D13060236; Sat, 12 Sep 2026 12:24:14 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id B555D1F00893; Sat, 12 Sep 2026 12:24:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1789215853; bh=MwPTM//i6FM3Z7OaQNRWjBG3Y4UxlxBNK7ODAKlkKWg=; h=Date:From:To:Cc:Subject:In-Reply-To:References; b=cIbLyp98zvlcM1ra/sApj7D5Ra/6pQM2nU+oVG5Tsb5uJ3SKMBT/tuZCSQCdQp8n7 aqs57vol6nPjRO1NOgCYWMTTO1ZlhIhiJhbCShxBfENUECwiV4pGaOB+xJpjPEFGu4 PYQoq0OGPPQx7VF4xC9ILBGRcv5wgtrINpiUYXeeEityxgS/7QNXUb+P82Duj8gcSi HznxnT3ASo5igdQnL1ZascS/WA6EijM5Nmxf5x9JlMu/M8thwM/vTIW0GaH+SgvIRl TKgxpBbtcxHfiA0QsWT44H+qTBAS0RSLdUHndxRL3VLQeNiQOiOT01yZWVmjC2cTaG ie6jGnn4IDLbA== 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 1x5MmB-000000085Sd-2Ra0; Sat, 12 Sep 2026 12:24:11 +0000 Date: Sat, 12 Sep 2026 13:24:11 +0100 Message-ID: <86cxui7j4k.wl-maz@kernel.org> From: Marc Zyngier To: Leonardo Bras Cc: Oliver Upton , Fuad Tabba , Joey Gouly , Steffen Eiden , Suzuki K Poulose , Zenghui Yu , Catalin Marinas , Will Deacon , Mark Rutland , Raghavendra Rao Ananta , Tian Zheng , linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev, linux-kernel@vger.kernel.org Subject: Re: [RFC PATCH 0/5] KVM: arm64: New PTE dirty-page encoding, HAFDBS new usage In-Reply-To: <20260901171558.2674031-1-leo.bras@arm.com> References: <20260901171558.2674031-1-leo.bras@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/30.1 (aarch64-unknown-linux-gnu) MULE/6.0 (HANACHIRUSATO) 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: leo.bras@arm.com, oupton@kernel.org, fuad.tabba@linux.dev, joey.gouly@arm.com, seiden@linux.ibm.com, suzuki.poulose@arm.com, yuzenghui@huawei.com, catalin.marinas@arm.com, will@kernel.org, mark.rutland@arm.com, rananta@google.com, zhengtian10@huawei.com, linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev, linux-kernel@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 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 On Tue, 01 Sep 2026 18:15:51 +0100, Leonardo Bras wrote: > > This series have 2 main goals: > > 1 - Patches #1,#2,#3 : Change the PTE descriptor to use WD/WC/RO encodings > making use of the DBM bit, adapting all usages, and What are WD and WC? I can sort of guess that this is write-dirty and write clean, but that's not exactly obvious. More importantly, you don't even explain *why* anything needs changing... > 2 - Patches #4,#5 are an RFC on using HAFDBS on a guest to avoid resetting > all PTEs to WC when dirty-logging starts, speeding-up startup. > > (1) will also introduce a new walker for cleaning the dirty-bit, which will > clear the DBM bit if it's a block mapping (hugepage). This is needed as on > lazy-splitting we need to fault a write so we can do the lazy splitting. > This is needed for both the next patches, and for HDBSS & HACDBS > enablement. Again, this is incredibly opaque to the reviewer. What is the problem you are trying to solve? This is what a cover letter is for. M. -- Without deviation from the norm, progress is not possible.