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 53663382368; Sun, 13 Sep 2026 09:09:31 +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=1789290574; cv=none; b=DVZ5GUSmit9tfrXmhngDgMh7R71YGaQbiFqywHs+F5sSovPrubfF7UTauKtOuIxDXoqDGEQxF712VXpGwN8qOIa2/WpExTlyyfh17wPuZVsjx2yY98QUXqk/5V1FA+Ou2AFjxga3/fVm9E2ZtiCl2wkS6+069NA8JdimBgi6QQc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789290574; c=relaxed/simple; bh=biB6FcaE7IhHa3WkVNRxXA3+g8lpuh4nuCTIk2KOshw=; h=Date:Message-ID:From:To:Cc:Subject:In-Reply-To:References: MIME-Version:Content-Type; b=Y1h3QW7dvuTDq7oz36rReG7XzgvpweDLHiKsZbAp/IVBGKfRSrg5cM59aczjRS8cJGK2macax9eBkssP6Vxo4bw0ki52G3s9+tVZjrujKzWGXOIIWOCZcl+qiqcYDMlHA5dUyfapHMKZED80WrW4kmgB5iuABzeha+crrsJyYR8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=EdhSwkpK; 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="EdhSwkpK" Received: by smtp.kernel.org (Postfix) with ESMTPSA id B9AD91F000FF; Sun, 13 Sep 2026 09:09:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1789290568; bh=ZTmi2IHALfHOiCA8eB+C5FrDQSC6nFg/q9Xm5fb4/JQ=; h=Date:From:To:Cc:Subject:In-Reply-To:References; b=EdhSwkpKJ1cRV6H6TwLDvi9cCY6J2W9/OperZcaGIUfH7etLYtRyBPzkdklJR+SzC Hsv/NpC+95NHhvj2dupvIXXAElt2vzfUQAvaz6O2bBIufiS9k2LfqcdFELDR+aDDff sSQO3RC/CETc+Cdv3PVBpfC49cPqh20bTRjjDwge5KdFhz3KDnwUx1e37fiVs4iZ9m eUl0CMsT+xGG23poOa9j2EoQGlva0Y6BZFeCe+Y9V+iXRhyFhgX5nbga2Kjt5h/U/p 80x3ny9LKEkGt4j6w1V/k+HlflTRMMhQ31Uf95V3PaEqfR4LRL0VSaNcu+Ci/qbjXC 9q0eSdAaHRbYg== 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 1x5gDG-00000008Fr0-1n0k; Sun, 13 Sep 2026 09:09:26 +0000 Date: Sun, 13 Sep 2026 10:09:25 +0100 Message-ID: <86a4pl7c1m.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 2/5] KVM: arm64: Add KVM_PGTABLE_PROT_DIRTY In-Reply-To: <20260901171558.2674031-3-leo.bras@arm.com> References: <20260901171558.2674031-1-leo.bras@arm.com> <20260901171558.2674031-3-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) Precedence: bulk X-Mailing-List: linux-kernel@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: 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 On Tue, 01 Sep 2026 18:15:53 +0100, Leonardo Bras wrote: > > Second step of changing the encoding for the Stage2 PTE descriptor, > introduce the concept of dirty page, so we can have a writable but not > dirty (WC) page, and a writable and dirty (WD) page. Why should we care about *setting* the dirty bit in the PTE? Under what circumstance do we want to establish a mapping as being dirty? The whole point of DBM is to only set something dirty when it is written to, and this patch breaks this invariant. Maybe you have a good reason to do so, but that's not explained. M. -- Without deviation from the norm, progress is not possible.