From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1) server-digest SHA256) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 5BC6E606A32A for ; Mon, 26 Oct 2026 14:45:06 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=lists.infradead.org header.i=@lists.infradead.org header.a=rsa-sha256 header.s=bombadil.20210309 header.b=3CJiuDfB; dkim=pass (1024-bit key, unprotected) header.d=arm.com header.i=@arm.com header.a=rsa-sha256 header.s=foss header.b=cc641w2U 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-Transfer-Encoding: MIME-Version:Message-ID:Date:Subject:Cc:To:From:Reply-To:Content-Type: Content-ID:Content-Description:Resent-Date:Resent-From:Resent-Sender: Resent-To:Resent-Cc:Resent-Message-ID:In-Reply-To:References: List-Unsubscribe-Post:List-Owner; bh=2bC/tKvsMyQSFyWd/4grWajRGenpXtC7/e5rOkNlwlE=; b=3CJiuDfB4i/G5E5ZMZos7yn4Nl 1dOP9VLEWQeNadjB7Myqcx3/aeufB60NQQxw+/3MU3XK/Oop8xPvm8sPeaih3MAnZmSLAe/Nhn0w3 GWawIZXHLwyOcT5xYmuD1CJJnbf9tbpbwz0A5FaRvZYwnjQnVlIf9qZA+6/SzVGbueGA3i4XyVZ1K x6Yrdy6q+bcPJG7PydhDg6X0r/6EevdzSNWPmvJtqHiFERPgPTFs0Otp8lkwaI85B0yN72VIc0Oxp LTc/1AOXVGqorfHyIqb3NRuT1IHHYuZBZU4q5raTeZQZj6pwN5VfW/oXgsbOzRMrZkVxDXWS+KKe+ 8QtDLMqg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.100.1 #2 (Red Hat Linux)) id 1xLLwQ-00000002gpa-2jyB; Mon, 26 Oct 2026 14:44:50 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.100.1 #2 (Red Hat Linux)) id 1xLLwM-00000002gnZ-46Gi for linux-arm-kernel@lists.infradead.org; Mon, 26 Oct 2026 14:44:48 +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 6D1F415A1; Mon, 26 Oct 2026 07:44:38 -0700 (PDT) Received: from LeoBrasDK.cambridge.arm.com (LeoBrasDK.cambridge.arm.com [10.2.212.21]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 932E83F7B4; Mon, 26 Oct 2026 07:44:39 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1793025881; bh=cXwGQ1sgxxKZyhdDrXpdQtNttNvD0RVFexoJ9R9VXl8=; h=From:To:Cc:Subject:Date:From; b=cc641w2UwlCKZjaZ6pVm4urYV48alptH2J9aWv5cKo5Wo1XqBvDykrSj2aRAF1H9i 5sGR5B/F9mKusRhXjgKIwz+SfGLvQJp9Dzctg82Pwl7Yp9JDNQ3UD0zpTgP0sbOIKI y/kJZBx0ZBNZF5QpiXnZvHAD6GEi0iCyS14f6D4k= From: Leonardo Bras To: Oliver Upton , Marc Zyngier , Fuad Tabba , Joey Gouly , Steffen Eiden , Suzuki K Poulose , Zenghui Yu , Catalin Marinas , Will Deacon , Mark Rutland , Leonardo Bras , Raghavendra Rao Ananta , Tian Zheng Cc: linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev, linux-kernel@vger.kernel.org Subject: [RFC PATCH v2 0/3] Set DBM bit on writable pages Date: Mon, 26 Oct 2026 14:44:06 +0000 Message-ID: <20261026144413.441566-1-leo.bras@arm.com> X-Mailer: git-send-email 2.56.0 X-Archived-By: MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=2136; i=leo.bras@arm.com; h=from:subject; bh=cXwGQ1sgxxKZyhdDrXpdQtNttNvD0RVFexoJ9R9VXl8=; b=owGbwMvMwCX2pizjszvTwvWMp9WSGLLupxsaJqiuV//2b+8U5p99kl2hzS61uzMNn29+8EIr9 PfZwLlhHaUsDGJcDLJiiiyyj+av4vk+JePIlR8LYOawMoEMYeDiFICJ/F7IyDDpjlbE/mvLLW3a F9sVzTFn1cmZdlVw/gepVAshs0UTFu5jZFjdof9mzTn9Loub/25bWaR+uPTkvOrnlX+bt+6J8NG de4MLAA== X-Developer-Key: i=leo.bras@arm.com; a=openpgp; fpr=36E6C95AE0F111CC5B6F4D2E688C33F8A0C5B0C5 Content-Transfer-Encoding: 8bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20261026_074447_102795_AFEF4BE7 X-CRM114-Status: GOOD ( 14.32 ) X-Spam-Score: -4.4 (----) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" X-Spam-Status: No, score=-14.2 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=ham autolearn_force=no version=4.0.1 X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 When HAFDBS is enabled (VTCR_EL2.{HA,HD}={1,1}), having a DBM bit allows hardware to promote a non-writable page to writable by setting (S2AP[1]=1), without having to take a fault. The reason for this patchset is to add the DBM bit when setting-up writable pages, so the code is prepared for future patches that make use of HDBSS/HACDBS to accelerate dirty-tracking. Write-bit detection still happens based only in S2AP[1], so no change in that aspect. Having DBM set on block entries is undesired, as we benefit from the first fault for splitting it in PAGE_SIZE entries, which is the granularity used to track the dirty pages in KVM. So introduce a new walker that, on top of clearing S2AP[1] for every entry, also clear DBM for block entries. Also introduce a new VCPU request to reload Stage2, as it will be needed on future HDBSS/HAFDBS patchsets. Please let me know of what do you think! Changes since RFCv1: - Dropped patch #5 on enabling HAFDBS on non-dirty-tracking guests, as it proved to be counter-productive on wrprotect, contrary to expectations - No more moving writable-bit to DBM. That does not seem to be the intended use. It makes sense and it's easier to convert code to new DBM approach. - No new PROT_DIRTY, so drop patch #2 - Tried adding a PROT_DBM, but does not seem necessary to fault a page as writable-clean. - KVM_REQ_RELOAD_STAGE2 now depends on VHE, as it already reloads Stage2 on guest entry otherwise. Link: https://lore.kernel.org/all/20260901171558.2674031-1-leo.bras@arm.com/ Thanks! Leo Leonardo Bras (3): KVM: arm64: pgtables: Set DBM attribute on writable Stage-2 PTEs KVM: arm64: Introduce a dedicated walker for stage2 write-protect KVM: arm64: Add KVM_REQ_RELOAD_STAGE2 arch/arm64/include/asm/kvm_host.h | 2 ++ arch/arm64/include/asm/kvm_pgtable.h | 3 +++ arch/arm64/kvm/arm.c | 10 ++++++++++ arch/arm64/kvm/hyp/pgtable.c | 30 ++++++++++++++++++++++------ 4 files changed, 39 insertions(+), 6 deletions(-) base-commit: c03c1a14507dfaf8b856c2608f9ac216021fc222 -- 2.56.0