From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=217.140.110.172 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1793025885; b=VMrUggvxbbmPmQqVeRNiMR585181nglUp8wVzb7LV6jfW8jnPDr8AbvxUFZxhulNh+1Q XTQvs4faVpkiwO9J92SjjBonIh+jjHtcz5Js/lVQPP/f6ezD06mdRAGaHT3zpDtFITgqM 0fugZyf0xtTQ9bewQUjqEu2wP29edyaZy+NGZh0Bq65hnFX/6W4o2CZbLPSx9c+Xbqgcf PcgXH5COP/gFjVe6BeXigtIFxmp5aMJ8klJkdkJ96vq9ts3/xoO2xSlLwNQz+68ZidSgE rEP/UewUxC/alRcNQh+N56iwASRhhv1c9lrclCS+Y8lhDmRzuZ6EJeYLLX+H2CdsACA== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793025885; h=DMARC-Filter:Received:Received:DKIM-Signature:From:To:Cc:Subject: Date:Message-ID:X-Mailer:In-Reply-To:References:MIME-Version: X-Developer-Signature:X-Developer-Key:Content-Transfer-Encoding; bh=GSEN1e/y0bwGfJJMQ9Hg+c2qcQyTslgLVny4UlJpg1o=; b=FE5yvtW01h1ElDPf7T55v+j5J5pe1+wcB7EbsOpjl1fD14vfHxQAci8AUKkc+6fi8TL8 ZW5/smDPe3fn47M3P6b/E2xXI4i4OSoVU3X5k2d3IO6nGkX3SOQX6G6ucFTYcm5mi0Oo3 WT2ko32KrUQDWsk3r2lu9IZCpnSKixzC3v/aPqALnMVWOqqp5jRhFC8RKSMeoXO1sMB1S V0qqrto/6p4nnLFc0ztrL84ckeZ00XrNCzkg6o3+tTD/jM20rcpw4kslRuu+31i72Ml6E g300TOppEcmaHfblbhRF+ONWPdeAgdx/FKEfEopuWW2fJIxPMgSQJPMiXhG1cVPJdXw== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass header.from=arm.com; spf=pass smtp.mailfrom=arm.com; dkim=pass header.d=arm.com header.i=@arm.com header.a=rsa-sha256 header.s=foss header.b=tc2dGiQf; arc=none smtp.remote-ip=217.140.110.172 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id A374B606A325 for ; Mon, 26 Oct 2026 14:44:44 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.2 smtp.subspace.kernel.org A374B606A325 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key, unprotected) header.d=arm.com header.i=@arm.com header.a=rsa-sha256 header.s=foss header.b=tc2dGiQf 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 B2BDC2720; Mon, 26 Oct 2026 07:44:40 -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 DD66B3F7B4; Mon, 26 Oct 2026 07:44:41 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1793025883; bh=lqK7uGIZ/jkYXTWUZmtWT+d67C2f5jU7aALBqK7r/3M=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=tc2dGiQfjBvRRqB83xDgLfT7zZBGGXCOJ/y/RYJCTy0uzkUQD6qVBVtFxLC4QFy0P QMrVMRfz9N6Tu4NyMPmo9maOMAYfFWxIMFkCTSiuBjeLbF1mhFwY1juF6ZmQIItpJq tEwHexZYWuH2RcdnrBz20PdT3yRc/HTIUBk41W2U= 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 1/3] KVM: arm64: pgtables: Set DBM attribute on writable Stage-2 PTEs Date: Mon, 26 Oct 2026 14:44:07 +0000 Message-ID: <20261026144413.441566-2-leo.bras@arm.com> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261026144413.441566-1-leo.bras@arm.com> References: <20261026144413.441566-1-leo.bras@arm.com> X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=3059; i=leo.bras@arm.com; h=from:subject; bh=lqK7uGIZ/jkYXTWUZmtWT+d67C2f5jU7aALBqK7r/3M=; b=owGbwMvMwCX2pizjszvTwvWMp9WSGLLup5u3z2By3Ri9qyTVOL/ze8XX5j+3r3DXf9jx7tzrd S86Vge/7ihlYRDjYpAVU2SRfTR/Fc/3KRlHrvxYADOHlQlkCAMXpwBMxLaWkeHF7OOelhsb3O52 xp20aLMsf1ic4ltp/X76thmVUZ+qODYyMtzMubvoaMYU0d3TzL5kXngj45Lzab/2Ln22Rc5PuM5 ObmUFAA== X-Developer-Key: i=leo.bras@arm.com; a=openpgp; fpr=36E6C95AE0F111CC5B6F4D2E688C33F8A0C5B0C5 Content-Transfer-Encoding: 8bit As a preparation to the introduction of HAFDBS-based features, set the DBM bit (along with S2AP[1]) to all writable PTEs. Also unset DBM and S2AP[1] when a PTE is made read-only again. DBM bit works as following: - If HAFDBS is disabled, DBM bit is ignored. - If HAFDBS is enabled, and DBM bit is set, a write to non-writable page can promote it's PTE to writable (S2AP[1]=1) without taking a fault. Since it's being set on writable and unset on read-only, it should cause no functional change. Signed-off-by: Leonardo Bras --- arch/arm64/include/asm/kvm_pgtable.h | 3 +++ arch/arm64/kvm/hyp/pgtable.c | 5 +++-- 2 files changed, 6 insertions(+), 2 deletions(-) diff --git a/arch/arm64/include/asm/kvm_pgtable.h b/arch/arm64/include/asm/kvm_pgtable.h index 41a8687938eb..37baa86d6fd8 100644 --- a/arch/arm64/include/asm/kvm_pgtable.h +++ b/arch/arm64/include/asm/kvm_pgtable.h @@ -91,14 +91,17 @@ typedef u64 kvm_pte_t; #define KVM_PTE_LEAF_ATTR_HI_S1_UXN BIT(54) #define KVM_PTE_LEAF_ATTR_HI_S1_PXN BIT(53) #define KVM_PTE_LEAF_ATTR_HI_S2_XN GENMASK(54, 53) +#define KVM_PTE_LEAF_ATTR_HI_S2_DBM BIT(51) + #define KVM_PTE_LEAF_ATTR_HI_S1_GP BIT(50) #define KVM_PTE_LEAF_ATTR_S2_PERMS (KVM_PTE_LEAF_ATTR_LO_S2_S2AP_R | \ KVM_PTE_LEAF_ATTR_LO_S2_S2AP_W | \ + KVM_PTE_LEAF_ATTR_HI_S2_DBM | \ KVM_PTE_LEAF_ATTR_HI_S2_XN) /* pKVM invalid pte encodings */ #define KVM_INVALID_PTE_TYPE_MASK GENMASK(63, 60) #define KVM_INVALID_PTE_ANNOT_MASK ~(KVM_PTE_VALID | \ diff --git a/arch/arm64/kvm/hyp/pgtable.c b/arch/arm64/kvm/hyp/pgtable.c index b74dd5ce1efd..8c2320c6a7f1 100644 --- a/arch/arm64/kvm/hyp/pgtable.c +++ b/arch/arm64/kvm/hyp/pgtable.c @@ -730,11 +730,11 @@ static int stage2_set_prot_attr(struct kvm_pgtable *pgt, enum kvm_pgtable_prot p if (prot & KVM_PGTABLE_PROT_R) attr |= KVM_PTE_LEAF_ATTR_LO_S2_S2AP_R; if (prot & KVM_PGTABLE_PROT_W) - attr |= KVM_PTE_LEAF_ATTR_LO_S2_S2AP_W; + attr |= KVM_PTE_LEAF_ATTR_HI_S2_DBM | KVM_PTE_LEAF_ATTR_LO_S2_S2AP_W; if (!kvm_lpa2_is_enabled()) attr |= FIELD_PREP(KVM_PTE_LEAF_ATTR_LO_S2_SH, sh); attr |= KVM_PTE_LEAF_ATTR_LO_S2_AF; @@ -1286,10 +1286,11 @@ static int stage2_update_leaf_attrs(struct kvm_pgtable *pgt, u64 addr, } int kvm_pgtable_stage2_wrprotect(struct kvm_pgtable *pgt, u64 addr, u64 size) { return stage2_update_leaf_attrs(pgt, addr, size, 0, + KVM_PTE_LEAF_ATTR_HI_S2_DBM | KVM_PTE_LEAF_ATTR_LO_S2_S2AP_W, NULL, NULL, KVM_PGTABLE_WALK_IGNORE_EAGAIN); } @@ -1366,11 +1367,11 @@ int kvm_pgtable_stage2_relax_perms(struct kvm_pgtable *pgt, u64 addr, if (prot & KVM_PGTABLE_PROT_R) set |= KVM_PTE_LEAF_ATTR_LO_S2_S2AP_R; if (prot & KVM_PGTABLE_PROT_W) - set |= KVM_PTE_LEAF_ATTR_LO_S2_S2AP_W; + set |= KVM_PTE_LEAF_ATTR_HI_S2_DBM | KVM_PTE_LEAF_ATTR_LO_S2_S2AP_W; if (prot & KVM_PGTABLE_PROT_X) { ret = stage2_set_xn_attr(prot, &xn); if (ret) return ret; -- 2.56.0