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 F2A8138B7BA for ; Tue, 23 Jun 2026 18:42:06 +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=1782240127; cv=none; b=MX6eTp3XWybdwd1o5PytDf4zu/DEw9+uT3h8RMNWqeBVEJguLrj66rAl6BMsCwwaLL+Kks8y4DZPL2G1qRGdbJ0O3CJh2nsO+UpO2JXOHaMxb9xarjEnP6UUWwSl53XLd3IEsqW+dw25AhSzMk+Hk/b0A26M5Z0qTCdcuWPmwC0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782240127; c=relaxed/simple; bh=z3jF6MPLiA62+2y2tpy7zIz3d63t/9m0jF69QjIqbYQ=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=rYz/R4GIN4Sv3hwyVCmKJ3YHFeqRBrlF13VV3L5R00DvcFuTeQNQYdlCRfuct1c23iqbQeok0k27QUNwnT3vrIWEVV+K+7Bs7NuHKeduI7Temn6FDq4ejFzdA2s+da3V1I/Xy0jx2k+lJ5eMg3HnR8Q2vLYk1+yt2mf/XI3ABBg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=jzxs6LI5; 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="jzxs6LI5" Received: by smtp.kernel.org (Postfix) with ESMTPSA id C065C1F00ADE; Tue, 23 Jun 2026 18:42:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1782240126; bh=T+YhAnEJPl0Ho6vj8x0xFF0JruUyJxZJ7ih1hHx69v0=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=jzxs6LI51WsEwAmFJ+8M1/5XdGHcC32O9pcbAubw3umgXLtUX/08OOZWlBMi/w4lF oglPL/PK3IFZrhMYpdWQ2EmArBGOunwJ6wiDIcic/snqJnqO9ppoIpHyJpCMII43YE PB0/vhcMgIQfuka8/y0i3eqBDAnf399WKDs6Q2SnI2PzbC0iXBcMmLI8aGNNNSbjoO 0QuRTLk1ShOCMNtDQNpn4Ia4FUaarBZqRZn3h+Xg1Cm4V/maY96xN1a9TuPJsrJfzm bcurj48quCTlBXW8B7Prznf4Dj07RevFoN65h5ytpfxgRzu8wGW80M5wZJ3xCdaKT0 OytbVAKxb6Qvg== From: Oliver Upton To: kvmarm@lists.linux.dev Cc: Marc Zyngier , Joey Gouly , Suzuki K Poulose , Zenghui Yu , Wei-Lin Chang , Steffen Eiden , Oliver Upton Subject: [PATCH 08/22] KVM: arm64: nv: Treat DBM as writable at stage-2 Date: Tue, 23 Jun 2026 11:41:47 -0700 Message-ID: <20260623184201.1518871-9-oupton@kernel.org> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20260623184201.1518871-1-oupton@kernel.org> References: <20260623184201.1518871-1-oupton@kernel.org> Precedence: bulk X-Mailing-List: kvmarm@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit When using direct permissions, the DBM bit has the effect of granting the write permission. And, depending on the access, it could grant write permission without a dirty state update. Signed-off-by: Oliver Upton --- arch/arm64/include/asm/kvm_pgtable.h | 1 + arch/arm64/kvm/nested.c | 11 +++++++++++ 2 files changed, 12 insertions(+) diff --git a/arch/arm64/include/asm/kvm_pgtable.h b/arch/arm64/include/asm/kvm_pgtable.h index 22aeb2ed18d1..6ae36973686c 100644 --- a/arch/arm64/include/asm/kvm_pgtable.h +++ b/arch/arm64/include/asm/kvm_pgtable.h @@ -94,6 +94,7 @@ typedef u64 kvm_pte_t; #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) diff --git a/arch/arm64/kvm/nested.c b/arch/arm64/kvm/nested.c index e5a407fc0880..4f13f37e560b 100644 --- a/arch/arm64/kvm/nested.c +++ b/arch/arm64/kvm/nested.c @@ -305,6 +305,17 @@ static void compute_s2_permissions(struct kvm_vcpu *vcpu, struct s2_walk_info *w break; } + /* + * Descriptors with the DBM bit set while hardware dirty state are + * considered writable, even though certain accesses (like AT instructions) + * don't actually update the dirty state. + * + * Assume that walk_nestd_s2_pgd() made the necessary descriptor updates + * for the access and just treat DBM as writable here. + */ + if (wi->hd && ws->desc & KVM_PTE_LEAF_ATTR_HI_S2_DBM) + s2ap |= BIT(1); + trans->readable = s2ap & BIT(0); trans->writable = s2ap & BIT(1); -- 2.47.3