From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 7D8B43E8C61; Tue, 31 Mar 2026 14:14:03 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774966445; cv=none; b=OVlyxgwMpig51UMMkrY0QygV4mk60tMxPwCaiv8SlSGYK49nonQlUJ3Hl49rmlW5pGzF7kj753pYqYV9Lr5NWSLXLmKg2N1DrdEsAiGe5j0ZPFcz1d72H6m3SEHxI3NKWf6QZFdBKPsRoYP7uW6Hq+dTjF5YdHD+fk6TNk/tpy8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774966445; c=relaxed/simple; bh=0WokdVZGVQOySMRtOFuViCjuFlNJiqco1s6MePa8OP0=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type:Content-Disposition; b=UwJ7uTIrzZewYH1ZOPzApz4ox0KWURKdHnmfM1v9kBTo10gKoT0KcIa5TCtZkLDuETr75Jh59uGg75aGskH/xt3jY7+kUQIzEq7700tigYWng09AogyAKzunvfyJxSp0DjBiCfnJl3Yn3WBpKmhqfIyb+tI3CREv/OCOytoX/y8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b=SLROPAAq; arc=none smtp.client-ip=217.140.110.172 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) header.d=arm.com header.i=@arm.com header.b="SLROPAAq" 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 1565249C7; Tue, 31 Mar 2026 07:13:57 -0700 (PDT) Received: from devkitleo.cambridge.arm.com (devkitleo.cambridge.arm.com [10.1.196.90]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id BC9EF3F641; Tue, 31 Mar 2026 07:13:59 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1774966442; bh=0WokdVZGVQOySMRtOFuViCjuFlNJiqco1s6MePa8OP0=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=SLROPAAq4tm06CZlvLbnK6UlSl74cbeF4PnQYHt9YVrFbK4s7f7jkSNb87VbkRboy XXkf4Lg/itNksvkyv6pSBDL/ICC5mCXYYcQ0SnbvaUsn7q3qpwFoRaJP/O5WcrtsmP 3Bp268ytYRpb6dxbptQOk8QvUD84hzofzk3QHT0g= From: Leonardo Bras To: Tian Zheng Cc: Leonardo Bras , maz@kernel.org, oupton@kernel.org, catalin.marinas@arm.com, corbet@lwn.net, pbonzini@redhat.com, will@kernel.org, yuzenghui@huawei.com, wangzhou1@hisilicon.com, liuyonglong@huawei.com, Jonathan.Cameron@huawei.com, yezhenyu2@huawei.com, linuxarm@huawei.com, joey.gouly@arm.com, kvmarm@lists.linux.dev, kvm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, skhan@linuxfoundation.org, suzuki.poulose@arm.com Subject: Re: [PATCH v3 0/5] Support the FEAT_HDBSS introduced in Armv9.5 Date: Tue, 31 Mar 2026 15:13:50 +0100 Message-ID: X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260225040421.2683931-1-zhengtian10@huawei.com> References: <20260225040421.2683931-1-zhengtian10@huawei.com> Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: 8bit On Wed, Feb 25, 2026 at 12:04:16PM +0800, Tian Zheng wrote: > This series of patches add support to the Hardware Dirty state tracking > Structure(HDBSS) feature, which is introduced by the ARM architecture > in the DDI0601(ID121123) version. > > The HDBSS feature is an extension to the architecture that enhances > tracking translation table descriptors' dirty state, identified as > FEAT_HDBSS. This feature utilizes hardware assistance to achieve dirty > page tracking, aiming to significantly reduce the overhead of scanning > for dirty pages. > > The purpose of this feature is to make the execution overhead of live > migration lower to both the guest and the host, compared to existing > approaches (write-protect or search stage 2 tables). > > After these patches, users(such as qemu) can use the > KVM_CAP_ARM_HW_DIRTY_STATE_TRACK ioctl to enable or disable the HDBSS > feature before and after the live migration. > > v2: > https://lore.kernel.org/linux-arm-kernel/20251121092342.3393318-1-zhengtian10@huawei.com/ > > v2->v3 changes: > - Remove the ARM64_HDBSS configuration option and ensure this feature > is only enabled in VHE mode. > - Move HDBSS-related variables to the arch-independent portion of the > kvm structure. > - Remove error messages during HDBSS enable/disable operations > - Change HDBSS buffer flushing from handle_exit to vcpu_put, > check_vcpu_requests, and kvm_handle_guest_abort. > - Add fault handling for HDBSS including buffer full, external abort, > and general protection fault (GPF). > - Add support for a 4KB HDBSS buffer size, mapped to the value 0b0000. > - Add a second argument to the ioctl to turn HDBSS on or off. > > Tian Zheng (1): > KVM: arm64: Document HDBSS ioctl > > eillon (4): > arm64/sysreg: Add HDBSS related register information > KVM: arm64: Add support to set the DBM attr during memory abort > KVM: arm64: Add support for FEAT_HDBSS > KVM: arm64: Enable HDBSS support and handle HDBSSF events > > Documentation/virt/kvm/api.rst | 16 +++++ > arch/arm64/include/asm/cpufeature.h | 5 ++ > arch/arm64/include/asm/esr.h | 7 ++ > arch/arm64/include/asm/kvm_host.h | 17 +++++ > arch/arm64/include/asm/kvm_mmu.h | 1 + > arch/arm64/include/asm/kvm_pgtable.h | 4 ++ > arch/arm64/include/asm/sysreg.h | 11 +++ > arch/arm64/kernel/cpufeature.c | 12 ++++ > arch/arm64/kvm/arm.c | 102 +++++++++++++++++++++++++++ > arch/arm64/kvm/hyp/pgtable.c | 6 ++ > arch/arm64/kvm/hyp/vhe/switch.c | 19 +++++ > arch/arm64/kvm/mmu.c | 70 ++++++++++++++++++ > arch/arm64/kvm/reset.c | 3 + > arch/arm64/tools/cpucaps | 1 + > arch/arm64/tools/sysreg | 29 ++++++++ > include/uapi/linux/kvm.h | 1 + > tools/include/uapi/linux/kvm.h | 1 + > 17 files changed, 305 insertions(+) > > -- > 2.33.0 > Hi Tian, I was thinking: maybe instead of putting the HDBSS (and HACDBS) stuff across a bunch of KVM files, we should try to focus them all on a single arch/arm64/kvm/dirty_bit.c file (plus a header such as arch/arm64/include/asm/kvm_dirty_bit.h). What is your opinion on that? Thanks! Leo