From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 176EE23D7E6; Sat, 22 Nov 2025 16:23:41 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1763828622; cv=none; b=OOtj3jmFTQsCs2Yll+lRkhB1soq49+p4A0bsSwrxP/4kgzZaeUVLwNIgT6X7A+9IbwQtuEMzJE84HlcG6hAFII0JeixBrLnH6uHVPHpBcRRb+95o1tZnQSO+b/RTnVDXptR+GXcbW66DOqCIrkOLhI8+b+uH3Dn3U0NWvc3KKJU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1763828622; c=relaxed/simple; bh=KMqqBwj44p4qphVJeUmSKSm0+fweFHnjC7BLOlRrR24=; h=Date:Message-ID:From:To:Cc:Subject:In-Reply-To:References: MIME-Version:Content-Type; b=XJaTcJ57UlWliaucSn4jCSZcBTSmJDHWQ31NtzYTthrAhTyjB7DEZvW4NXNc3hUyS4taRmBMkXQZH2Nl/ipHCO4WRv8FrEWsFV/D8hADFAiXY9RDAFnY68XF60ZWf/87hsulIaDCCF+ZiPHswXS56GgPevvDeWlWnuYeJ4T1OEg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=mMlpZKx8; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="mMlpZKx8" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 96C25C113D0; Sat, 22 Nov 2025 16:23:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1763828621; bh=KMqqBwj44p4qphVJeUmSKSm0+fweFHnjC7BLOlRrR24=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=mMlpZKx8zmKMBNInoh6V2NVjfulX4oK1hI7skmvA6TOELnGW85vTcdTsxHj//sv1/ B9qCzKTzjP9oMGV0O8tR9u3ERVXloUcMPn/wLJAC/ChOxfKHKj3IMB2p3vtchPIYwE Bqd4MB/TuRSrc9hjCw9lCYRl3/BWJNsjfqbLRmGqO0yCT52sZX2qLuebB/lAVe+0g1 Rb5kNzj7z7lYpB2LWxbB4pxozpNnHNC+0cJNhMjw3v5jR1Sv3gPz75UC8OmwFPngk7 pz4gme5hMZ0VFgsQhKHSiK7GT/3IoEBZw8kMuBREK7GK1JwcDVYWEuaN6Oh4/UdbD5 93vPPP13VtrgA== Received: from sofa.misterjones.org ([185.219.108.64] helo=lobster-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 1vMqOh-00000007W12-19Ed; Sat, 22 Nov 2025 16:23:39 +0000 Date: Sat, 22 Nov 2025 16:23:38 +0000 Message-ID: <87jyzif33p.wl-maz@kernel.org> From: Marc Zyngier To: z00939249 Cc: , , , , , , , , , , , , , , , , Subject: Re: [PATCH v2 0/5] Support the FEAT_HDBSS introduced in Armv9.5 In-Reply-To: <90180222-5399-442c-b7a3-e65b7d0e1378@huawei.com> References: <20251121092342.3393318-1-zhengtian10@huawei.com> <86zf8fr9r2.wl-maz@kernel.org> <90180222-5399-442c-b7a3-e65b7d0e1378@huawei.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-doc@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: zhengtian10@huawei.com, oliver.upton@linux.dev, catalin.marinas@arm.com, corbet@lwn.net, pbonzini@redhat.com, will@kernel.org, linux-kernel@vger.kernel.org, yuzenghui@huawei.com, wangzhou1@hisilicon.com, yezhenyu2@huawei.com, xiexiangyou@huawei.com, zhengchuan@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, suzuki.poulose@arm.com X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false On Fri, 21 Nov 2025 10:21:16 +0000, z00939249 wrote: > > On 2025/11/21 17:54, Marc Zyngier wrote: > > On Fri, 21 Nov 2025 09:23:37 +0000, > > 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. The goal of this feature is to reduce the cost of surveying > >> for dirtied granules, with minimal effect on recording when a granule > >> has been dirtied. > >> > >> 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. > >> > >> This feature is similar to Intel's Page Modification Logging (PML), > >> offering hardware-assisted dirty tracking to reduce live migration > >> overhead. With PML support expanding beyond Intel, HDBSS introduces a > >> comparable mechanism for ARM. > > > > Where is the change log describing what was changed compared to the > > previous version? > > > > We gave you extensive comments back in March. You never replied to the > > feedback. And you now dump a whole set of patches, 6 months later, > > without the slightest indication of what has changed? > > > > Why should we make the effort to review this again? > > Apologies for the lack of proper changelog and the delayed follow-up > on the feedback provided in March. This was an oversight on our part > during the transition of maintainership for the HDBSS patch series. We > sincerely appreciate the thorough comments you shared earlier and > regret not responding in a timely manner. > > Below is a summary of the changes made from v1 to v2. > > v1: > https://lore.kernel.org/kvm/20250311040321.1460-1-yezhenyu2@huawei.com/ > > v1->v2 changes: > - Removed redundant macro definitions and switched to tool-generated. > - Split HDBSS interface and implementation into separate patches. > - Integrate system_supports_hdbss() into ARM feature initialization. > - Refactored HDBSS data structure to store meaningful values instead > of raw register contents. > - Fixed permission checks when applying DBM bits in page tables to > prevent potential memory corruption. > - Removed unnecessary dsb instructions. > - Drop the debugging printks. > - Merged the two patches "using ioctl to enable/disable the HDBSS > feature" and "support to handle the HDBSSF event" into one. Thanks for the update. Please make sure you always include such description in future version of this series. I hope the next version won't take as long (over 8 months between versions is counter productive). M. -- Jazz isn't dead. It just smells funny.