From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mgamail.intel.com (mgamail.intel.com [192.198.163.7]) (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 F17C61EDA1E for ; Sat, 11 Oct 2025 06:34:32 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=192.198.163.7 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1760164474; cv=none; b=jL9/fu04Da6mnBJ2q+6X24KEJkYM4qD5zubftlaJ+gdYoWsfl3YLs4TGkOQbfSXVZ1YEYNVX9rugoQXgmeGej34JFs2n+DkIXjY9HvUVIfsY9SX35nDkqCxbtzWLTGCLw2NXh4zqP/8H5PG1rF8au7vXLq6QmXV8u0iGh18hLp8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1760164474; c=relaxed/simple; bh=ZHoGBUbqzplr1SqOVtjjpzhNhjDVkJ8UthME/KpzTy8=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=eub0Nv6PRKQay5YJ2KdV1w5pg2EbBZK0ggiq3gAW+G6y0yPOIU4WGNHb5nFi3Wc5JjdvpZRLlqStS1YsY+Us5J97hnYEafdqkQNqeK/5/3Gnrt7ukIUVCBNpO9V5cdqBHCiNRhvVM4FFbA0yGiWt+tO8yH/fywGwFZMaTJnEqAI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.intel.com; spf=pass smtp.mailfrom=linux.intel.com; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b=GpuRKwpb; arc=none smtp.client-ip=192.198.163.7 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.intel.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.intel.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b="GpuRKwpb" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1760164473; x=1791700473; h=message-id:date:mime-version:subject:to:cc:references: from:in-reply-to:content-transfer-encoding; bh=ZHoGBUbqzplr1SqOVtjjpzhNhjDVkJ8UthME/KpzTy8=; b=GpuRKwpb5feBKRsoFo8CU4lzGAf7o8B9JPDmBlq9vLjFtgUypJexDd1M hP3B/qb2ceBE8JOjPmKX+MRPrJbQbbas848jPnsT+KmUmeMmLqu41d6sj 0P0BwT+l2KCIdLBGhxfS1rk3QjQJkONSDWjIKra7Vi+0fmswPvLySsD9t A/nTZm81q84KG0pjJun6n7uoGo22kLG+gM4smZ0BuZYsPaYgyqHDo15K9 pi8DbCMIghrTQ5+NrQHF1Jyaly3IGLw5BwIWu8EUj69jvCVYF+VBZMe9F PIzOTYfkqdQ6Q5LxHcR5GARz9shDOFFV6ok0j2ATeOHVV7hlFh4UFuvXA Q==; X-CSE-ConnectionGUID: uMn0P3IaTuK8oJaU6yARAw== X-CSE-MsgGUID: MmOWUrc5SiqepJR/vvvABA== X-IronPort-AV: E=McAfee;i="6800,10657,11578"; a="87838069" X-IronPort-AV: E=Sophos;i="6.19,220,1754982000"; d="scan'208";a="87838069" Received: from fmviesa002.fm.intel.com ([10.60.135.142]) by fmvoesa101.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 10 Oct 2025 23:34:32 -0700 X-CSE-ConnectionGUID: VcSPh3W0SuyKVz7g68oZuw== X-CSE-MsgGUID: hnXs8JcbTyOib7kc4CEhjA== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.19,220,1754982000"; d="scan'208";a="204824426" Received: from allen-sbox.sh.intel.com (HELO [10.239.159.30]) ([10.239.159.30]) by fmviesa002-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 10 Oct 2025 23:34:27 -0700 Message-ID: <7a001cb9-fb09-487c-bfa9-e2d329b0f6a8@linux.intel.com> Date: Sat, 11 Oct 2025 14:30:54 +0800 Precedence: bulk X-Mailing-List: iommu@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v5 6/8] mm: Introduce deferred freeing for kernel page tables To: David Hildenbrand , Joerg Roedel , Will Deacon , Robin Murphy , Kevin Tian , Jason Gunthorpe , Jann Horn , Vasant Hegde , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , Alistair Popple , Peter Zijlstra , Uladzislau Rezki , Jean-Philippe Brucker , Andy Lutomirski , Yi Lai Cc: iommu@lists.linux.dev, security@kernel.org, x86@kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Dave Hansen References: <20250919054007.472493-1-baolu.lu@linux.intel.com> <20250919054007.472493-7-baolu.lu@linux.intel.com> <5b494700-a3af-4feb-8c5f-1ca424ad9841@redhat.com> Content-Language: en-US From: Baolu Lu In-Reply-To: <5b494700-a3af-4feb-8c5f-1ca424ad9841@redhat.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 10/10/25 23:47, David Hildenbrand wrote: > On 19.09.25 07:40, Lu Baolu wrote: >> From: Dave Hansen >> >> This introduces a conditional asynchronous mechanism, enabled by >> CONFIG_ASYNC_PGTABLE_FREE. When enabled, this mechanism defers the >> freeing >> of pages that are used as page tables for kernel address mappings. These >> pages are now queued to a work struct instead of being freed immediately. >> > > Okay, I now looked at patch #8 and I think the whole reason of this > patch is "batch-free page tables to minimize the impact of an expensive > cross-page table operation" which is a single TLB flush. > >> This deferred freeing provides a safe context for a future patch to add > > So I would claridy here instead something like > > "This deferred freeing allows for batch-freeing of page tables, > providing a safe context for performing a single expensive operation > (TLB flush) for a batch of kernel page tables instead of performing that > expensive operation for each page table." The commit message has been updated, and CONFIG_ASYNC_PGTABLE_FREE has been replaced with CONFIG_ASYNC_KERNEL_PGTABLE_FREE. Thank you for the comments. Thanks, baolu