From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from szxga04-in.huawei.com (szxga04-in.huawei.com [45.249.212.190]) (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 E30CA32ED43 for ; Thu, 11 Sep 2025 14:08:59 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=45.249.212.190 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1757599742; cv=none; b=u30csR0x1c3pTXfboKy0QW4MEm2ITUIIS0CvaoUu1vtLyyvSIk+bqVKy541Zw1ct+G8aP/mt0Zv4KYJbOfih4shhkhGu4EPDJ3YCM3Pk1IuteHXUnuBOupnoSYmEwRxxq0I8KYTDf1JMKFZKGzRMP/nImC+n4APeJtVasgXk3fE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1757599742; c=relaxed/simple; bh=2pqgafZIU6dCGuLxRRcQ4J9D0AL2bMkEFuyleWWTbWA=; h=Message-ID:Date:MIME-Version:Subject:To:CC:References:From: In-Reply-To:Content-Type; b=eu0hBLpyeRFSRu0qRiOhaKgk4hSBoZkMYLsro6/L52ZiHVTkFbXHC0yAeQnspXBG32G+OBrpJ2Mke2vgeOhaeMDYXOur3GS6yoh1hjGpDpRDgCuieuUw+5JpSEHddoJ3ykuXX2TkB01d6fsW1BocDS2oQZZqfVCbpVxvqkz/JtI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=huawei.com; spf=pass smtp.mailfrom=huawei.com; arc=none smtp.client-ip=45.249.212.190 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=huawei.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=huawei.com Received: from mail.maildlp.com (unknown [172.19.88.234]) by szxga04-in.huawei.com (SkyGuard) with ESMTP id 4cMzq66vynz2VRgH; Thu, 11 Sep 2025 22:05:38 +0800 (CST) Received: from kwepemj200003.china.huawei.com (unknown [7.202.194.15]) by mail.maildlp.com (Postfix) with ESMTPS id 64F2F140296; Thu, 11 Sep 2025 22:08:56 +0800 (CST) Received: from [10.67.120.170] (10.67.120.170) by kwepemj200003.china.huawei.com (7.202.194.15) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1544.11; Thu, 11 Sep 2025 22:08:55 +0800 Message-ID: Date: Thu, 11 Sep 2025 22:08:55 +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 0/2] iommu: Add io_ptdump debug interface for iommu To: Jason Gunthorpe CC: , , , , , , , , , , , References: <20250814093005.2040511-1-xiaqinxin@huawei.com> <20250902161028.GC184112@ziepe.ca> <20250910141547.GD882933@ziepe.ca> From: Qinxin Xia In-Reply-To: <20250910141547.GD882933@ziepe.ca> Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 8bit X-ClientProxiedBy: kwepems500001.china.huawei.com (7.221.188.70) To kwepemj200003.china.huawei.com (7.202.194.15) On 2025/9/10 22:15:47, Jason Gunthorpe wrote: > On Wed, Sep 10, 2025 at 11:20:08AM +0800, Qinxin Xia wrote: >> Ok, I see, my colleague Wang Zhou also released a version of io_ptdump >> a long time ago, which is implemented in smmu debugfs. Will recommends that >> io_ptdump be implemented in a way similar to CPU page table dump. Using >> debugfs to expose the data and using format-specific callbacks to implement >> specific data dumps, I'll talk to him about this as well. > > I feel we should have a iommu subsystem debugfs and per-iommu_domain > directories to dump the page tables. > > The smmu debugfs can report what iommu_domains each STE/CD is > referencing. > > This also needs RCU freeing of page table levels as a locking > strategy. > > Jason > Thanks, I'll add RCU in the next version, but there's some confusion, Do you mean to create a directory for each domain? like： /sys/kernel/debug/io_page_tables/domain_xxxx (xxxx=domain addr) tree domain_xxxx like: domain_xxxx └── group x │ └── device └── io_ptdump And the current design is such: User Space Interface └── DebugFS file: /sys/kernel/debug/io_page_tables └── Operation: Reading this file triggers the entire debug information collection process Kernel Space Components ├── Configuration option (CONFIG_IO_PTDUMP_DEBUGFS) ├── Initialization module (mm/io_ptdump.c) │ └── device_initcall(io_ptdump_init) │ └── io_ptdump_debugfs_register("io_page_tables") ├── DebugFS backend (mm/io_ptdump_debugfs.c) │ └── DEFINE_SHOW_ATTRIBUTE(io_ptdump) │ └── .show = io_ptdump_show │ └── iommu_group_and_iova_dump(m) └── IOMMU core extension (drivers/iommu/iommu.c) └── iommu_group_and_iova_dump() ├── Traverse all IOMMU groups (via iommu_group_kset) ├── Filter groups with default domain using DMA_IOVA cookie ├── Build domain-group hierarchy │ ├── domain_list: list head │ ├── dump_domain: domain entry │ │ ├── domain: pointer to iommu_domain │ │ └── groups: list head of groups │ └── dump_group: group entry │ └── group: pointer to iommu_group ├── Output domain information ├── Output group and device information └── Call iommu_iova_info_dump() to output IOVA mappings └── Traverse IOVA red-black tree └── Call domain->ops->dump_iova_prot() to get protection information └── ARM SMMUv3 implementation (drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c) └── arm_smmu_dump_iova_prot() └── Call io_pgtable_ops->dump_iova_prot() └── ARM LPAE implementation (drivers/iommu/io-pgtable-arm.c) └── arm_lpae_dump_iova_prot() ├── Use __arm_lpae_iopte_walk() to traverse page tables ├── Obtain page table entry and level information ├── Format and output mapping range and information └── Call dump_prot() to output protection flags └── Use prot_bits array to parse permission bits Do you mean that the interface in io-pgtable-arm.c is directly invoked during the process of obtaining page table information without passing through arm-smmu-v3.c? I'll add STE and CD dumps to the next release. Any other suggestions?