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X-CSE-ConnectionGUID: clw+0eCgReSO59sbrbSQKA== X-CSE-MsgGUID: mBixnfmyTBya4IZ3yd1rdw== X-IronPort-AV: E=McAfee;i="6800,10657,11534"; a="58178242" X-IronPort-AV: E=Sophos;i="6.18,214,1751266800"; d="scan'208";a="58178242" Received: from fmviesa007.fm.intel.com ([10.60.135.147]) by orvoesa112.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 26 Aug 2025 09:21:19 -0700 X-CSE-ConnectionGUID: 4bftntHvSDyXCbXfWoeHBA== X-CSE-MsgGUID: yT5mFORuQI+yXnTw64zxNA== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.18,214,1751266800"; d="scan'208";a="169126347" Received: from ldmartin-desk2.corp.intel.com (HELO [10.125.109.16]) ([10.125.109.16]) by fmviesa007-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 26 Aug 2025 09:21:18 -0700 Message-ID: <242057e5-10c0-4cf5-86d8-ace0f19e5760@intel.com> Date: Tue, 26 Aug 2025 09:21:17 -0700 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 v3 1/1] iommu/sva: Invalidate KVA range on kernel TLB flush To: Baolu Lu , "Tian, Kevin" , Jason Gunthorpe Cc: Joerg Roedel , Will Deacon , Robin Murphy , Jann Horn , Vasant Hegde , Alistair Popple , Peter Zijlstra , Uladzislau Rezki , Jean-Philippe Brucker , Andy Lutomirski , "Lai, Yi1" , "iommu@lists.linux.dev" , "security@kernel.org" , "linux-kernel@vger.kernel.org" References: <20250806052505.3113108-1-baolu.lu@linux.intel.com> <20250806155223.GV184255@nvidia.com> <20250806160904.GX184255@nvidia.com> <62d21545-9e75-41e3-89a3-f21dda15bf16@intel.com> <4a8df0e8-bd5a-44e4-acce-46ba75594846@linux.intel.com> <20250807195154.GO184255@nvidia.com> <87bfc80e-258e-4193-a56c-3096608aec30@linux.intel.com> <9a649ff4-55fe-478a-bfd7-f3287534499a@intel.com> From: Dave Hansen Content-Language: en-US Autocrypt: addr=dave.hansen@intel.com; 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charset=UTF-8 Content-Transfer-Encoding: 7bit On 8/25/25 19:49, Baolu Lu wrote: > What's strange is that order is almost always 0, except in the path of > remove_pmd_table() -> free_hugepage_table(), where order can be greater > than 0. However, in this context path, free_hugepage_table() isn't used > to free a page table page itself. Instead, it's used to free the actual > pages that a leaf PMD is pointing to. When I first read this, I thought you meant that remove_pmd_table() was trying to free a high-order page composed of multiple pte pages. I don't think it is doing that. Just to be clear: remove_pmd_table() has two modes: 1. The pmd_leaf() code that calls free_hugepage_table(). It is removing the memory pointed to by a PMD *entry*. It is *NOT* removing page tables themselves. 2. The !pmd_leaf() code that does remove the pointers to individual pte pages and frees them via free_pte_table(). *Neither* of these is freeing high-order page tables pages. It either frees plain old kernel data pages or it frees an order-0 page table page. In other words, the pmd_leaf() (mode #1) code is irrelevant to us. Those entries are all _PAGE_KERNEL so IOMMU accesses with user privilege can't do anything with them. Or have I just horribly confused myself?