From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from smtp2.osuosl.org (smtp2.osuosl.org [140.211.166.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id BFDC0C433EF for ; Fri, 26 Nov 2021 12:47:30 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by smtp2.osuosl.org (Postfix) with ESMTP id 4AE824014A; Fri, 26 Nov 2021 12:47:30 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from smtp2.osuosl.org ([127.0.0.1]) by localhost (smtp2.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id UPZq5_ARc54U; Fri, 26 Nov 2021 12:47:29 +0000 (UTC) Received: from lists.linuxfoundation.org (lf-lists.osuosl.org [140.211.9.56]) by smtp2.osuosl.org (Postfix) with ESMTPS id E163340102; Fri, 26 Nov 2021 12:47:28 +0000 (UTC) Received: from lf-lists.osuosl.org (localhost [127.0.0.1]) by lists.linuxfoundation.org (Postfix) with ESMTP id B06FCC001E; Fri, 26 Nov 2021 12:47:28 +0000 (UTC) Received: from smtp1.osuosl.org (smtp1.osuosl.org [140.211.166.138]) by lists.linuxfoundation.org (Postfix) with ESMTP id 331D1C0012 for ; Fri, 26 Nov 2021 12:47:27 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by smtp1.osuosl.org (Postfix) with ESMTP id 13699826D5 for ; Fri, 26 Nov 2021 12:47:27 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from smtp1.osuosl.org ([127.0.0.1]) by localhost (smtp1.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id NpXWpQ89_DXd for ; Fri, 26 Nov 2021 12:47:26 +0000 (UTC) X-Greylist: domain auto-whitelisted by SQLgrey-1.8.0 Received: from mga07.intel.com (mga07.intel.com [134.134.136.100]) by smtp1.osuosl.org (Postfix) with ESMTPS id 352898267F for ; Fri, 26 Nov 2021 12:47:26 +0000 (UTC) X-IronPort-AV: E=McAfee;i="6200,9189,10179"; a="299062970" X-IronPort-AV: E=Sophos;i="5.87,265,1631602800"; d="scan'208";a="299062970" Received: from orsmga008.jf.intel.com ([10.7.209.65]) by orsmga105.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 26 Nov 2021 04:47:25 -0800 X-IronPort-AV: E=Sophos;i="5.87,266,1631602800"; d="scan'208";a="510631193" Received: from blu2-mobl3.ccr.corp.intel.com (HELO [10.254.210.4]) ([10.254.210.4]) by orsmga008-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 26 Nov 2021 04:47:08 -0800 Message-ID: <79b1fe69-9672-6cb7-88b1-f4eaffa7add9@linux.intel.com> Date: Fri, 26 Nov 2021 20:47:05 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:91.0) Gecko/20100101 Thunderbird/91.3.2 Subject: Re: [PATCH 2/2] iommu/vt-d: Fix unmap_pages support Content-Language: en-US To: Joerg Roedel References: <20211122032458.2549761-1-baolu.lu@linux.intel.com> <20211122032458.2549761-3-baolu.lu@linux.intel.com> From: Lu Baolu In-Reply-To: <20211122032458.2549761-3-baolu.lu@linux.intel.com> Cc: iommu@lists.linux-foundation.org, Alex Williamson , Christophe JAILLET X-BeenThere: iommu@lists.linux-foundation.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: Development issues for Linux IOMMU support List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Errors-To: iommu-bounces@lists.linux-foundation.org Sender: "iommu" On 2021/11/22 11:24, Lu Baolu wrote: > From: Alex Williamson > > When supporting only the .map and .unmap callbacks of iommu_ops, > the IOMMU driver can make assumptions about the size and alignment > used for mappings based on the driver provided pgsize_bitmap. VT-d > previously used essentially PAGE_MASK for this bitmap as any power > of two mapping was acceptably filled by native page sizes. > > However, with the .map_pages and .unmap_pages interface we're now > getting page-size and count arguments. If we simply combine these > as (page-size * count) and make use of the previous map/unmap > functions internally, any size and alignment assumptions are very > different. > > As an example, a given vfio device assignment VM will often create > a 4MB mapping at IOVA pfn [0x3fe00 - 0x401ff]. On a system that > does not support IOMMU super pages, the unmap_pages interface will > ask to unmap 1024 4KB pages at the base IOVA. dma_pte_clear_level() > will recurse down to level 2 of the page table where the first half > of the pfn range exactly matches the entire pte level. We clear the > pte, increment the pfn by the level size, but (oops) the next pte is > on a new page, so we exit the loop an pop back up a level. When we > then update the pfn based on that higher level, we seem to assume > that the previous pfn value was at the start of the level. In this > case the level size is 256K pfns, which we add to the base pfn and > get a results of 0x7fe00, which is clearly greater than 0x401ff, > so we're done. Meanwhile we never cleared the ptes for the remainder > of the range. When the VM remaps this range, we're overwriting valid > ptes and the VT-d driver complains loudly, as reported by the user > report linked below. > > The fix for this seems relatively simple, if each iteration of the > loop in dma_pte_clear_level() is assumed to clear to the end of the > level pte page, then our next pfn should be calculated from level_pfn > rather than our working pfn. > > Fixes: 3f34f1259776 ("iommu/vt-d: Implement map/unmap_pages() iommu_ops callback") > Reported-by: Ajay Garg > Signed-off-by: Alex Williamson > Tested-by: Giovanni Cabiddu > Link:https://lore.kernel.org/all/20211002124012.18186-1-ajaygargnsit@gmail.com/ > Link:https://lore.kernel.org/r/163659074748.1617923.12716161410774184024.stgit@omen > Signed-off-by: Lu Baolu 0-day build robot reported an error on this patch. "drivers/iommu/intel/iommu.c:1344:7: warning: variable 'level_pfn' is used uninitialized whenever 'if' condition is true [-Wsometimes-uninitialized] " I will send a v2 of this patch. Sorry for the inconvenience. Best regards baolu _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu