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 mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 802C5C433EF for ; Thu, 11 Nov 2021 09:53:08 +0000 (UTC) Received: from smtp3.osuosl.org (smtp3.osuosl.org [140.211.166.136]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 1B2C361207 for ; Thu, 11 Nov 2021 09:53:08 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 1B2C361207 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=intel.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=lists.linux-foundation.org Received: from localhost (localhost [127.0.0.1]) by smtp3.osuosl.org (Postfix) with ESMTP id D905160B1C; Thu, 11 Nov 2021 09:53:07 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from smtp3.osuosl.org ([127.0.0.1]) by localhost (smtp3.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id GrpoH2AyI3wN; Thu, 11 Nov 2021 09:53:07 +0000 (UTC) Received: from lists.linuxfoundation.org (lf-lists.osuosl.org [140.211.9.56]) by smtp3.osuosl.org (Postfix) with ESMTPS id B7E1B60B20; Thu, 11 Nov 2021 09:53:06 +0000 (UTC) Received: from lf-lists.osuosl.org (localhost [127.0.0.1]) by lists.linuxfoundation.org (Postfix) with ESMTP id 9E19AC0035; Thu, 11 Nov 2021 09:53:06 +0000 (UTC) Received: from smtp2.osuosl.org (smtp2.osuosl.org [140.211.166.133]) by lists.linuxfoundation.org (Postfix) with ESMTP id 71321C001E for ; Thu, 11 Nov 2021 09:53:05 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by smtp2.osuosl.org (Postfix) with ESMTP id 4948840459 for ; Thu, 11 Nov 2021 09:53:05 +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 mlp5QXq0ZYQd for ; Thu, 11 Nov 2021 09:53:03 +0000 (UTC) X-Greylist: domain auto-whitelisted by SQLgrey-1.8.0 Received: from mga03.intel.com (mga03.intel.com [134.134.136.65]) by smtp2.osuosl.org (Postfix) with ESMTPS id 14F004015F for ; Thu, 11 Nov 2021 09:53:02 +0000 (UTC) X-IronPort-AV: E=McAfee;i="6200,9189,10164"; a="232826937" X-IronPort-AV: E=Sophos;i="5.87,225,1631602800"; d="scan'208";a="232826937" Received: from fmsmga006.fm.intel.com ([10.253.24.20]) by orsmga103.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 11 Nov 2021 01:53:02 -0800 X-IronPort-AV: E=Sophos;i="5.87,225,1631602800"; d="scan'208";a="733137980" Received: from silpixa00400314.ir.intel.com (HELO silpixa00400314) ([10.237.222.51]) by fmsmga006-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 11 Nov 2021 01:53:00 -0800 Date: Thu, 11 Nov 2021 09:52:53 +0000 From: Giovanni Cabiddu To: Alex Williamson Subject: Re: [PATCH] iommu/vt-d: Fix unmap_pages support Message-ID: References: <163659074748.1617923.12716161410774184024.stgit@omen> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <163659074748.1617923.12716161410774184024.stgit@omen> Organization: Intel Research and Development Ireland Ltd - Co. Reg. #308263 - Collinstown Industrial Park, Leixlip, County Kildare - Ireland Cc: iommu@lists.linux-foundation.org, dwmw2@infradead.org 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-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: iommu-bounces@lists.linux-foundation.org Sender: "iommu" I was able to hit the issue that this patch is fixing using the memory allocator in QATlib (https://github.com/intel/qatlib/) which uses vfio to map and unmap memory. This patch fixes the problem. On Wed, Nov 10, 2021 at 05:32:50PM -0700, Alex Williamson wrote: > 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 > Link: https://lore.kernel.org/all/20211002124012.18186-1-ajaygargnsit@gmail.com/ > Signed-off-by: Alex Williamson Tested-by: Giovanni Cabiddu _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu