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 X-Spam-Level: X-Spam-Status: No, score=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id D3990C43613 for ; Thu, 20 Jun 2019 04:16:21 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (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 A6178208CB for ; Thu, 20 Jun 2019 04:16:21 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org A6178208CB Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:43510 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.86_2) (envelope-from ) id 1hdoUl-0004q0-Oe for qemu-devel@archiver.kernel.org; Thu, 20 Jun 2019 00:16:19 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:42896) by lists.gnu.org with esmtp (Exim 4.86_2) (envelope-from ) id 1hdoTi-0003Lj-0A for qemu-devel@nongnu.org; Thu, 20 Jun 2019 00:15:15 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1hdoHd-0005JC-Dg for qemu-devel@nongnu.org; Thu, 20 Jun 2019 00:02:46 -0400 Received: from mx1.redhat.com ([209.132.183.28]:54094) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1hdoHd-0005IJ-6x for qemu-devel@nongnu.org; Thu, 20 Jun 2019 00:02:45 -0400 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 4F28230860B9; Thu, 20 Jun 2019 04:02:42 +0000 (UTC) Received: from xz-x1 (ovpn-12-78.pek2.redhat.com [10.72.12.78]) by smtp.corp.redhat.com (Postfix) with ESMTPS id DE5555D719; Thu, 20 Jun 2019 04:02:33 +0000 (UTC) Date: Thu, 20 Jun 2019 12:02:30 +0800 From: Peter Xu To: Auger Eric Message-ID: <20190620040230.GB9073@xz-x1> References: <1560934185-14152-1-git-send-email-yan.y.zhao@intel.com> <39c4c32b-e34a-8d8f-abbc-ab346ec5bed7@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <39c4c32b-e34a-8d8f-abbc-ab346ec5bed7@redhat.com> User-Agent: Mutt/1.11.4 (2019-03-13) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.44]); Thu, 20 Jun 2019 04:02:42 +0000 (UTC) X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 209.132.183.28 Subject: Re: [Qemu-devel] [PATCH] memory: do not do out of bound notification X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: pbonzini@redhat.com, Yan Zhao , qemu-devel@nongnu.org Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Wed, Jun 19, 2019 at 03:17:41PM +0200, Auger Eric wrote: > Hi Yan, > > [+ Peter] > > On 6/19/19 10:49 AM, Yan Zhao wrote: > > even if an entry overlaps with notifier's range, should not map/unmap > > out of bound part in the entry. > > I don't think the patch was based on the master as the trace at the very > end if not part of the upstream code. > > > > This would cause problem in below case: > > 1. initially there are two notifiers with ranges > > 0-0xfedfffff, 0xfef00000-0xffffffffffffffff, > > IOVAs from 0x3c000000 - 0x3c1fffff is in shadow page table. > > > > 2. in vfio, memory_region_register_iommu_notifier() is followed by > > memory_region_iommu_replay(), which will first call address space unmap, > > and walk and add back all entries in vtd shadow page table. e.g. > > (1) for notifier 0-0xfedfffff, > > IOVAs from 0 - 0xffffffff get unmapped, > > and IOVAs from 0x3c000000 - 0x3c1fffff get mapped > > While the patch looks sensible, the issue is the notifier scope used in > vtd_address_space_unmap is not a valid mask (ctpop64(size) != 1). Then > the size is recomputed (either using n = 64 - clz64(size) for the 1st > notifier or n = s->aw_bits for the 2d) and also the entry (especially > for the 2d notifier where it becomes 0) to get a proper alignment. > > vtd_page_walk sends notifications per block or page (with valid > addr_mask) so stays within the notifier. > > Modifying the entry->iova/addr_mask again in memory_region_notify_one > leads to unaligned start address / addr_mask. I don't think we want that. > > Can't we modity the vtd_address_space_unmap() implementation to split > the invalidation in smaller chunks instead? Seems workable, to be explicit - we can even cut it into chunks with different size to be efficient. Like, this range: 0x0e00_0000 - 0x1_0000_0000 (size 0xf200_0000) can be one of this: 0x0e000000 - 0x1000_0000 (size 0x0200_0000) plus one of this: 0x1000_0000 - 0x1_0000_0000 (size 0xf000_0000) Yan, could you help explain the issue better on how to reproduce and what's the error when the problem occurs? For example, is that happened when a device hot-plugged into an existing VFIO container (with some mapped IOVAs)? Did you get host DMA errors later on? Thanks, -- Peter Xu