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=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no 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 CE3D5C83007 for ; Wed, 29 Apr 2020 08:47:43 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B4B6120775 for ; Wed, 29 Apr 2020 08:47:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726599AbgD2Irn (ORCPT ); Wed, 29 Apr 2020 04:47:43 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36012 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S1726345AbgD2Irm (ORCPT ); Wed, 29 Apr 2020 04:47:42 -0400 Received: from theia.8bytes.org (8bytes.org [IPv6:2a01:238:4383:600:38bc:a715:4b6d:a889]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 6D0C6C03C1AD for ; Wed, 29 Apr 2020 01:47:42 -0700 (PDT) Received: by theia.8bytes.org (Postfix, from userid 1000) id 6F3E329A; Wed, 29 Apr 2020 10:47:40 +0200 (CEST) Date: Wed, 29 Apr 2020 10:47:38 +0200 From: Joerg Roedel To: Qian Cai Cc: iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org Subject: Re: [RFC PATCH] iommu/amd: fix a race in fetch_pte() Message-ID: <20200429084738.GM21900@8bytes.org> References: <20200418121022.GA6113@8bytes.org> <57CBF6B2-4745-4E36-9AA5-7E0876E3DA8F@lca.pw> <20200418183429.GH21900@8bytes.org> <7D03A3E2-647B-4FAD-886D-EE2764EC1EDB@lca.pw> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <7D03A3E2-647B-4FAD-886D-EE2764EC1EDB@lca.pw> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Qian, On Mon, Apr 20, 2020 at 09:26:12AM -0400, Qian Cai wrote: > > No dice. There could be some other races. For example, Okay, I think I know what is happening. The increase_address_space() function increases the address space, but does not update the DTE and does not flush the old DTE from the caches. But this needs to happen before domain->pt_root is updated, because otherwise another CPU can come along and map something into the increased address-space which is not yet accessible by the device because the DTE is not updated yet. Regards, Joerg