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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id C5E39C83F1F for ; Wed, 30 Aug 2023 18:54:17 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S245310AbjH3SxM (ORCPT ); Wed, 30 Aug 2023 14:53:12 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:38190 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S245586AbjH3Ph3 (ORCPT ); Wed, 30 Aug 2023 11:37:29 -0400 Received: from frasgout.his.huawei.com (frasgout.his.huawei.com [185.176.79.56]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9BAD5113 for ; Wed, 30 Aug 2023 08:37:24 -0700 (PDT) Received: from lhrpeml500005.china.huawei.com (unknown [172.18.147.200]) by frasgout.his.huawei.com (SkyGuard) with ESMTP id 4RbT0f1VYxz6HJZZ; Wed, 30 Aug 2023 23:36:18 +0800 (CST) Received: from localhost (10.202.227.76) by lhrpeml500005.china.huawei.com (7.191.163.240) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2507.31; Wed, 30 Aug 2023 16:37:21 +0100 Date: Wed, 30 Aug 2023 16:37:20 +0100 From: Jonathan Cameron To: =?ISO-8859-1?Q?J=F8rgen?= Hansen CC: Fan Ni , "qemu-devel@nongnu.org" , "linux-cxl@vger.kernel.org" , "gregory.price@memverge.com" , "hchkuo@avery-design.com.tw" , "cbrowy@avery-design.com" , "ira.weiny@intel.com" , "dan.j.williams@intel.com" , Adam Manzanares , "dave@stgolabs.net" , "nmtadam.samsung@gmail.com" , "nifan@outlook.com" Subject: Re: [Qemu PATCH v2 9/9] hw/mem/cxl_type3: Add dpa range validation for accesses to dc regions Message-ID: <20230830163720.00000f9c@Huawei.com> In-Reply-To: References: <20230725183939.2741025-1-fan.ni@samsung.com> <20230725183939.2741025-10-fan.ni@samsung.com> Organization: Huawei Technologies Research and Development (UK) Ltd. X-Mailer: Claws Mail 4.1.0 (GTK 3.24.33; x86_64-w64-mingw32) MIME-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.202.227.76] X-ClientProxiedBy: lhrpeml100006.china.huawei.com (7.191.160.224) To lhrpeml500005.china.huawei.com (7.191.163.240) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-cxl@vger.kernel.org > > + > > +/* > > + * This function check whether a dpa range [dpa, dpa + len) has been backed > > + * with dc extents, used when validating read/write to dc regions > > + */ > > +static bool test_region_block_backed(CXLType3Dev *ct3d, uint64_t dpa, > > + uint64_t len) > > +{ > > + int i; > > + CXLDCD_Region *region = &ct3d->dc.regions[0]; > > + uint64_t nbits; > > + long nr; > > + > > + if (dpa < region->base > > + || dpa >= region->base + ct3d->dc.total_capacity) > > + return false; > > + > > + /* > > + * spec 3.0 9.13.3: Regions are used in increasing-DPA order, with > > + * Region 0 being used for the lowest DPA of Dynamic Capacity and > > + * Region 7 for the highest DPA. > > + * So we check from the last region to find where the dpa belongs. > > + * access across multiple regions is not allowed. > > + */ > > + for (i = ct3d->dc.num_regions - 1; i >= 0; i--) { > > + region = &ct3d->dc.regions[i]; > > + if (dpa >= region->base) { > > + break; > > + } > > + } > > + > > + nr = (dpa - region->base) / region->block_size; > > > + nbits = len / region->block_size; oops. Len is probably always smaller than block_size (typically 8 or less) so nbits always 0. Should be 1 in those cases. > > + return find_next_zero_bit(region->blk_bitmap, nbits, nr) >= nr + nbits; > > The 2nd parameter to find_next_zero_bit is the length of the bitmap, so > shouldn't this be something like (also considering that len is the > read/write len, and will be smaller than the region block size): > > nbits = DIV_ROUND_UP(len, region->block_size); > > > return find_next_zero_bit(region->blk_bitmap, nbits + nr, nr) == > nbits + nr; Agreed with your suggestion. I'll carry that in my forward port of this series for now and update my tree at gitlab.com/jic23/qemu branch will probably be cxl-2023-08-30 a bit later today. Jonathan