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 509D5C636CC for ; Mon, 20 Feb 2023 11:46:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231844AbjBTLqy (ORCPT ); Mon, 20 Feb 2023 06:46:54 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39108 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231873AbjBTLqw (ORCPT ); Mon, 20 Feb 2023 06:46:52 -0500 Received: from frasgout.his.huawei.com (frasgout.his.huawei.com [185.176.79.56]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id AA8CA1B336 for ; Mon, 20 Feb 2023 03:46:49 -0800 (PST) Received: from lhrpeml500005.china.huawei.com (unknown [172.18.147.226]) by frasgout.his.huawei.com (SkyGuard) with ESMTP id 4PL0rb1t2Gz6J68P; Mon, 20 Feb 2023 19:42:07 +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 15.1.2507.17; Mon, 20 Feb 2023 11:46:47 +0000 Date: Mon, 20 Feb 2023 11:46:46 +0000 From: Jonathan Cameron To: Gregory Price CC: Jonathan Cameron via , Michael Tsirkin , Ben Widawsky , , , Ira Weiny , Gregory Price , Philippe =?ISO-8859-1?Q?Mathieu-Daud=E9?= , Mike Maslenkin Subject: Re: [PATCH 2/2] hw/cxl: Multi-Region CXL Type-3 Devices (Volatile and Persistent) Message-ID: <20230220114646.000000ff@Huawei.com> In-Reply-To: References: <20230131163847.23025-1-Jonathan.Cameron@huawei.com> <20230131163847.23025-3-Jonathan.Cameron@huawei.com> <20230217161617.000064d1@huawei.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: lhrpeml500002.china.huawei.com (7.191.160.78) 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 On Fri, 17 Feb 2023 06:08:57 -0500 Gregory Price wrote: > On Fri, Feb 17, 2023 at 04:16:17PM +0000, Jonathan Cameron via wrote: > > On Tue, 31 Jan 2023 16:38:47 +0000 > > Jonathan Cameron via wrote: > > > > > From: Gregory Price > > > > > > This commit enables each CXL Type-3 device to contain one volatile > > > memory region and one persistent region. > > > > > > Two new properties have been added to cxl-type3 device initialization: > > > [volatile-memdev] and [persistent-memdev] > > > > > > The existing [memdev] property has been deprecated and will default the > > > memory region to a persistent memory region (although a user may assign > > > the region to a ram or file backed region). It cannot be used in > > > combination with the new [persistent-memdev] property. > > > > > > Partitioning volatile memory from persistent memory is not yet supported. > > > > > > Volatile memory is mapped at DPA(0x0), while Persistent memory is mapped > > > at DPA(vmem->size), per CXL Spec 8.2.9.8.2.0 - Get Partition Info. > > > > > > Signed-off-by: Gregory Price > > > Signed-off-by: Jonathan Cameron > > > > > Hi Gregory, > > > > I've added support for multiple HDM decoders and hence can now > > test both volatile and non volatile on same device. > > It very nearly all works. With one exception which is I couldn't > > poke the first byte of the non volatile region. > > > > I think we have an off by one in a single check. > > > > Interestingly it makes no difference when creating an FS on top > > (which was my standard test) so I only noticed when poking memory > > addresses directly to sanity check the HDM decoder setup. > > > > I'll roll a v2 if no one shouts out that I'm wrong. > > > > Note that adding multiple HDM decoders massively increases > > the number of test cases over what we had before to poke all the > > corners so I may well be missing stuff. Hopefully can send an RFC > > of that support out next week. > > > > Jonathan > > > > Very cool! Thanks for pushing this over the finishing line. > > All my testing so far has been really smooth since getting the TCG issue > worked out. > > > > -MemTxResult cxl_type3_read(PCIDevice *d, hwaddr host_addr, uint64_t *data, > > > - unsigned size, MemTxAttrs attrs) > [...] > > > + if (vmr) { > > > + if (*dpa_offset <= int128_get64(vmr->size)) { > > > > Off by one I think. < > > > > Yes that makes sense, should be <. Derp derp. > > Though I think this may alludes to more off-by-one issues? This says > > if (dpa_offset < vmr->size) > > but dpa_offset should be (hpa - memory_region_base), > > The HPA is used by memory access routing for the whole system to determine > what device it should access. > > If that corner case is being hit, doesn't it imply the higher level code > is also susceptible to this, and is routing accesses to the wrong device? I don't think so though I may be missing something. Say vmr->size = 8 hpa dpa_offset 0 0 1 1 2 2 3 3 4 4 5 5 6 6 7 7 8 0 etc Also the writes are turning up where I expect them to. Also just noticed that the code is setting Memory_base in the CXL dvsec. Given we are emulating a device as if it has been freshly powered up those should not be set - it's the OS or firmware's job to set them up. Harmless though, so can be a cleanup to follow the main series. We don't currently handle dvsec range based routing anyway and I'm not sure we ever will as it is a pain to test without some firmware or OS code to program them for us. Note that if you update your kernel to cxl/next it will currently fail as the Range register emulation is (I think) rather over enthusiastic and currently decides to emulate the HDM decoders for the QEMU emulated type 3 devices. https://lore.kernel.org/linux-cxl/167640366272.935665.1056268838301725481.stgit@dwillia2-xfh.jf.intel.com/T/#m6c025d5c9b27d8360a64079593f6c5adaa408772 Jonathan > > ~Gregory