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 370FCC4332F for ; Tue, 1 Nov 2022 16:14:17 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229738AbiKAQOQ (ORCPT ); Tue, 1 Nov 2022 12:14:16 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52814 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230201AbiKAQOP (ORCPT ); Tue, 1 Nov 2022 12:14:15 -0400 Received: from frasgout.his.huawei.com (frasgout.his.huawei.com [185.176.79.56]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 4C49B1C435 for ; Tue, 1 Nov 2022 09:14:12 -0700 (PDT) Received: from fraeml708-chm.china.huawei.com (unknown [172.18.147.206]) by frasgout.his.huawei.com (SkyGuard) with ESMTP id 4N1w5l3q0qz689w9; Wed, 2 Nov 2022 00:12:27 +0800 (CST) Received: from lhrpeml500005.china.huawei.com (7.191.163.240) by fraeml708-chm.china.huawei.com (10.206.15.36) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.31; Tue, 1 Nov 2022 17:14:09 +0100 Received: from localhost (10.122.247.231) 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 15.1.2375.31; Tue, 1 Nov 2022 16:14:08 +0000 Date: Tue, 1 Nov 2022 16:14:07 +0000 From: Jonathan Cameron To: Gregory Price CC: , , , , , Gregory Price Subject: Re: [PATCH] hw/i386/pc.c: CXL Fixed Memory Window should not reserve e820 in bios Message-ID: <20221101161407.00007366@huawei.com> In-Reply-To: <20221026205912.8579-1-gregory.price@memverge.com> References: <20221026205912.8579-1-gregory.price@memverge.com> Organization: Huawei Technologies R&D (UK) Ltd. X-Mailer: Claws Mail 4.0.0 (GTK+ 3.24.29; x86_64-w64-mingw32) MIME-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.122.247.231] X-ClientProxiedBy: lhrpeml500001.china.huawei.com (7.191.163.213) 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 Wed, 26 Oct 2022 16:59:13 -0400 Gregory Price wrote: > Early-boot e820 records will be inserted by the bios/efi/early boot > software and be reported to the kernel via insert_resource. Later, when > CXL drivers iterate through the regions again, they will insert another > resource and make the RESERVED memory area a child. > > This RESERVED memory area causes the memory region to become unusable, > and as a result attempting to create memory regions with > > `cxl create-region ...` > > Will fail due to the RESERVED area intersecting with the CXL window. > > During boot the following traceback is observed: > > 0xffffffff81101650 in insert_resource_expand_to_fit () > 0xffffffff83d964c5 in e820__reserve_resources_late () > 0xffffffff83e03210 in pcibios_resource_survey () > 0xffffffff83e04f4a in pcibios_init () > > Which produces a call to reserve the CFMWS area: > > (gdb) p *new > $54 = {start = 0x290000000, end = 0x2cfffffff, name = "Reserved", > flags = 0x200, desc = 0x7, parent = 0x0, sibling = 0x0, > child = 0x0} > > Later the Kernel parses ACPI tables and reserves the exact same area as > the CXL Fixed Memory Window: > > 0xffffffff811016a4 in insert_resource_conflict () > insert_resource () > 0xffffffff81a81389 in cxl_parse_cfmws () > 0xffffffff818c4a81 in call_handler () > acpi_parse_entries_array () > > (gdb) p/x *new > $59 = {start = 0x290000000, end = 0x2cfffffff, name = "CXL Window 0", > flags = 0x200, desc = 0x0, parent = 0x0, sibling = 0x0, > child = 0x0} > > This produces the following output in /proc/iomem: > > 590000000-68fffffff : CXL Window 0 > 590000000-68fffffff : Reserved > > This reserved area causes `get_free_mem_region()` to fail due to a check > against `__region_intersects()`. Due to this reserved area, the > intersect check will only ever return REGION_INTERSECTS, which causes > `cxl create-region` to always fail. > > Signed-off-by: Gregory Price My understanding of e820 is limited, but from discussions with Intel folk I believe this fix to be correct - we should never have had e820 regions for CXL Fixed Memory Windows. As such Acked-by: Jonathan Cameron > --- > hw/i386/pc.c | 2 -- > 1 file changed, 2 deletions(-) > > diff --git a/hw/i386/pc.c b/hw/i386/pc.c > index 768982ae9a..203c90fedb 100644 > --- a/hw/i386/pc.c > +++ b/hw/i386/pc.c > @@ -1062,7 +1062,6 @@ void pc_memory_init(PCMachineState *pcms, > hwaddr cxl_size = MiB; > > cxl_base = pc_get_cxl_range_start(pcms); > - e820_add_entry(cxl_base, cxl_size, E820_RESERVED); > memory_region_init(mr, OBJECT(machine), "cxl_host_reg", cxl_size); > memory_region_add_subregion(system_memory, cxl_base, mr); > cxl_resv_end = cxl_base + cxl_size; > @@ -1078,7 +1077,6 @@ void pc_memory_init(PCMachineState *pcms, > memory_region_init_io(&fw->mr, OBJECT(machine), &cfmws_ops, fw, > "cxl-fixed-memory-region", fw->size); > memory_region_add_subregion(system_memory, fw->base, &fw->mr); > - e820_add_entry(fw->base, fw->size, E820_RESERVED); > cxl_fmw_base += fw->size; > cxl_resv_end = cxl_fmw_base; > }