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 2DE22C433EF for ; Thu, 28 Apr 2022 11:48:56 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1345717AbiD1LwI (ORCPT ); Thu, 28 Apr 2022 07:52:08 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42618 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1345691AbiD1LwH (ORCPT ); Thu, 28 Apr 2022 07:52:07 -0400 Received: from szxga01-in.huawei.com (szxga01-in.huawei.com [45.249.212.187]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id AB674689B5 for ; Thu, 28 Apr 2022 04:48:52 -0700 (PDT) Received: from dggpemm500020.china.huawei.com (unknown [172.30.72.56]) by szxga01-in.huawei.com (SkyGuard) with ESMTP id 4Kpv5c1xC1zhY1t; Thu, 28 Apr 2022 19:48:36 +0800 (CST) Received: from dggpemm500001.china.huawei.com (7.185.36.107) by dggpemm500020.china.huawei.com (7.185.36.49) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.24; Thu, 28 Apr 2022 19:48:50 +0800 Received: from [10.174.177.243] (10.174.177.243) by dggpemm500001.china.huawei.com (7.185.36.107) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.24; Thu, 28 Apr 2022 19:48:50 +0800 Message-ID: <46c0fff6-dff9-5669-7aa7-79bae0883a7e@huawei.com> Date: Thu, 28 Apr 2022 19:48:50 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:91.0) Gecko/20100101 Thunderbird/91.5.1 Subject: Re: [PATCH 0/4] arm64: Cleanup ioremap() and support ioremap_prot() Content-Language: en-US To: Will Deacon CC: Catalin Marinas , Andrew Morton , , , References: <20220427121413.168468-1-wangkefeng.wang@huawei.com> <20220428104612.GA14515@willie-the-truck> From: Kefeng Wang In-Reply-To: <20220428104612.GA14515@willie-the-truck> Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 8bit X-Originating-IP: [10.174.177.243] X-ClientProxiedBy: dggems702-chm.china.huawei.com (10.3.19.179) To dggpemm500001.china.huawei.com (7.185.36.107) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2022/4/28 18:46, Will Deacon wrote: > On Wed, Apr 27, 2022 at 08:14:09PM +0800, Kefeng Wang wrote: >> Let's arm64 use GENERIC_IOREMAP to cleanup code, and >> support ioremap_prot()/HAVE_IOREMAP_PROT, which could >> enable generic_access_phys(). >> >> Kefeng Wang (4): >> mm: ioremap: Setup phys_addr of struct vm_struct >> mm: ioremap: Add arch_ioremap/iounmap_check() >> arm64: mm: Convert to GENERIC_IOREMAP >> arm64: Add HAVE_IOREMAP_PROT support >> >> .../features/vm/ioremap_prot/arch-support.txt | 2 +- >> arch/arm64/Kconfig | 2 + >> arch/arm64/include/asm/io.h | 14 +-- >> arch/arm64/include/asm/pgtable.h | 10 +++ >> arch/arm64/kernel/acpi.c | 2 +- >> arch/arm64/mm/hugetlbpage.c | 10 --- >> arch/arm64/mm/ioremap.c | 86 +++---------------- >> include/asm-generic/io.h | 3 + >> mm/ioremap.c | 21 ++++- >> 9 files changed, 56 insertions(+), 94 deletions(-) > That's not a massively compelling diffstat for a cleanup, in all honesty. > I looked at generic_access_phys() to try to figure out why we would want > that on arm64, but it seems like it's related to mmap() of devices in > userspace. Bearing in mind that CONFIG_STRICT_DEVMEM=y by default, please > can you justify why this is something worth doing? The geneirc_access_phys was introduced by   7ae8ed5053a3 use generic_access_phys for /dev/mem mappings   28b2ee20c7cb access_process_vm device memory infrastructure and add into uio.c  by   7294151d0592 "uio: provide vm access to UIO_MEM_PHYS maps" It could let user to debug(eg, gdb or ptrace) app via access_process_vm(). also some upstream drivers and out-of-tree modules could use it too   drivers/fpga/dfl-afu-main.c:    .access = generic_access_phys,   drivers/pci/mmap.c:     .access = generic_access_phys, When see the ioremap_prot from generic ioremap, for better debug, I think we could enabled it on arm64 too. > Will > .