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 0BEE9C433EF for ; Wed, 11 May 2022 09:52:12 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236490AbiEKJwI (ORCPT ); Wed, 11 May 2022 05:52:08 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46866 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S238629AbiEKJvP (ORCPT ); Wed, 11 May 2022 05:51:15 -0400 Received: from szxga03-in.huawei.com (szxga03-in.huawei.com [45.249.212.189]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9191031350; Wed, 11 May 2022 02:50:54 -0700 (PDT) Received: from dggpemm500022.china.huawei.com (unknown [172.30.72.53]) by szxga03-in.huawei.com (SkyGuard) with ESMTP id 4KyqmF1nTWzCsdt; Wed, 11 May 2022 17:46:05 +0800 (CST) Received: from dggpemm500006.china.huawei.com (7.185.36.236) by dggpemm500022.china.huawei.com (7.185.36.162) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.24; Wed, 11 May 2022 17:50:52 +0800 Received: from [10.174.178.55] (10.174.178.55) by dggpemm500006.china.huawei.com (7.185.36.236) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.24; Wed, 11 May 2022 17:50:51 +0800 Subject: Re: [PATCH] arm64: kdump: Do not allocate crash low memory if not needed To: Baoquan He CC: Dave Young , Vivek Goyal , , , Catalin Marinas , Will Deacon , , Jonathan Corbet , , "Eric W . Biederman" , Randy Dunlap , Feng Zhou , Kefeng Wang , Chen Zhou , John Donnelly , "Dave Kleikamp" References: <20220511032033.426-1-thunder.leizhen@huawei.com> From: "Leizhen (ThunderTown)" Message-ID: <8922e61e-ab7c-6e48-ad8c-57b75156a0f2@huawei.com> Date: Wed, 11 May 2022 17:50:51 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:60.0) Gecko/20100101 Thunderbird/60.7.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [10.174.178.55] X-ClientProxiedBy: dggems706-chm.china.huawei.com (10.3.19.183) To dggpemm500006.china.huawei.com (7.185.36.236) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2022/5/11 17:06, Baoquan He wrote: > On 05/11/22 at 11:20am, Zhen Lei wrote: >> When "crashkernel=X,high" is specified, the specified "crashkernel=Y,low" >> memory is not required in the following corner cases: >> 1. If both CONFIG_ZONE_DMA and CONFIG_ZONE_DMA32 are disabled, it means >> that the devices can access any memory. >> 2. If the system memory is small, the crash high memory may be allocated >> from the DMA zones. If that happens, there's no need to allocate >> another crash low memory because there's already one. >> >> Add condition '(crash_base >= CRASH_ADDR_LOW_MAX)' to determine whether >> the 'high' memory is allocated above DMA zones. Note: when both >> CONFIG_ZONE_DMA and CONFIG_ZONE_DMA32 are disabled, the entire physical >> memory is DMA accessible, CRASH_ADDR_LOW_MAX equals 'PHYS_MASK + 1'. >> >> Signed-off-by: Zhen Lei >> --- >> Documentation/admin-guide/kernel-parameters.txt | 5 +++-- >> arch/arm64/mm/init.c | 3 ++- >> 2 files changed, 5 insertions(+), 3 deletions(-) >> >> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt >> index f6ff55840751a78..1b543c3109f4851 100644 >> --- a/Documentation/admin-guide/kernel-parameters.txt >> +++ b/Documentation/admin-guide/kernel-parameters.txt >> @@ -823,7 +823,7 @@ >> low memory is needed to make sure DMA buffers for 32-bit >> devices won't run out. Kernel would try to allocate >> at least 256M below 4G automatically. >> - This one let user to specify own low range under 4G >> + This one lets the user specify own low range under 4G > ~ This one let users specify own low range ... > > Other than this nitpick, LGTM This is Catalin's response a few days ago: Slightly more correct is "This one lets the user specify..." I didn't googled "This one lets", but I googled "It lets". I think he wrote it right. Both "the user" and "users" seem to be right. > > Acked-by: Baoquan He > >> for second kernel instead. >> 0: to disable low allocation. >> It will be ignored when crashkernel=X,high is not used >> @@ -832,7 +832,8 @@ >> [KNL, ARM64] range in low memory. >> This one lets the user specify a low range in the >> DMA zone for the crash dump kernel. >> - It will be ignored when crashkernel=X,high is not used. >> + It will be ignored when crashkernel=X,high is not used >> + or memory reserved is located in the DMA zones. >> >> cryptomgr.notests >> [KNL] Disable crypto self-tests >> diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c >> index 18ba66c90991ea0..ac510fb6a2c0189 100644 >> --- a/arch/arm64/mm/init.c >> +++ b/arch/arm64/mm/init.c >> @@ -170,7 +170,8 @@ static void __init reserve_crashkernel(void) >> return; >> } >> >> - if (crash_low_size && reserve_crashkernel_low(crash_low_size)) { >> + if ((crash_base >= CRASH_ADDR_LOW_MAX) && >> + crash_low_size && reserve_crashkernel_low(crash_low_size)) { >> memblock_phys_free(crash_base, crash_size); >> return; >> } >> -- >> 2.25.1 >> > > . > -- Regards, Zhen Lei