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 99E75C433FE for ; Tue, 8 Nov 2022 02:06:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232196AbiKHCGn (ORCPT ); Mon, 7 Nov 2022 21:06:43 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44690 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232060AbiKHCGm (ORCPT ); Mon, 7 Nov 2022 21:06:42 -0500 Received: from szxga03-in.huawei.com (szxga03-in.huawei.com [45.249.212.189]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E2D0C13CEE; Mon, 7 Nov 2022 18:06:41 -0800 (PST) Received: from dggpemm500022.china.huawei.com (unknown [172.30.72.56]) by szxga03-in.huawei.com (SkyGuard) with ESMTP id 4N5rx81X4gzJnYV; Tue, 8 Nov 2022 10:03:40 +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 15.1.2375.31; Tue, 8 Nov 2022 10:06:40 +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 15.1.2375.31; Tue, 8 Nov 2022 10:06:39 +0800 Subject: Re: [PATCH v3 2/2] arm64: kdump: Support crashkernel=X fall back to reserve region above DMA zones To: Catalin Marinas CC: Dave Young , Baoquan He , Vivek Goyal , , , Will Deacon , , Jonathan Corbet , , "Eric W . Biederman" , Randy Dunlap , Feng Zhou , Kefeng Wang , Chen Zhou , John Donnelly , "Dave Kleikamp" References: <20220711090319.1604-1-thunder.leizhen@huawei.com> <20220711090319.1604-3-thunder.leizhen@huawei.com> From: "Leizhen (ThunderTown)" Message-ID: <6b20a203-6aab-2b87-9b95-814aeb79b5bd@huawei.com> Date: Tue, 8 Nov 2022 10:06:38 +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: dggems702-chm.china.huawei.com (10.3.19.179) To dggpemm500006.china.huawei.com (7.185.36.236) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-doc@vger.kernel.org On 2022/11/8 1:13, Catalin Marinas wrote: > On Mon, Jul 11, 2022 at 05:03:19PM +0800, Zhen Lei wrote: >> diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c >> index 5390f361208ccf7..8539598f9e58b4d 100644 >> --- a/arch/arm64/mm/init.c >> +++ b/arch/arm64/mm/init.c >> @@ -138,6 +138,7 @@ static void __init reserve_crashkernel(void) >> unsigned long long crash_max = CRASH_ADDR_LOW_MAX; >> char *cmdline = boot_command_line; >> int ret; >> + bool fixed_base; >> >> if (!IS_ENABLED(CONFIG_KEXEC_CORE)) >> return; >> @@ -166,15 +167,28 @@ static void __init reserve_crashkernel(void) >> return; >> } >> >> + fixed_base = !!crash_base; >> crash_size = PAGE_ALIGN(crash_size); >> >> /* User specifies base address explicitly. */ >> - if (crash_base) >> + if (fixed_base) >> crash_max = crash_base + crash_size; > > Not a fan of '!!', it is converted automatically. If you don't like the > conversion, just initialise fixed_base to false and here: > > if (crash_base) { > fixed_base = true; OK, This way would be better. > crash_max = crash_base + crash_size; > } > >> +retry: >> crash_base = memblock_phys_alloc_range(crash_size, CRASH_ALIGN, >> crash_base, crash_max); >> if (!crash_base) { >> + /* >> + * Attempt to fully allocate low memory failed, fall back >> + * to high memory, the minimum required low memory will be >> + * reserved later. >> + */ > > I'm not sure this comment makes sense. If !crash_base, it doesn't mean > the kernel failed to fully allocate low memory. crash_max here could be > CRASH_ADDR_HIGH_MAX if crashkerne=X,high was specified. Maybe says > something like "If the first attempt was for low memory, fall back to > high ..." This description is accurate. I'll update. Thanks. > >> + if (!fixed_base && (crash_max == CRASH_ADDR_LOW_MAX)) { >> + crash_max = CRASH_ADDR_HIGH_MAX; >> + crash_low_size = DEFAULT_CRASH_KERNEL_LOW_SIZE; >> + goto retry; >> + } > > The retry logic looks fine, it only happens once as crash_max is > updated. > -- Regards, Zhen Lei