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 X-Spam-Level: X-Spam-Status: No, score=-5.3 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 90375CA9EA0 for ; Fri, 25 Oct 2019 08:53:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 5E1EC21D71 for ; Fri, 25 Oct 2019 08:53:26 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="L1lYxeAr" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2437873AbfJYIxZ (ORCPT ); Fri, 25 Oct 2019 04:53:25 -0400 Received: from us-smtp-delivery-1.mimecast.com ([207.211.31.120]:30354 "EHLO us-smtp-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S2437271AbfJYIxY (ORCPT ); Fri, 25 Oct 2019 04:53:24 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1571993602; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=WQrk6OLVhPcjkhSKChmWeNmbh5o1KSL0MTHhKDkF+0Y=; b=L1lYxeArVY48QwCbwrtDVc1sqGPJrqveb2enK2lqXapn6l8qU1qceWwBeJALm+Inp056h3 oSoNjjr8QWoqAhGt5T3tTwaR2zlpdSPXkeC1/7Jwek5ODyzYeUD56o12xCFIQC0bw6pmlK mSM1BrX+yIQ+a6PK602P0z5BaXozfjE= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-263-yX8zK2g7N4eEB9MXdyiWXA-1; Fri, 25 Oct 2019 04:53:16 -0400 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id DFE1D80183D; Fri, 25 Oct 2019 08:53:14 +0000 (UTC) Received: from localhost.localdomain (ovpn-12-33.pek2.redhat.com [10.72.12.33]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 0D73510013A1; Fri, 25 Oct 2019 08:53:00 +0000 (UTC) Subject: Re: [PATCH 1/2 v5] x86/kdump: always reserve the low 1MiB when the crashkernel option is specified To: "Eric W. Biederman" Cc: "d.hatayama@fujitsu.com" , Simon Horman , "linux-kernel@vger.kernel.org" , "jgross@suse.com" , "Thomas.Lendacky@amd.com" , "bhe@redhat.com" , "x86@kernel.org" , "kexec@lists.infradead.org" , "dhowells@redhat.com" , "mingo@redhat.com" , "bp@alien8.de" , "hpa@zytor.com" , "tglx@linutronix.de" , "dyoung@redhat.com" , "vgoyal@redhat.com" References: <20191023141912.29110-1-lijiang@redhat.com> <20191023141912.29110-2-lijiang@redhat.com> <20191024100719.GC11441@verge.net.au> <4c1c4b78-23f0-a2b9-4be7-5bab0335f10a@redhat.com> <6da13645-c5e9-6c95-1f2d-bede177f9863@redhat.com> <2020bbf9-67b2-52e8-756f-b595414b4c02@redhat.com> <875zkdtrw0.fsf@x220.int.ebiederm.org> From: lijiang Message-ID: <021215d1-af6e-d032-6d37-fcc2cf30c613@redhat.com> Date: Fri, 25 Oct 2019 16:52:55 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: <875zkdtrw0.fsf@x220.int.ebiederm.org> Content-Language: en-US X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 X-MC-Unique: yX8zK2g7N4eEB9MXdyiWXA-1 X-Mimecast-Spam-Score: 0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org =E5=9C=A8 2019=E5=B9=B410=E6=9C=8825=E6=97=A5 11:39, Eric W. Biederman =E5= =86=99=E9=81=93: > lijiang writes: >=20 >> * Returns the length of the argument (regardless of if it was >> * truncated to fit in the buffer), or -1 on not found. >> */ >> static int >> __cmdline_find_option(const char *cmdline, int max_cmdline_size, >> const char *option, char *buffer, int bufsize) >> >> >> According to the above code comment, it should be better like this: >> >> + if (cmdline_find_option(boot_command_line, "crashkernel", >> + NULL, 0) > 0) { >> >> After i test, i will post again. >> >=20 > This seems reasonable as we are dealing with x86 only code. >=20 When we compile the non-x86 kernel, that could cause the the compile error because the cmdline_find_option() won't be defined on non-x86 architecture. So i will define a weak function in the kernel/kexec_core.c like this: + +void __init __weak kexec_reserve_low_1MiB(void) +{} and implement the kexec_reserve_low_1MiB() in the arch/x86/kernel/machine_k= exec_64.c. +/* + * When the crashkernel option is specified, only use the low + * 1MiB for the real mode trampoline. + */ +void __init kexec_reserve_low_1MiB(void) +{ + if (cmdline_find_option(boot_command_line, "crashkernel", + NULL, 0) > 0) { + memblock_reserve(0, 1<<20); + pr_info("Reserving the low 1MiB of memory for crashkernel\n= "); + } +}=20 That will solve the compile error on the non-x86 kernel, and it also works = well on the x86 kernel. BTW: i pasted the code at the end, please refer to it. > It wound be nice if someone could generalize cmdline_find_option to be > arch independent so that crash_core.c:parse_crashkernel could use it. Good point, that could be done in the future. > I don't think for this patchset, but it looks like an overdue cleanup. >=20 > We run the risk with parse_crashkernel using strstr and this using > another algorithm of having different kernel command line parsers > giving different results and disagreeing if "crashkernel=3D" is present > or not on the kernel command line. >=20 Indeed, but sometimes, the crashkernel has a complicated syntax, maybe that could be a reason. Thanks. Lianbo > Eric >=20 >=20 --- arch/x86/kernel/machine_kexec_64.c | 15 +++++++++++++++ arch/x86/realmode/init.c | 2 ++ include/linux/kexec.h | 2 ++ kernel/kexec_core.c | 3 +++ 4 files changed, 22 insertions(+) diff --git a/arch/x86/kernel/machine_kexec_64.c b/arch/x86/kernel/machine_k= exec_64.c index 5dcd438ad8f2..42d7c15c45f1 100644 --- a/arch/x86/kernel/machine_kexec_64.c +++ b/arch/x86/kernel/machine_kexec_64.c @@ -17,6 +17,7 @@ #include #include #include +#include =20 #include #include @@ -27,6 +28,7 @@ #include #include #include +#include =20 #ifdef CONFIG_ACPI /* @@ -687,3 +689,16 @@ void arch_kexec_pre_free_pages(void *vaddr, unsigned i= nt pages) =09 */ =09set_memory_encrypted((unsigned long)vaddr, pages); } + +/* + * When the crashkernel option is specified, only use the low + * 1MiB for the real mode trampoline. + */ +void __init kexec_reserve_low_1MiB(void) +{ +=09if (cmdline_find_option(boot_command_line, "crashkernel", +=09=09=09=09NULL, 0) > 0) { +=09=09memblock_reserve(0, 1<<20); +=09=09pr_info("Reserving the low 1MiB of memory for crashkernel\n"); +=09} +} diff --git a/arch/x86/realmode/init.c b/arch/x86/realmode/init.c index 7dce39c8c034..064cc79a015d 100644 --- a/arch/x86/realmode/init.c +++ b/arch/x86/realmode/init.c @@ -3,6 +3,7 @@ #include #include #include +#include =20 #include #include @@ -34,6 +35,7 @@ void __init reserve_real_mode(void) =20 =09memblock_reserve(mem, size); =09set_real_mode_mem(mem); +=09kexec_reserve_low_1MiB(); } =20 static void __init setup_real_mode(void) diff --git a/include/linux/kexec.h b/include/linux/kexec.h index 1776eb2e43a4..988bf2de51a7 100644 --- a/include/linux/kexec.h +++ b/include/linux/kexec.h @@ -306,6 +306,7 @@ extern void __crash_kexec(struct pt_regs *); extern void crash_kexec(struct pt_regs *); int kexec_should_crash(struct task_struct *); int kexec_crash_loaded(void); +void __init kexec_reserve_low_1MiB(void); void crash_save_cpu(struct pt_regs *regs, int cpu); extern int kimage_crash_copy_vmcoreinfo(struct kimage *image); =20 @@ -397,6 +398,7 @@ static inline void __crash_kexec(struct pt_regs *regs) = { } static inline void crash_kexec(struct pt_regs *regs) { } static inline int kexec_should_crash(struct task_struct *p) { return 0; } static inline int kexec_crash_loaded(void) { return 0; } +static inline void __init kexec_reserve_low_1MiB(void) { } #define kexec_in_progress false #endif /* CONFIG_KEXEC_CORE */ =20 diff --git a/kernel/kexec_core.c b/kernel/kexec_core.c index 15d70a90b50d..8856047bcdc8 100644 --- a/kernel/kexec_core.c +++ b/kernel/kexec_core.c @@ -1213,3 +1213,6 @@ void __weak arch_kexec_protect_crashkres(void) =20 void __weak arch_kexec_unprotect_crashkres(void) {} + +void __init __weak kexec_reserve_low_1MiB(void) +{} --=20 2.17.1