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=-8.4 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,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 1BB06CA9EB9 for ; Tue, 29 Oct 2019 06:06:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id DA44B2067D for ; Tue, 29 Oct 2019 06:06:37 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="hO1+7BoQ" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732305AbfJ2GGg (ORCPT ); Tue, 29 Oct 2019 02:06:36 -0400 Received: from us-smtp-delivery-1.mimecast.com ([205.139.110.120]:28518 "EHLO us-smtp-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1727462AbfJ2GGg (ORCPT ); Tue, 29 Oct 2019 02:06:36 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1572329194; 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=isvAQ6ZHgpnMt4TeLNZ175bqGD0B5dKkBrPR8krvorM=; b=hO1+7BoQcNu4h981GTcLzIlqI6FyhQceQwzMMwdyJGCNtAZ+VvG0V+83l8ulp/P5SexmXY 04vpfId/bTg556+naY9MLs+dQ7nwV/7WbSql+cO1z67nunpxBMTuT0Qxtbc4pAvb/XG+WR aSslSRG69j35Rs9kLNKeIOiFN0XJ7Ps= 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-242-rUX5c4-WOli5AOXP2B1buQ-1; Tue, 29 Oct 2019 02:06:30 -0400 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id D49071005500; Tue, 29 Oct 2019 06:06:28 +0000 (UTC) Received: from localhost.localdomain (ovpn-12-41.pek2.redhat.com [10.72.12.41]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 1608860BF1; Tue, 29 Oct 2019 06:06:16 +0000 (UTC) Subject: Re: [PATCH 1/2 v7] x86/kdump: always reserve the low 1MiB when the crashkernel option is specified To: Baoquan He Cc: linux-kernel@vger.kernel.org, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, hpa@zytor.com, x86@kernel.org, dyoung@redhat.com, jgross@suse.com, dhowells@redhat.com, Thomas.Lendacky@amd.com, ebiederm@xmission.com, vgoyal@redhat.com, d.hatayama@fujitsu.com, horms@verge.net.au, kexec@lists.infradead.org References: <20191029021059.22070-1-lijiang@redhat.com> <20191029021059.22070-2-lijiang@redhat.com> <20191029052842.GA7616@MiWiFi-R3L-srv> From: lijiang Message-ID: Date: Tue, 29 Oct 2019 14:06:12 +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: <20191029052842.GA7616@MiWiFi-R3L-srv> Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 X-MC-Unique: rUX5c4-WOli5AOXP2B1buQ-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=8829=E6=97=A5 13:28, Baoquan He =E5=86=99= =E9=81=93: > On 10/29/19 at 10:10am, Lianbo Jiang wrote: >> Kdump kernel will reuse the first 640k region because the real mode >> trampoline has to work in this area. When the vmcore is dumped, the >> old memory in this area may be accessed, therefore, kernel has to >> copy the contents of the first 640k area to a backup region so that >> kdump kernel can read the old memory from the backup area of the >> first 640k area, which is done in the purgatory(). >> >> But, the current handling of copying the first 640k area runs into >> problems when SME is enabled, kernel does not properly copy these >> old memory to the backup area in the purgatory(), thereby, kdump >> kernel reads out the encrypted contents, because the kdump kernel >> must access the first kernel's memory with the encryption bit set >> when SME is enabled in the first kernel. Please refer to this link: >> >> Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=3D204793 >> >> Finally, it causes the following errors, and the crash tool gets >> invalid pointers when parsing the vmcore. >> >> crash> kmem -s|grep -i invalid >> kmem: dma-kmalloc-512: slab:ffffd77680001c00 invalid freepointer:a6086ac= 099f0c5a4 >> kmem: dma-kmalloc-512: slab:ffffd77680001c00 invalid freepointer:a6086ac= 099f0c5a4 >> crash> >> >> To avoid the above errors, when the crashkernel option is specified, >> lets reserve the remaining low 1MiB memory(after reserving real mode >> memory) so that the allocated memory does not fall into the low 1MiB >> area, which makes us not to copy the first 640k content to a backup >> region in purgatory(). This indicates that it does not need to be >> included in crash dumps or used for anything except the processor >> trampolines that must live in the low 1MiB. >> >> Signed-off-by: Lianbo Jiang >> --- >> arch/x86/include/asm/crash.h | 6 ++++++ >> arch/x86/kernel/crash.c | 15 +++++++++++++++ >> arch/x86/realmode/init.c | 2 ++ >> 3 files changed, 23 insertions(+) >> >> diff --git a/arch/x86/include/asm/crash.h b/arch/x86/include/asm/crash.h >> index 0acf5ee45a21..3e966a3dc823 100644 >> --- a/arch/x86/include/asm/crash.h >> +++ b/arch/x86/include/asm/crash.h >> @@ -8,4 +8,10 @@ int crash_setup_memmap_entries(struct kimage *image, >> =09=09struct boot_params *params); >> void crash_smp_send_stop(void); >> =20 >> +#ifdef CONFIG_KEXEC_CORE >> +void __init kexec_reserve_low_1MiB(void); >> +#else >> +static inline void __init kexec_reserve_low_1MiB(void) { } >> +#endif >> + >> #endif /* _ASM_X86_CRASH_H */ >> diff --git a/arch/x86/kernel/crash.c b/arch/x86/kernel/crash.c >> index eb651fbde92a..144f519aef29 100644 >> --- a/arch/x86/kernel/crash.c >> +++ b/arch/x86/kernel/crash.c >> @@ -24,6 +24,7 @@ >> #include >> #include >> #include >> +#include >> =20 >> #include >> #include >> @@ -39,6 +40,7 @@ >> #include >> #include >> #include >> +#include >> =20 >> /* Used while preparing memory map entries for second kernel */ >> struct crash_memmap_data { >> @@ -68,6 +70,19 @@ static inline void cpu_crash_vmclear_loaded_vmcss(voi= d) >> =09rcu_read_unlock(); >> } >> =20 >> +/* >> + * When the crashkernel option is specified, only use the low >> + * 1MiB for the real mode trampoline. >> + */ >> +void __init kexec_reserve_low_1MiB(void) >=20 > Thanks for the effort, Lianbo. I believe everyone is confident with this > solution and fix. >=20 > I have a tiny concern, why the function name is > kexec_reserve_low_1MiB(), but not kexec_reserve_low_1M()? Thanks for your comment, Baoquan. It means that kernel will reserve 1M 'Byte' memory, the function name does = not have special meaning. Would you mind if i change it to the crash_reserve_low_1M()? void __init crash_reserve_low_1M(void) Thanks. Lianbo > I searched in kernel code with below filter, didn't see MiB appearing in > a function name. I am not sure about it either, just ask. >=20 > git grep "_[1-9]*M " arch/ kernel/ mm include/ drivers/ net/ init fs cryp= to/ certs/ ipc lib >=20 > Thanks > Baoquan >=20 >> +{ >> +=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} >> +} >> + >> #if defined(CONFIG_SMP) && defined(CONFIG_X86_LOCAL_APIC) >> =20 >> static void kdump_nmi_callback(int cpu, struct pt_regs *regs) >> diff --git a/arch/x86/realmode/init.c b/arch/x86/realmode/init.c >> index 7dce39c8c034..b8bbd0017ca8 100644 >> --- a/arch/x86/realmode/init.c >> +++ b/arch/x86/realmode/init.c >> @@ -8,6 +8,7 @@ >> #include >> #include >> #include >> +#include >> =20 >> struct real_mode_header *real_mode_header; >> u32 *trampoline_cr4_features; >> @@ -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) >> --=20 >> 2.17.1 >>