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 D6CD5CA9EB9 for ; Tue, 29 Oct 2019 05:28:58 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 9F67920830 for ; Tue, 29 Oct 2019 05:28:58 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="hqN/bKWI" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731952AbfJ2F25 (ORCPT ); Tue, 29 Oct 2019 01:28:57 -0400 Received: from us-smtp-2.mimecast.com ([205.139.110.61]:23287 "EHLO us-smtp-delivery-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1728312AbfJ2F25 (ORCPT ); Tue, 29 Oct 2019 01:28:57 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1572326934; 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=sFd2Bl9e+kdHwn6Jb/1ywBIhlMiwzG512GuG+Pa19cA=; b=hqN/bKWIyZCfU2/MUtH0syiBNDn4czx/xUhbCL5uNh6gjW3xluJgf4EEGNOx208eT8e+Cg tjqMrZounjH15nMnEuB7jRosKq6f0hAFEcOp70PucXy4CgJMzoxqqbnE5I0TZA5eIlmO73 y7L8NZmZbb+50sPVyGGeZKwxfyiK6go= 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-428-t1c6jkXuOPi7SXrPPUDeEA-1; Tue, 29 Oct 2019 01:28:51 -0400 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 578A7801E64; Tue, 29 Oct 2019 05:28:49 +0000 (UTC) Received: from localhost (ovpn-12-27.pek2.redhat.com [10.72.12.27]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 581635C1B2; Tue, 29 Oct 2019 05:28:45 +0000 (UTC) Date: Tue, 29 Oct 2019 13:28:42 +0800 From: Baoquan He To: Lianbo Jiang 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 Subject: Re: [PATCH 1/2 v7] x86/kdump: always reserve the low 1MiB when the crashkernel option is specified Message-ID: <20191029052842.GA7616@MiWiFi-R3L-srv> References: <20191029021059.22070-1-lijiang@redhat.com> <20191029021059.22070-2-lijiang@redhat.com> MIME-Version: 1.0 In-Reply-To: <20191029021059.22070-2-lijiang@redhat.com> User-Agent: Mutt/1.10.1 (2018-07-13) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 X-MC-Unique: t1c6jkXuOPi7SXrPPUDeEA-1 X-Mimecast-Spam-Score: 0 Content-Type: text/plain; charset=WINDOWS-1252 Content-Transfer-Encoding: quoted-printable Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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(). >=20 > 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: >=20 > Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=3D204793 >=20 > Finally, it causes the following errors, and the crash tool gets > invalid pointers when parsing the vmcore. >=20 > crash> kmem -s|grep -i invalid > kmem: dma-kmalloc-512: slab:ffffd77680001c00 invalid freepointer:a6086ac0= 99f0c5a4 > kmem: dma-kmalloc-512: slab:ffffd77680001c00 invalid freepointer:a6086ac0= 99f0c5a4 > crash> >=20 > 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. >=20 > 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(+) >=20 > 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(void= ) > =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) Thanks for the effort, Lianbo. I believe everyone is confident with this solution and fix. I have a tiny concern, why the function name is kexec_reserve_low_1MiB(), but not kexec_reserve_low_1M()? 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. git grep "_[1-9]*M " arch/ kernel/ mm include/ drivers/ net/ init fs crypto= / certs/ ipc lib Thanks Baoquan > +{ > +=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 >=20