From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="BwWuuSDS" Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9E17C191 for ; Wed, 22 Nov 2023 01:34:44 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1700645683; 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=+OTgZltwB2ZS+YZyn6PYgFPXeR3pdRlWkz0aWS8O4HE=; b=BwWuuSDSvBZX8Mo7G/uzuxwxVixnrmmdqUnkZx0OtwE1DVMH27AH4c6jJvXbP/BVBm2pnd 77sZlTm5mtm89rkaBPL3o9nnd+bXlfVH6dL/cYz2vincEezSthdFNVSkUO8hR+dnyun2so bzfx4LydAh4Vj2wfqlYfnQ+tbldTuWc= Received: from mimecast-mx02.redhat.com (mx-ext.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-591-_biuZLCONCOAsgDXiclx4A-1; Wed, 22 Nov 2023 04:34:40 -0500 X-MC-Unique: _biuZLCONCOAsgDXiclx4A-1 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.rdu2.redhat.com [10.11.54.7]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 8960E3C0FCA6; Wed, 22 Nov 2023 09:34:39 +0000 (UTC) Received: from localhost (unknown [10.72.112.97]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 2A80F1C060AE; Wed, 22 Nov 2023 09:34:36 +0000 (UTC) Date: Wed, 22 Nov 2023 17:34:33 +0800 From: Baoquan He To: Ignat Korchagin Cc: eric_devolder@yahoo.com, linux@armlinux.org.uk, catalin.marinas@arm.com, will@kernel.org, chenhuacai@kernel.org, geert@linux-m68k.org, tsbogend@alpha.franken.de, James Bottomley , deller@gmx.de, ysato@users.sourceforge.jp, dalias@libc.org, glaubitz@physik.fu-berlin.de, Thomas Gleixner , Ingo Molnar , Borislav Petkov , dave.hansen@linux.intel.com, x86@kernel.org, linux-kernel , linux-arm-kernel@lists.infradead.org, linux-ia64@vger.kernel.org, loongarch@lists.linux.dev, linux-m68k@lists.linux-m68k.org, linux-mips@vger.kernel.org, linux-parisc@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-riscv@lists.infradead.org, linux-s390@vger.kernel.org, linux-sh@vger.kernel.org, kernel@xen0n.name, mpe@ellerman.id.au, npiggin@gmail.com, christophe.leroy@csgroup.eu, paul.walmsley@sifive.com, palmer@dabbelt.com, aou@eecs.berkeley.edu, hca@linux.ibm.com, gor@linux.ibm.com, agordeev@linux.ibm.com, borntraeger@linux.ibm.com, svens@linux.ibm.com, hpa@zytor.com, keescook@chromium.org, paulmck@kernel.org, Peter Zijlstra , frederic@kernel.org, Andrew Morton , Ard Biesheuvel , samitolvanen@google.com, juerg.haefliger@canonical.com, arnd@arndb.de, rmk+kernel@armlinux.org.uk, linus.walleij@linaro.org, sebastian.reichel@collabora.com, rppt@kernel.org, kirill.shutemov@linux.intel.com, anshuman.khandual@arm.com, ziy@nvidia.com, masahiroy@kernel.org, ndesaulniers@google.com, mhiramat@kernel.org, ojeda@kernel.org, thunder.leizhen@huawei.com, xin3.li@intel.com, tj@kernel.org, Greg KH , tsi@tuyoix.net, hbathini@linux.ibm.com, sourabhjain@linux.ibm.com, boris.ostrovsky@oracle.com, konrad.wilk@oracle.com, kernel-team Subject: Re: Potential config regression after 89cde455 ("kexec: consolidate kexec and crash options into kernel/Kconfig.kexec") Message-ID: References: Precedence: bulk X-Mailing-List: linux-sh@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.7 On 11/21/23 at 09:43am, Ignat Korchagin wrote: > On Tue, Nov 21, 2023 at 7:53 AM Ignat Korchagin wrote: > > > > On Tue, Nov 21, 2023 at 1:50 AM Baoquan He wrote: > > > > > > Eric DeVolder's Oracle mail address is not available anymore, add his > > > current mail address he told me. > > > > Thank you! > > > > > On 11/20/23 at 10:52pm, Ignat Korchagin wrote: > > > > Good day! > > > > > > > > We have recently started to evaluate Linux 6.6 and noticed that we > > > > cannot disable CONFIG_KEXEC anymore, but keep CONFIG_CRASH_DUMP > > > > enabled. It seems to be related to commit 89cde455 ("kexec: > > > > consolidate kexec and crash options into kernel/Kconfig.kexec"), where > > > > a CONFIG_KEXEC dependency was added to CONFIG_CRASH_DUMP. > > > > > > > > In our current kernel (Linux 6.1) we only enable CONFIG_KEXEC_FILE > > > > with enforced signature check to support the kernel crash dumping > > > > functionality and would like to keep CONFIG_KEXEC disabled for > > > > security reasons [1]. > > > > > > > > I was reading the long commit message, but the reason for adding > > > > CONFIG_KEXEC as a dependency for CONFIG_CRASH_DUMP evaded me. And I > > > > believe from the implementation perspective CONFIG_KEXEC_FILE should > > > > suffice here (as we successfully used it for crashdumps on Linux 6.1). > > > > > > > > Is there a reason for adding this dependency or is it just an > > > > oversight? Would some solution of requiring either CONFIG_KEXEC or > > > > CONFIG_KEXEC_FILE work here? > > > > > > I searched the patch history, found Eric didn't add the dependency on > > > CONFIG_KEXEC at the beginning. Later a linux-next building failure with > > > randconfig was reported, in there CONFIG_CRASH_DUMP enabled, while > > > CONFIG_KEXEC is disabled. Finally Eric added the KEXEC dependency for > > > CRASH_DUMP. Please see below link for more details: > > > > > > https://lore.kernel.org/all/3e8eecd1-a277-2cfb-690e-5de2eb7b988e@oracle.com/T/#u > > > > Thank you for digging this up. However I'm still confused, because > > this is exactly how we configure Linux 6.1 (although we do have > > CONFIG_KEXEC_FILE enabled) and we don't have any problems. I believe > > we did not investigate this issue properly. > > I did some preliminary investigation for this. If I patch out the > dependency on CONFIG_KEXEC the kernel builds just fine for x86 > (without CONFIG_CRASH_HOTPLUG - which is probably another issue) - so > this was the previous behaviour. I can see that the reported error is > for arm architecture and was able to reproduce it with a simple cross > compiler in Debian. However, I think it is still somehow related to > this patchset as the previous kernels (up to 6.5) build fine with just > CONFIG_CRASH_DUMP and without CONFIG_KEXEC for arm as well. So even > for arm it was introduced in 6.6. Thanks for the information. I haven't run the reproducer of issue reported on Eric's old patchset, while checkout to kernel 6.1, only s390 selected KEXEC for CRASH_DUMP already. And with the ARM building breakage, the simplest idea is to select KEXEC only for ARM or S390 CRASH_DUMP. I plan to try the reproducer later. If you have any idea or draft patch, please feel free to post. diff --git a/kernel/Kconfig.kexec b/kernel/Kconfig.kexec index 7aff28ded2f4..382dcd8d7a9d 100644 --- a/kernel/Kconfig.kexec +++ b/kernel/Kconfig.kexec @@ -97,7 +97,7 @@ config CRASH_DUMP depends on ARCH_SUPPORTS_KEXEC select CRASH_CORE select KEXEC_CORE - select KEXEC + select KEXEC if (ARM || S390) arch/s390/Kconfig in kernel 6.1: config CRASH_DUMP bool "kernel crash dumps" select KEXEC help Generate crash dump after being started by kexec. Crash dump kernels are loaded in the main kernel with kexec-tools into a specially reserved region and then later executed after a crash by kdump/kexec. Refer to for more details on this. This option also enables s390 zfcpdump. See also > > > > And besides, the newly added CONFIG_CRASH_HOTPLUG also needs > > > CONFIG_KEXEC if the elfcorehdr is allowed to be manipulated when > > > cpu/memory hotplug hapened. > > > > This still feels like a regression to me: any crash dump support > > should be independent of KEXEC syscalls being present. While probably > > the common case (including us) that the crashing kernel and recovery > > kernel are the same, they don't have to be. We need kexec syscall in > > the crashing kernel, but crashdump support in the recovery kernel (but > > the recovery kernel not having the kexec syscalls should be totally > > fine). If we do require some code definitions from kexec - at most we > > should put them under CONFIG_KEXEC_CORE. > > > > > Thanks > > > Baoquan > > > > > Ignat >