From mboxrd@z Thu Jan 1 00:00:00 1970 From: takahiro.akashi@linaro.org (AKASHI Takahiro) Date: Tue, 20 Sep 2016 17:27:37 +0900 Subject: [PATCH v26 6/7] arm64: kdump: update a kernel doc In-Reply-To: <57DC18FC.9000807@arm.com> References: <20160907042908.6232-1-takahiro.akashi@linaro.org> <20160907042908.6232-7-takahiro.akashi@linaro.org> <57DC18FC.9000807@arm.com> Message-ID: <20160920082736.GE30248@linaro.org> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Fri, Sep 16, 2016 at 05:08:28PM +0100, James Morse wrote: > Hi Akashi, > > On 07/09/16 05:29, AKASHI Takahiro wrote: > > This patch adds arch specific descriptions about kdump usage on arm64 > > to kdump.txt. > > > diff --git a/Documentation/kdump/kdump.txt b/Documentation/kdump/kdump.txt > > > @@ -249,6 +249,13 @@ Dump-capture kernel config options (Arch Dependent, arm) > > > > AUTO_ZRELADDR=y > > > > +Dump-capture kernel config options (Arch Dependent, arm64) > > +---------------------------------------------------------- > > + > > +- Please note that kvm of the dump-capture kernel will not be enabled > > + on non-VHE systems even if it is configured. This is because the CPU > > + cannot be reset to EL2 on panic. > > Nit: > cannot be -> will not be OK. > We could try to do this, but its more code that could prevent us reaching the > kdump kernel, so we choose not to. > > > > @@ -370,6 +381,9 @@ For s390x: > > For arm: > > "1 maxcpus=1 reset_devices" > > > > +For arm64: > > + "1 maxcpus=1 reset_devices" > > + > > 'maxcpus=1' is a bit fragile. Since 44dbcc93ab67145 ("arm64: Fix behavior of > maxcpus=N") udev on ubuntu vivid (running on Juno) has taken it upon itself to > bring the secondary cores online, even when booted with 'maxcpus=1'. > > Can we change the recomendation to "1 nosmp reset_devices"? Well, I have no strong opinion here, but I'm not quite sure whether this change does make any difference in practice. Looking at kernel/smp.c, the only difference is setup_max_cpus. But given that arch_disable_smp_support() is null and smp_cpus_done() ignores "max_cpus" on arm64, I don't think that the change is very meaningful. I might miss something. Thanks, -Takahiro AKASHI > > Thanks, > > James > From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from mail-pa0-x229.google.com ([2607:f8b0:400e:c03::229]) by bombadil.infradead.org with esmtps (Exim 4.85_2 #1 (Red Hat Linux)) id 1bmGIO-00042V-1A for kexec@lists.infradead.org; Tue, 20 Sep 2016 08:20:53 +0000 Received: by mail-pa0-x229.google.com with SMTP id oz2so4738804pac.2 for ; Tue, 20 Sep 2016 01:20:31 -0700 (PDT) Date: Tue, 20 Sep 2016 17:27:37 +0900 From: AKASHI Takahiro Subject: Re: [PATCH v26 6/7] arm64: kdump: update a kernel doc Message-ID: <20160920082736.GE30248@linaro.org> References: <20160907042908.6232-1-takahiro.akashi@linaro.org> <20160907042908.6232-7-takahiro.akashi@linaro.org> <57DC18FC.9000807@arm.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <57DC18FC.9000807@arm.com> List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "kexec" Errors-To: kexec-bounces+dwmw2=infradead.org@lists.infradead.org To: James Morse Cc: mark.rutland@arm.com, geoff@infradead.org, catalin.marinas@arm.com, will.deacon@arm.com, bauerman@linux.vnet.ibm.com, dyoung@redhat.com, kexec@lists.infradead.org, linux-arm-kernel@lists.infradead.org On Fri, Sep 16, 2016 at 05:08:28PM +0100, James Morse wrote: > Hi Akashi, > > On 07/09/16 05:29, AKASHI Takahiro wrote: > > This patch adds arch specific descriptions about kdump usage on arm64 > > to kdump.txt. > > > diff --git a/Documentation/kdump/kdump.txt b/Documentation/kdump/kdump.txt > > > @@ -249,6 +249,13 @@ Dump-capture kernel config options (Arch Dependent, arm) > > > > AUTO_ZRELADDR=y > > > > +Dump-capture kernel config options (Arch Dependent, arm64) > > +---------------------------------------------------------- > > + > > +- Please note that kvm of the dump-capture kernel will not be enabled > > + on non-VHE systems even if it is configured. This is because the CPU > > + cannot be reset to EL2 on panic. > > Nit: > cannot be -> will not be OK. > We could try to do this, but its more code that could prevent us reaching the > kdump kernel, so we choose not to. > > > > @@ -370,6 +381,9 @@ For s390x: > > For arm: > > "1 maxcpus=1 reset_devices" > > > > +For arm64: > > + "1 maxcpus=1 reset_devices" > > + > > 'maxcpus=1' is a bit fragile. Since 44dbcc93ab67145 ("arm64: Fix behavior of > maxcpus=N") udev on ubuntu vivid (running on Juno) has taken it upon itself to > bring the secondary cores online, even when booted with 'maxcpus=1'. > > Can we change the recomendation to "1 nosmp reset_devices"? Well, I have no strong opinion here, but I'm not quite sure whether this change does make any difference in practice. Looking at kernel/smp.c, the only difference is setup_max_cpus. But given that arch_disable_smp_support() is null and smp_cpus_done() ignores "max_cpus" on arm64, I don't think that the change is very meaningful. I might miss something. Thanks, -Takahiro AKASHI > > Thanks, > > James > _______________________________________________ kexec mailing list kexec@lists.infradead.org http://lists.infradead.org/mailman/listinfo/kexec