From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Message-ID: <51FA8C13.2060807@wwwdotorg.org> Date: Thu, 01 Aug 2013 10:25:55 -0600 From: Stephen Warren MIME-Version: 1.0 Subject: Re: [PATCH] ARM: kexec: offline non panic CPUs on Kdump panic References: <1374817287-27952-1-git-send-email-vijay.kilari@gmail.com> <20130726104908.GC17886@mudshark.cambridge.arm.com> <51F2ACF7.9000008@wwwdotorg.org> <51F7F0E1.5030200@wwwdotorg.org> <51F945F9.3050906@wwwdotorg.org> In-Reply-To: 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=twosheds.infradead.org@lists.infradead.org To: Vijay Kilari Cc: "linux@arm.linux.org.uk" , "Prasun.Kapoor@caviumnetworks.com" , Will Deacon , Vijaya Kumar K , "kexec@lists.infradead.org" , "linux-arm-kernel@lists.infradead.org" On 08/01/2013 07:49 AM, Vijay Kilari wrote: > On Wed, Jul 31, 2013 at 10:44 PM, Stephen Warren wrote: >> On 07/31/2013 05:37 AM, Vijay Kilari wrote: >>> On Tue, Jul 30, 2013 at 10:29 PM, Stephen Warren wrote: >>>> On 07/30/2013 04:37 AM, Vijay Kilari wrote: >>>>> On Fri, Jul 26, 2013 at 10:38 PM, Stephen Warren wrote: >>>> ... >>>>>> Does a kernel that's used as the crash kernel guarantee: >>>>>> >>>>>> * Never to re-use the memory that was used by the previous kernel, so >>>>>> that the spin loop code/data won't be corrupted, ever, no matter how >>>>>> long the crash recovery kernel runs. >>>>>> >>>>>> * Not use SMP, so there's never a need to re-activate the non-boot CPUs, >>>>>> which might not work if they aren't truly disabled but rather just >>>>>> running a pin loop? >>>>> >>>>> From cat /proc/iomem, normal kernel is executed from (0x80xxxxxx) with crash >>>>> kernel reserved 64M@0xa0000000 >>>>> >>>>> 80000000-bfffffff : System RAM >>>>> 80008000-805aeddf : Kernel code >>>>> 805e2000-8063e427 : Kernel data >>>>> a0000000-a3ffffff : Crash kernel >>>>> >>>>> crash kernel is loaded to reserved memory location and is executed from there. >>>>> I could confirm this from /proc/iomem when crash kernel is running >>>>> >>>>> a0000000-a3efffff : System RAM >>>>> a0008000-a05aeddf : Kernel code >>>>> a05e2000-a063e427 : Kernel data >>>> >>>> OK, but in the crash dump kernel, is 80008000..8063e427 reserved as >>>> well, which would guarantee that the spin loop being executed by the >>>> non-crash CPUs won't be corrupted? >>> >>> The crash dump kernel runs from reserved memory area (0xa0000000 - 0xa3effffff). >>> So it should not corrupt the memory area of original kernel that was running >>> at 0x80000000,where other CPU's are in spin loop. >> >> What about dynamic allocations? > > IMHO, it is the kdump functionality to ensure that it won't corrupt > original kernel's dynamic allocations OK, if there are explicit measure to assure this already, then there's no issue. _______________________________________________ kexec mailing list kexec@lists.infradead.org http://lists.infradead.org/mailman/listinfo/kexec