From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx1.redhat.com (mx1.redhat.com [209.132.183.28]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 61E211A2F51 for ; Thu, 5 Nov 2015 00:54:56 +1100 (AEDT) Subject: Re: [PATCH] powerpc: on crash, kexec'ed kernel needs all CPUs are online To: Hari Bathini , Benjamin Herrenschmidt , Paul Mackerras , Michael Ellerman References: <1444935658-27319-1-git-send-email-lvivier@redhat.com> <5639FB4A.7020508@linux.vnet.ibm.com> Cc: dgibson@redhat.com, thuth@redhat.com, linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org From: Laurent Vivier Message-ID: <563A0E2B.4090404@redhat.com> Date: Wed, 4 Nov 2015 14:54:51 +0100 MIME-Version: 1.0 In-Reply-To: <5639FB4A.7020508@linux.vnet.ibm.com> Content-Type: text/plain; charset=utf-8 List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On 04/11/2015 13:34, Hari Bathini wrote: > On 10/16/2015 12:30 AM, Laurent Vivier wrote: >> On kexec, all secondary offline CPUs are onlined before >> starting the new kernel, this is not done in the case of kdump. >> >> If kdump is configured and a kernel crash occurs whereas >> some secondaries CPUs are offline (SMT=off), >> the new kernel is not able to start them and displays some >> "Processor X is stuck.". >> >> Starting with POWER8, subcore logic relies on all threads of >> core being booted. So, on startup kernel tries to start all >> threads, and asks OPAL (or RTAS) to start all CPUs (including >> threads). If a CPU has been offlined by the previous kernel, >> it has not been returned to OPAL, and thus OPAL cannot restart >> it: this CPU has been lost... >> >> Signed-off-by: Laurent Vivier > > > Hi Laurent, Hi Hari, > Sorry for jumping too late into this. better late than never :) > Are you seeing this issue even with the below patches: > > pseries: > http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=c1caae3de46a072d0855729aed6e793e536a4a55 > > > opal/powernv: > https://github.com/open-power/skiboot/commit/9ee56b5 Very interesting. Is there a way to have a firmware with the fix ? Thanks, Laurent > Thanks > Hari > >> --- >> arch/powerpc/kernel/crash.c | 20 ++++++++++++++++++++ >> 1 file changed, 20 insertions(+) >> >> diff --git a/arch/powerpc/kernel/crash.c b/arch/powerpc/kernel/crash.c >> index 51dbace..3ca9452 100644 >> --- a/arch/powerpc/kernel/crash.c >> +++ b/arch/powerpc/kernel/crash.c >> @@ -19,6 +19,7 @@ >> #include >> #include >> #include >> +#include >> #include >> #include >> @@ -299,11 +300,30 @@ int crash_shutdown_unregister(crash_shutdown_t >> handler) >> } >> EXPORT_SYMBOL(crash_shutdown_unregister); >> +/* >> + * The next kernel will try to start all secondary CPUs and if >> + * there are not online it will fail to start them. >> + * >> + */ >> +static void wake_offline_cpus(void) >> +{ >> + int cpu = 0; >> + >> + for_each_present_cpu(cpu) { >> + if (!cpu_online(cpu)) { >> + pr_info("kexec: Waking offline cpu %d.\n", cpu); >> + cpu_up(cpu); >> + } >> + } >> +} >> + >> void default_machine_crash_shutdown(struct pt_regs *regs) >> { >> unsigned int i; >> int (*old_handler)(struct pt_regs *regs); >> + wake_offline_cpus(); >> + >> /* >> * This function is only called after the system >> * has panicked or is otherwise in a critical state. >