On Fri, Dec 04, 2015 at 07:29:36PM -0500, Ashok Raj wrote: > Linux has logical cpu offline capability. That can be triggered by: > > # echo 0 > /sys/devices/system/cpu/cpuX/online > > In Intel Architecture, MCE's are broadcasted to all CPUs in the system. > > This includes the CPUs marked offline by Linux. Unless the CPU's were removed > via an ACPI notification, in which case the cpu's are removed from the > cpu_present_map. > > This patch ensures offline CPU's don't participate in MCE rendezvous, but > simply perform clearing some status bits to ensure a second MCE wont cause > automatic shutdown. > > Without the patch, mce_start will increment mce_callin, but mce_start would > only wait for all online_cpus. So offline cpu's should avoid participating > in the rendezvous process. > > Reviewed-by: Tony Luck <[email protected]> > Cc: [email protected] > Signed-off-by: Ashok Raj <[email protected]> > --- > arch/x86/kernel/cpu/mcheck/mce.c | 13 +++++++++++++ > 1 file changed, 13 insertions(+)
Tested on a box here, massaged commit message and queued for 4.4, thanks. --- From: Ashok Raj <[email protected]> Date: Thu, 3 Dec 2015 19:16:10 -0500 Subject: [PATCH] x86/mce: Ensure offline CPUs don't participate in rendezvous process Intel's MCA implementation broadcasts MCEs to all CPUs on the node. This poses a problem for offlined CPUs which cannot participate in the rendezvous process: Kernel panic - not syncing: Timeout: Not all CPUs entered broadcast exception handler Kernel Offset: disabled Rebooting in 100 seconds.. More specifically, Linux does a soft offline of a CPU when writing a 0 to /sys/devices/system/cpu/cpuX/online, which doesn't prevent the #MC exception from being broadcasted to that CPU. Ensure that offline CPUs don't participate in the MCE rendezvous and clear the RIP valid status bit so that a second MCE won't cause a shutdown. Without the patch, mce_start() will increment mce_callin and wait for all CPUs. Offlined CPUs should avoid participating in the rendezvous process altogether. Reviewed-by: Tony Luck <[email protected]> Signed-off-by: Ashok Raj <[email protected]> Cc: "H. Peter Anvin" <[email protected]> Cc: Ingo Molnar <[email protected]> Cc: linux-edac <[email protected]> Cc: [email protected] Cc: Thomas Gleixner <[email protected]> Cc: x86-ml <[email protected]> Link: http://lkml.kernel.org/r/[email protected] [ Massage commit message. ] Signed-off-by: Borislav Petkov <[email protected]> --- arch/x86/kernel/cpu/mcheck/mce.c | 11 +++++++++++ 1 file changed, 11 insertions(+) diff --git a/arch/x86/kernel/cpu/mcheck/mce.c b/arch/x86/kernel/cpu/mcheck/mce.c index 3865e95cc5ec..a006f4cd792b 100644 --- a/arch/x86/kernel/cpu/mcheck/mce.c +++ b/arch/x86/kernel/cpu/mcheck/mce.c @@ -1002,6 +1002,17 @@ void do_machine_check(struct pt_regs *regs, long error_code) int flags = MF_ACTION_REQUIRED; int lmce = 0; + /* If this CPU is offline, just bail out. */ + if (cpu_is_offline(smp_processor_id())) { + u64 mcgstatus; + + mcgstatus = mce_rdmsrl(MSR_IA32_MCG_STATUS); + if (mcgstatus & MCG_STATUS_RIPV) { + mce_wrmsrl(MSR_IA32_MCG_STATUS, 0); + return; + } + } + ist_enter(regs); this_cpu_inc(mce_exception_count); -- 2.3.5 -- Regards/Gruss, Boris. ECO tip #101: Trim your mails when you reply. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
