On Fri, Dec 04, 2015 at 06:57:31PM -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 | 15 ++++++++++++++-
> 1 file changed, 14 insertions(+), 1 deletion(-)
>
> diff --git a/arch/x86/kernel/cpu/mcheck/mce.c
> b/arch/x86/kernel/cpu/mcheck/mce.c
> index c5b0d56..72ea044 100644
> --- a/arch/x86/kernel/cpu/mcheck/mce.c
> +++ b/arch/x86/kernel/cpu/mcheck/mce.c
> @@ -998,7 +998,20 @@ void do_machine_check(struct pt_regs *regs, long
> error_code)
> u64 recover_paddr = ~0ull;
> int flags = MF_ACTION_REQUIRED;
> int lmce = 0;
> + unsigned int cpu = smp_processor_id();
>
> + /*
> + * if this cpu is offline, just bail out.
> + */
> + if (cpu_is_offline(cpu)) {
> + 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);
> @@ -1142,8 +1155,8 @@ void do_machine_check(struct pt_regs *regs, long
> error_code)
>
> if (worst > 0)
> mce_report_event(regs);
> - mce_wrmsrl(MSR_IA32_MCG_STATUS, 0);
> out:
> + mce_wrmsrl(MSR_IA32_MCG_STATUS, 0);
> sync_core();
>
> if (recover_paddr == ~0ull)
> --
With that hunk here you want to clear MSR_IA32_MCG_STATUS in the
!cfg->banks case, right?
If so, this should be a separate patch. Also, CC: stable with an
explanation why.
Thanks.
--
Regards/Gruss,
Boris.
SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton, HRB 21284
(AG Nürnberg)
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