| Date | Wed, 27 Sep 2023 19:17:13 +0200 | From | Borislav Petkov <> | Subject | Re: [patch V3 25/30] x86/microcode: Rendezvous and load in NMI |
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On Tue, Sep 12, 2023 at 09:58:23AM +0200, Thomas Gleixner wrote: > From: Thomas Gleixner <tglx@linutronix.de> > > stop_machine() does not prevent the spin-waiting sibling from handling an > NMI, which is obviously violating the whole concept of rendezvous. > > Implement a static branch right in the beginning of the NMI handler which > is NOOPed except when enabled by the late loading mechanism. > > The later loader enables the static branch before stop_machine() is
s/later/late/
> invoked. Each CPU has an nmi_enable in its control structure which > indicates whether the CPU should go into the update routine. > > This is required to bridge the gap between enabling the branch and actually > being at the point where it makes sense.
Huh? "where it makes sense"?
> -static int ucode_load_cpus_stopped(void *unused) > +static bool microcode_update_handler(void) > { > unsigned int cpu = smp_processor_id(); > > @@ -430,7 +436,29 @@ static int ucode_load_cpus_stopped(void > else > ucode_load_secondary(cpu); > > - /* No point to wait here. The CPUs will all wait in stop_machine(). */ > + touch_nmi_watchdog();
AFAICT, you're touching the NMI watchdog even in the !use_nmi case.
> + return true; > +}
-- Regards/Gruss, Boris.
https://people.kernel.org/tglx/notes-about-netiquette
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