On 20.09.2024 10:35, Roger Pau Monné wrote: > On Thu, Sep 19, 2024 at 10:19:49PM +0200, Andrew Cooper wrote: >> On 19/09/2024 4:27 pm, Roger Pau Monne wrote: >>> @@ -364,6 +369,18 @@ void smp_send_stop(void) >>> fixup_irqs(cpumask_of(cpu), 0); >>> local_irq_enable(); >>> >>> + /* >>> + * Mask the local APIC error vector ahead of stopping CPUs. >>> + * >>> + * On AMD the local APIC will report Receive Accept Errors if the >>> + * destination APIC ID of an interrupt message is not online. >>> There's >>> + * no guarantee that fixup_irqs() will evacuate all interrupts - >>> + * possibly because the sole CPU remaining online doesn't have >>> enough >>> + * vectors to accommodate all. >>> + */ >>> + smp_call_function(mask_lvterr, NULL, true); >>> + mask_lvterr(NULL); >>> + >>> smp_call_function(stop_this_cpu, NULL, 0); >> >> Irrespective of the question over approach, stop_this_cpu() should end >> up clearing LVTERR. Why doesn't that suffice? > > No, because those are no ordered. The sequence needs to strictly be: > > - Mask LVTERR on all CPUs. > <wait for masking to be done uniformly> > - Stop CPUs. > > Otherwise CPUs might be stopped before LVTERR has been uniformly > masked, leading to Receive accept error reported on the CPUs that > don't yet have LVTERR masked.
Yet fixup_irqs() has moved everything to CPU0. Nothing should go to any of the APs anymore. Fiddling with LVTERR here feels like curing a symptom rather than the root cause. Jan
