On Fri, Nov 08, 2024 at 08:49:31AM -0500, Len Brown wrote:
diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c index 766f092dab80..910cb2d72c13 100644 --- a/arch/x86/kernel/smpboot.c +++ b/arch/x86/kernel/smpboot.c @@ -1377,6 +1377,9 @@ void smp_kick_mwait_play_dead(void) for (i = 0; READ_ONCE(md->status) != newstate && i < 1000; i++) { /* Bring it out of mwait */ WRITE_ONCE(md->control, newstate);
/* If MONITOR unreliable, send IPI */if (boot_cpu_has_bug(X86_BUG_MONITOR))__apic_send_IPI(cpu, RESCHEDULE_VECTOR); udelay(5);
Going over that code again, mwait_play_dead() is doing __mwait(.exc=0) with IRQs disabled.
So that IPI you're trying to send there won't do no nothing :-/
Now that comment there says MCE/NMI/SMI are still open (non-maskable etc.) so perhaps prod it on the NMI vector?
This does seem to suggest the above code path wasn't actually tested. Perhaps mark your local machine with BUG_MONITOR, remove the md->control WRITE_ONCE() and try kexec to test it?
Thomas, any other thoughts?