Re: [PATCH 1/2] powerpc/time: Use clockevents_register_device(), fixing an issue with large decrementer
From: Michael Ellerman <mpe@ellerman.id.au>
Date: 2018-10-14 12:42:48
Subsystem:
linux for powerpc (32-bit and 64-bit), the rest · Maintainers:
Madhavan Srinivasan, Linus Torvalds
Anton Blanchard [off-list ref] writes:
quoted hunk ↗ jump to hunk
diff --git a/arch/powerpc/kernel/time.c b/arch/powerpc/kernel/time.c index 70f145e02487..6a1f0a084ca3 100644 --- a/arch/powerpc/kernel/time.c +++ b/arch/powerpc/kernel/time.c@@ -1035,18 +1035,7 @@ static void __init set_decrementer_max(void) static void __init init_decrementer_clockevent(void) { - int cpu = smp_processor_id(); - - clockevents_calc_mult_shift(&decrementer_clockevent, ppc_tb_freq, 4); - - decrementer_clockevent.max_delta_ns = - clockevent_delta2ns(decrementer_max, &decrementer_clockevent); - decrementer_clockevent.max_delta_ticks = decrementer_max; - decrementer_clockevent.min_delta_ns = - clockevent_delta2ns(2, &decrementer_clockevent); - decrementer_clockevent.min_delta_ticks = 2; - - register_decrementer_clockevent(cpu); + register_decrementer_clockevent(smp_processor_id()); }
This broke KVM PR :) Because we no longer set the mult/shift in decrementer_clockevent, which is used in kvmppc_emulate_dec(). The patch below fixes it, though it'd be nice to come up with something cleaner eventually. cheers
diff --git a/arch/powerpc/kernel/time.c b/arch/powerpc/kernel/time.c
index 6a1f0a084ca3..d21b2b88c0a7 100644
--- a/arch/powerpc/kernel/time.c
+++ b/arch/powerpc/kernel/time.c@@ -1036,6 +1036,9 @@ static void __init set_decrementer_max(void) static void __init init_decrementer_clockevent(void) { register_decrementer_clockevent(smp_processor_id()); + + /* Set values for KVM, see kvm_emulate_dec() */ + decrementer_clockevent = *dec; } void secondary_cpu_time_init(void)