Commit e2a37708 authored Oct 17, 2018 by Michael Ellerman Committed by Greg Kroah-Hartman Nov 24, 2019

powerpc/time: Fix clockevent_decrementer initalisation for PR KVM



[ Upstream commit b4d16ab58c41ff0125822464bdff074cebd0fe47 ]

In the recent commit 8b78fdb045de ("powerpc/time: Use
clockevents_register_device(), fixing an issue with large
decrementer") we changed the way we initialise the decrementer
clockevent(s).

We no longer initialise the mult & shift values of
decrementer_clockevent itself.

This has the effect of breaking PR KVM, because it uses those values
in kvmppc_emulate_dec(). The symptom is guest kernels spin forever
mid-way through boot.

For now fix it by assigning back to decrementer_clockevent the mult
and shift values.

Fixes: 8b78fdb045de ("powerpc/time: Use clockevents_register_device(), fixing an issue with large decrementer")
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Sasha Levin <sashal@kernel.org>

parent ff36ace6

arch/powerpc/kernel/time.c

+4 −0

Original line number	Diff line number	Diff line
		@@ -988,6 +988,10 @@ static void register_decrementer_clockevent(int cpu)

		printk_once(KERN_DEBUG "clockevent: %s mult[%x] shift[%d] cpu[%d]\n",
		dec->name, dec->mult, dec->shift, cpu);

		/* Set values for KVM, see kvm_emulate_dec() */
		decrementer_clockevent.mult = dec->mult;
		decrementer_clockevent.shift = dec->shift;
		}

		static void enable_large_decrementer(void)