[PATCH 3.2 44/70] kvm: x86: only channel 0 of the i8254 is linked to the HPET

Ben Hutchings
2016-01-18T03:35:09Z

From: Paolo Bonzini <pbonzini@redhat.com>

commit e5e57e7a03b1cdcb98e4aed135def2a08cbf3257 upstream.

While setting the KVM PIT counters in 'kvm_pit_load_count', if
'hpet_legacy_start' is set, the function disables the timer on
channel[0], instead of the respective index 'channel'. This is
because channels 1-3 are not linked to the HPET. Fix the caller
to only activate the special HPET processing for channel 0.

Reported-by: P J P <pjp@fedoraproject.org>
Fixes: 0185604c2d82c560dab2f2933a18f797e74ab5a8
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
arch/x86/kvm/i8254.c | 1 +
arch/x86/kvm/x86.c | 3 ++-
2 files changed, 3 insertions(+), 1 deletion(-)

--- a/arch/x86/kvm/i8254.c
+++ b/arch/x86/kvm/i8254.c
@@ -437,6 +437,7 @@ void kvm_pit_load_count(struct kvm *kvm,
u8 saved_mode;
if (hpet_legacy_start) {
/* save existing mode for later reenablement */
+ WARN_ON(channel != 0);
saved_mode = kvm->arch.vpit->pit_state.channels[0].mode;
kvm->arch.vpit->pit_state.channels[0].mode = 0xff; /* disable timer */
pit_load_count(kvm, channel, val);
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -3470,7 +3470,8 @@ static int kvm_vm_ioctl_set_pit2(struct
sizeof(kvm->arch.vpit->pit_state.channels));
kvm->arch.vpit->pit_state.flags = ps->flags;
for (i = 0; i < 3; i++)
- kvm_pit_load_count(kvm, i, kvm->arch.vpit->pit_state.channels[i].count, start);
+ kvm_pit_load_count(kvm, i, kvm->arch.vpit->pit_state.channels[i].count,
+ start && i == 0);
mutex_unlock(&kvm->arch.vpit->pit_state.lock);
return r;
}