KVM: PIT: support mode 3

The in-kernel PIT emulation ignores pending timers if operating
under mode 3, which for example Hurd uses.

This mode should output a square wave, high for (N+1)/2 counts and low
for (N-1)/2 counts. As we only care about the resulting interrupts, the
period is N, and mode 3 is the same as mode 2 with regard to
interrupts.

Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>
Signed-off-by: Avi Kivity <avi@qumranet.com>

1 files changed, 1 insertions, 0 deletions

diff --git a/arch/x86/kvm/i8254.c b/arch/x86/kvm/i8254.c
index 735ec9a0b360..60074dc66bd7 100644
--- a/arch/x86/kvm/i8254.c
+++ b/arch/x86/kvm/i8254.c
@@ -308,6 +308,7 @@ static void pit_load_count(struct kvm *kvm, int channel, u32 val)
                 create_pit_timer(&ps->pit_timer, val, 0);
                 break;
         case 2:
+        case 3:
                 create_pit_timer(&ps->pit_timer, val, 1);
                 break;
         default: