kvm: x86: only channel 0 of the i8254 is linked to the HPET

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>

2 files changed, 3 insertions, 1 deletions

diff --git a/arch/x86/kvm/i8254.c b/arch/x86/kvm/i8254.c
index 08116ff227cc..b0ea42b78ccd 100644
--- a/arch/x86/kvm/i8254.c
+++ b/arch/x86/kvm/i8254.c
@@ -420,6 +420,7 @@ void kvm_pit_load_count(struct kvm *kvm, int channel, u32 val, int hpet_legacy_s
         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);
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 7ffc224bbe41..97592e190413 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -3606,7 +3606,8 @@ static int kvm_vm_ioctl_set_pit2(struct kvm *kvm, struct kvm_pit_state2 *ps)
                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 0;
 }