Commit 205df4d1 authored by Jan Kiszka's avatar Jan Kiszka Committed by Marcelo Tosatti
Browse files

kvm: i8254: Cache kernel clock offset in KVMPITState 



To prepare the final fix for clock calibration issues with the in-kernel
PIT, we want to cache the offset between vmclock and the clock used by
the in-kernel PIT. So far, we only need to update it when the VM state
changes between running and stopped because we only read the in-kernel
PIT state while the VM is running.

Signed-off-by: default avatarJan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: default avatarMarcelo Tosatti <mtosatti@redhat.com>
parent 873359d4

hw/kvm/i8254.c

+24 −14
Original line number Diff line number Diff line
@@ -35,7 +35,8 @@ 
typedef struct KVMPITState {

    PITCommonState pit;

    LostTickPolicy lost_tick_policy;

    bool state_valid;

    bool vm_stopped;

    int64_t kernel_clock_offset;

} KVMPITState;



static int64_t abs64(int64_t v)
@@ -43,19 +44,11 @@ static int64_t abs64(int64_t v) 
    return v < 0 ? -v : v;

}



static void kvm_pit_get(PITCommonState *pit)

static void kvm_pit_update_clock_offset(KVMPITState *s)

{

    KVMPITState *s = DO_UPCAST(KVMPITState, pit, pit);

    struct kvm_pit_state2 kpit;

    struct kvm_pit_channel_state *kchan;

    struct PITChannelState *sc;

    int64_t offset, clock_offset;

    struct timespec ts;

    int i, ret;



    if (s->state_valid) {

        return;

    }

    int i;



    /*

     * Measure the delta between CLOCK_MONOTONIC, the base used for
@@ -72,6 +65,21 @@ static void kvm_pit_get(PITCommonState *pit) 
            clock_offset = offset;

        }

    }

    s->kernel_clock_offset = clock_offset;

}



static void kvm_pit_get(PITCommonState *pit)

{

    KVMPITState *s = DO_UPCAST(KVMPITState, pit, pit);

    struct kvm_pit_state2 kpit;

    struct kvm_pit_channel_state *kchan;

    struct PITChannelState *sc;

    int i, ret;



    /* No need to re-read the state if VM is stopped. */

    if (s->vm_stopped) {

        return;

    }



    if (kvm_has_pit_state2()) {

        ret = kvm_vm_ioctl(kvm_state, KVM_GET_PIT2, &kpit);
@@ -106,7 +114,7 @@ static void kvm_pit_get(PITCommonState *pit) 
        sc->mode = kchan->mode;

        sc->bcd = kchan->bcd;

        sc->gate = kchan->gate;

        sc->count_load_time = kchan->count_load_time + clock_offset;

        sc->count_load_time = kchan->count_load_time + s->kernel_clock_offset;

    }



    sc = &pit->channels[0];
@@ -211,10 +219,12 @@ static void kvm_pit_vm_state_change(void *opaque, int running, 
    KVMPITState *s = opaque;



    if (running) {

        s->state_valid = false;

        kvm_pit_update_clock_offset(s);

        s->vm_stopped = false;

    } else {

        kvm_pit_update_clock_offset(s);

        kvm_pit_get(&s->pit);

        s->state_valid = true;

        s->vm_stopped = true;

    }

}