On Thu, 11 Oct 2018 at 06:59, Peter Shier <pshier@xxxxxxxxxx> wrote:
>
> kvm_vcpu_ioctl_get_lapic (implements KVM_GET_LAPIC ioctl) does a bulk copy
> of the LAPIC registers but must take into account that the one-shot and
> periodic timer current count register is computed upon reads and is not
> present in register state. When restoring LAPIC state (e.g. after
> migration), restart timers from their their current count values at time of
> save.
>
> Note: When a one-shot timer expires, the code in arch/x86/kvm/lapic.c does
> not zero the value of the LAPIC initial count register (emulating HW
> behavior). If no other timer is run and pending prior to a subsequent
> KVM_GET_LAPIC call, the returned register set will include the expired
> one-shot initial count. On a subsequent KVM_SET_LAPIC call the code will
> see a non-zero initial count and start a new one-shot timer using the
> expired timer's count. This is a prior existing bug and will be addressed
> in a separate patch. Thanks to jmattson@xxxxxxxxxx for this find.
>
> Signed-off-by: Peter Shier <pshier@xxxxxxxxxx>
> Reviewed-by: Jim Mattson <jmattson@xxxxxxxxxx>
Reviewed-by: Wanpeng Li <wanpengli@xxxxxxxxxxx>
> ---
> arch/x86/kvm/lapic.c | 64 +++++++++++++++++++++++++++++++++++---------
> arch/x86/kvm/lapic.h | 7 ++++-
> 2 files changed, 58 insertions(+), 13 deletions(-)
>
> diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
> index fbb0e6df121b2..8e7f3cf552871 100644
> --- a/arch/x86/kvm/lapic.c
> +++ b/arch/x86/kvm/lapic.c
> @@ -1524,13 +1524,18 @@ static void start_sw_tscdeadline(struct kvm_lapic *apic)
> local_irq_restore(flags);
> }
>
> +static inline u64 tmict_to_ns(struct kvm_lapic *apic, u32 tmict)
> +{
> + return (u64)tmict * APIC_BUS_CYCLE_NS * (u64)apic->divide_count;
> +}
> +
> static void update_target_expiration(struct kvm_lapic *apic, uint32_t old_divisor)
> {
> ktime_t now, remaining;
> u64 ns_remaining_old, ns_remaining_new;
>
> - apic->lapic_timer.period = (u64)kvm_lapic_get_reg(apic, APIC_TMICT)
> - * APIC_BUS_CYCLE_NS * apic->divide_count;
> + apic->lapic_timer.period =
> + tmict_to_ns(apic, kvm_lapic_get_reg(apic, APIC_TMICT));
> limit_periodic_timer_frequency(apic);
>
> now = ktime_get();
> @@ -1548,14 +1553,15 @@ static void update_target_expiration(struct kvm_lapic *apic, uint32_t old_diviso
> apic->lapic_timer.target_expiration = ktime_add_ns(now, ns_remaining_new);
> }
>
> -static bool set_target_expiration(struct kvm_lapic *apic)
> +static bool set_target_expiration(struct kvm_lapic *apic, u32 count_reg)
> {
> ktime_t now;
> u64 tscl = rdtsc();
> + s64 deadline;
>
> now = ktime_get();
> - apic->lapic_timer.period = (u64)kvm_lapic_get_reg(apic, APIC_TMICT)
> - * APIC_BUS_CYCLE_NS * apic->divide_count;
> + apic->lapic_timer.period =
> + tmict_to_ns(apic, kvm_lapic_get_reg(apic, APIC_TMICT));
>
> if (!apic->lapic_timer.period) {
> apic->lapic_timer.tscdeadline = 0;
> @@ -1563,6 +1569,28 @@ static bool set_target_expiration(struct kvm_lapic *apic)
> }
>
> limit_periodic_timer_frequency(apic);
> + deadline = apic->lapic_timer.period;
> +
> + if (apic_lvtt_period(apic) || apic_lvtt_oneshot(apic)) {
> + if (unlikely(count_reg != APIC_TMICT)) {
> + deadline = tmict_to_ns(apic,
> + kvm_lapic_get_reg(apic, count_reg));
> + if (unlikely(deadline <= 0))
> + deadline = apic->lapic_timer.period;
> + else if (unlikely(deadline > apic->lapic_timer.period)) {
> + pr_info_ratelimited(
> + "kvm: vcpu %i: requested lapic timer restore with "
> + "starting count register %#x=%u (%lld ns) > initial count (%lld ns). "
> + "Using initial count to start timer.\n",
> + apic->vcpu->vcpu_id,
> + count_reg,
> + kvm_lapic_get_reg(apic, count_reg),
> + deadline, apic->lapic_timer.period);
> + kvm_lapic_set_reg(apic, count_reg, 0);
> + deadline = apic->lapic_timer.period;
> + }
> + }
> + }
>
> apic_debug("%s: bus cycle is %" PRId64 "ns, now 0x%016"
> PRIx64 ", "
> @@ -1571,12 +1599,11 @@ static bool set_target_expiration(struct kvm_lapic *apic)
> APIC_BUS_CYCLE_NS, ktime_to_ns(now),
> kvm_lapic_get_reg(apic, APIC_TMICT),
> apic->lapic_timer.period,
> - ktime_to_ns(ktime_add_ns(now,
> - apic->lapic_timer.period)));
> + ktime_to_ns(ktime_add_ns(now, deadline)));
>
> apic->lapic_timer.tscdeadline = kvm_read_l1_tsc(apic->vcpu, tscl) +
> - nsec_to_cycles(apic->vcpu, apic->lapic_timer.period);
> - apic->lapic_timer.target_expiration = ktime_add_ns(now, apic->lapic_timer.period);
> + nsec_to_cycles(apic->vcpu, deadline);
> + apic->lapic_timer.target_expiration = ktime_add_ns(now, deadline);
>
> return true;
> }
> @@ -1748,17 +1775,22 @@ void kvm_lapic_restart_hv_timer(struct kvm_vcpu *vcpu)
> restart_apic_timer(apic);
> }
>
> -static void start_apic_timer(struct kvm_lapic *apic)
> +static void __start_apic_timer(struct kvm_lapic *apic, u32 count_reg)
> {
> atomic_set(&apic->lapic_timer.pending, 0);
>
> if ((apic_lvtt_period(apic) || apic_lvtt_oneshot(apic))
> - && !set_target_expiration(apic))
> + && !set_target_expiration(apic, count_reg))
> return;
>
> restart_apic_timer(apic);
> }
>
> +static void start_apic_timer(struct kvm_lapic *apic)
> +{
> + __start_apic_timer(apic, APIC_TMICT);
> +}
> +
> static void apic_manage_nmi_watchdog(struct kvm_lapic *apic, u32 lvt0_val)
> {
> bool lvt0_in_nmi_mode = apic_lvt_nmi_mode(lvt0_val);
> @@ -2370,6 +2402,14 @@ static int kvm_apic_state_fixup(struct kvm_vcpu *vcpu,
> int kvm_apic_get_state(struct kvm_vcpu *vcpu, struct kvm_lapic_state *s)
> {
> memcpy(s->regs, vcpu->arch.apic->regs, sizeof(*s));
> +
> + /*
> + * Get calculated timer current count for remaining timer period (if
> + * any) and store it in the returned register set.
> + */
> + __kvm_lapic_set_reg(s->regs, APIC_TMCCT,
> + __apic_read(vcpu->arch.apic, APIC_TMCCT));
> +
> return kvm_apic_state_fixup(vcpu, s, false);
> }
>
> @@ -2396,7 +2436,7 @@ int kvm_apic_set_state(struct kvm_vcpu *vcpu, struct kvm_lapic_state *s)
> apic_update_lvtt(apic);
> apic_manage_nmi_watchdog(apic, kvm_lapic_get_reg(apic, APIC_LVT0));
> update_divide_count(apic);
> - start_apic_timer(apic);
> + __start_apic_timer(apic, APIC_TMCCT);
> apic->irr_pending = true;
> apic->isr_count = vcpu->arch.apicv_active ?
> 1 : count_vectors(apic->regs + APIC_ISR);
> diff --git a/arch/x86/kvm/lapic.h b/arch/x86/kvm/lapic.h
> index ed0ed39abd369..fadefa1a9d678 100644
> --- a/arch/x86/kvm/lapic.h
> +++ b/arch/x86/kvm/lapic.h
> @@ -147,9 +147,14 @@ static inline u32 kvm_lapic_get_reg(struct kvm_lapic *apic, int reg_off)
> return *((u32 *) (apic->regs + reg_off));
> }
>
> +static inline void __kvm_lapic_set_reg(char *regs, int reg_off, u32 val)
> +{
> + *((u32 *) (regs + reg_off)) = val;
> +}
> +
> static inline void kvm_lapic_set_reg(struct kvm_lapic *apic, int reg_off, u32 val)
> {
> - *((u32 *) (apic->regs + reg_off)) = val;
> + __kvm_lapic_set_reg(apic->regs, reg_off, val);
> }
>
> extern struct static_key kvm_no_apic_vcpu;
> --
> 2.19.0.605.g01d371f741-goog
>
