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KVM: lapic: Track lapic timer advance per vCPU
Automatically adjusting the globally-shared timer advancement could
corrupt the timer, e.g. if multiple vCPUs are concurrently adjusting
the advancement value. That could be partially fixed by using a local
variable for the arithmetic, but it would still be susceptible to a
race when setting timer_advance_adjust_done.
And because virtual_tsc_khz and tsc_scaling_ratio are per-vCPU, the
correct calibration for a given vCPU may not apply to all vCPUs.
Furthermore, lapic_timer_advance_ns is marked __read_mostly, which is
effectively violated when finding a stable advancement takes an extended
amount of timer.
Opportunistically change the definition of lapic_timer_advance_ns to
a u32 so that it matches the style of struct kvm_timer. Explicitly
pass the param to kvm_create_lapic() so that it doesn't have to be
exposed to lapic.c, thus reducing the probability of unintentionally
using the global value instead of the per-vCPU value.
Cc: Liran Alon <liran.alon@oracle.com>
Cc: Wanpeng Li <wanpengli@tencent.com>
Reviewed-by: Liran Alon <liran.alon@oracle.com>
Cc: stable@vger.kernel.org
Fixes: 3b8a5df6c4
("KVM: LAPIC: Tune lapic_timer_advance_ns automatically")
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
parent
57bf67e73c
commit
39497d7660
5 changed files with 28 additions and 25 deletions
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@ -70,7 +70,6 @@
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#define APIC_BROADCAST 0xFF
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#define X2APIC_BROADCAST 0xFFFFFFFFul
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static bool lapic_timer_advance_adjust_done = false;
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#define LAPIC_TIMER_ADVANCE_ADJUST_DONE 100
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/* step-by-step approximation to mitigate fluctuation */
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#define LAPIC_TIMER_ADVANCE_ADJUST_STEP 8
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@ -1485,6 +1484,7 @@ static bool lapic_timer_int_injected(struct kvm_vcpu *vcpu)
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void wait_lapic_expire(struct kvm_vcpu *vcpu)
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{
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struct kvm_lapic *apic = vcpu->arch.apic;
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u32 timer_advance_ns = apic->lapic_timer.timer_advance_ns;
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u64 guest_tsc, tsc_deadline, ns;
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if (!lapic_in_kernel(vcpu))
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@ -1504,34 +1504,36 @@ void wait_lapic_expire(struct kvm_vcpu *vcpu)
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/* __delay is delay_tsc whenever the hardware has TSC, thus always. */
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if (guest_tsc < tsc_deadline)
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__delay(min(tsc_deadline - guest_tsc,
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nsec_to_cycles(vcpu, lapic_timer_advance_ns)));
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nsec_to_cycles(vcpu, timer_advance_ns)));
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if (!lapic_timer_advance_adjust_done) {
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if (!apic->lapic_timer.timer_advance_adjust_done) {
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/* too early */
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if (guest_tsc < tsc_deadline) {
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ns = (tsc_deadline - guest_tsc) * 1000000ULL;
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do_div(ns, vcpu->arch.virtual_tsc_khz);
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lapic_timer_advance_ns -= min((unsigned int)ns,
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lapic_timer_advance_ns / LAPIC_TIMER_ADVANCE_ADJUST_STEP);
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timer_advance_ns -= min((u32)ns,
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timer_advance_ns / LAPIC_TIMER_ADVANCE_ADJUST_STEP);
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} else {
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/* too late */
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ns = (guest_tsc - tsc_deadline) * 1000000ULL;
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do_div(ns, vcpu->arch.virtual_tsc_khz);
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lapic_timer_advance_ns += min((unsigned int)ns,
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lapic_timer_advance_ns / LAPIC_TIMER_ADVANCE_ADJUST_STEP);
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timer_advance_ns += min((u32)ns,
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timer_advance_ns / LAPIC_TIMER_ADVANCE_ADJUST_STEP);
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}
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if (abs(guest_tsc - tsc_deadline) < LAPIC_TIMER_ADVANCE_ADJUST_DONE)
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lapic_timer_advance_adjust_done = true;
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if (unlikely(lapic_timer_advance_ns > 5000)) {
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lapic_timer_advance_ns = 0;
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lapic_timer_advance_adjust_done = true;
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apic->lapic_timer.timer_advance_adjust_done = true;
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if (unlikely(timer_advance_ns > 5000)) {
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timer_advance_ns = 0;
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apic->lapic_timer.timer_advance_adjust_done = true;
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}
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apic->lapic_timer.timer_advance_ns = timer_advance_ns;
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}
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}
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static void start_sw_tscdeadline(struct kvm_lapic *apic)
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{
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u64 guest_tsc, tscdeadline = apic->lapic_timer.tscdeadline;
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struct kvm_timer *ktimer = &apic->lapic_timer;
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u64 guest_tsc, tscdeadline = ktimer->tscdeadline;
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u64 ns = 0;
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ktime_t expire;
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struct kvm_vcpu *vcpu = apic->vcpu;
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@ -1551,11 +1553,10 @@ static void start_sw_tscdeadline(struct kvm_lapic *apic)
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do_div(ns, this_tsc_khz);
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if (likely(tscdeadline > guest_tsc) &&
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likely(ns > lapic_timer_advance_ns)) {
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likely(ns > apic->lapic_timer.timer_advance_ns)) {
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expire = ktime_add_ns(now, ns);
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expire = ktime_sub_ns(expire, lapic_timer_advance_ns);
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hrtimer_start(&apic->lapic_timer.timer,
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expire, HRTIMER_MODE_ABS_PINNED);
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expire = ktime_sub_ns(expire, ktimer->timer_advance_ns);
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hrtimer_start(&ktimer->timer, expire, HRTIMER_MODE_ABS_PINNED);
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} else
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apic_timer_expired(apic);
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@ -2262,7 +2263,7 @@ static enum hrtimer_restart apic_timer_fn(struct hrtimer *data)
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return HRTIMER_NORESTART;
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}
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int kvm_create_lapic(struct kvm_vcpu *vcpu)
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int kvm_create_lapic(struct kvm_vcpu *vcpu, u32 timer_advance_ns)
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{
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struct kvm_lapic *apic;
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@ -2286,6 +2287,7 @@ int kvm_create_lapic(struct kvm_vcpu *vcpu)
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hrtimer_init(&apic->lapic_timer.timer, CLOCK_MONOTONIC,
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HRTIMER_MODE_ABS_PINNED);
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apic->lapic_timer.timer.function = apic_timer_fn;
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apic->lapic_timer.timer_advance_ns = timer_advance_ns;
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/*
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* APIC is created enabled. This will prevent kvm_lapic_set_base from
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@ -31,8 +31,10 @@ struct kvm_timer {
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u32 timer_mode_mask;
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u64 tscdeadline;
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u64 expired_tscdeadline;
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u32 timer_advance_ns;
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atomic_t pending; /* accumulated triggered timers */
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bool hv_timer_in_use;
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bool timer_advance_adjust_done;
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};
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struct kvm_lapic {
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@ -62,7 +64,7 @@ struct kvm_lapic {
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struct dest_map;
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int kvm_create_lapic(struct kvm_vcpu *vcpu);
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int kvm_create_lapic(struct kvm_vcpu *vcpu, u32 timer_advance_ns);
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void kvm_free_lapic(struct kvm_vcpu *vcpu);
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int kvm_apic_has_interrupt(struct kvm_vcpu *vcpu);
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@ -7032,6 +7032,7 @@ static int vmx_set_hv_timer(struct kvm_vcpu *vcpu, u64 guest_deadline_tsc)
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{
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struct vcpu_vmx *vmx;
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u64 tscl, guest_tscl, delta_tsc, lapic_timer_advance_cycles;
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struct kvm_timer *ktimer = &vcpu->arch.apic->lapic_timer;
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if (kvm_mwait_in_guest(vcpu->kvm))
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return -EOPNOTSUPP;
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@ -7040,7 +7041,8 @@ static int vmx_set_hv_timer(struct kvm_vcpu *vcpu, u64 guest_deadline_tsc)
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tscl = rdtsc();
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guest_tscl = kvm_read_l1_tsc(vcpu, tscl);
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delta_tsc = max(guest_deadline_tsc, guest_tscl) - guest_tscl;
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lapic_timer_advance_cycles = nsec_to_cycles(vcpu, lapic_timer_advance_ns);
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lapic_timer_advance_cycles = nsec_to_cycles(vcpu,
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ktimer->timer_advance_ns);
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if (delta_tsc > lapic_timer_advance_cycles)
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delta_tsc -= lapic_timer_advance_cycles;
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@ -137,9 +137,8 @@ static u32 __read_mostly tsc_tolerance_ppm = 250;
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module_param(tsc_tolerance_ppm, uint, S_IRUGO | S_IWUSR);
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/* lapic timer advance (tscdeadline mode only) in nanoseconds */
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unsigned int __read_mostly lapic_timer_advance_ns = 1000;
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static u32 __read_mostly lapic_timer_advance_ns = 1000;
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module_param(lapic_timer_advance_ns, uint, S_IRUGO | S_IWUSR);
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EXPORT_SYMBOL_GPL(lapic_timer_advance_ns);
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static bool __read_mostly vector_hashing = true;
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module_param(vector_hashing, bool, S_IRUGO);
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@ -7873,7 +7872,7 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
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}
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trace_kvm_entry(vcpu->vcpu_id);
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if (lapic_timer_advance_ns)
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if (vcpu->arch.apic->lapic_timer.timer_advance_ns)
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wait_lapic_expire(vcpu);
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guest_enter_irqoff();
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if (irqchip_in_kernel(vcpu->kvm)) {
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vcpu->arch.apicv_active = kvm_x86_ops->get_enable_apicv(vcpu);
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r = kvm_create_lapic(vcpu);
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r = kvm_create_lapic(vcpu, lapic_timer_advance_ns);
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if (r < 0)
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goto fail_mmu_destroy;
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} else
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@ -294,8 +294,6 @@ extern u64 kvm_supported_xcr0(void);
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extern unsigned int min_timer_period_us;
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extern unsigned int lapic_timer_advance_ns;
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extern bool enable_vmware_backdoor;
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extern struct static_key kvm_no_apic_vcpu;
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