Merging upstream version 6.10.3.

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 21 insertions, 18 deletions

diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
index ebf41023be..acd7d48100 100644
--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -59,7 +59,17 @@
 #define MAX_APIC_VECTOR			256
 #define APIC_VECTORS_PER_REG		32
 
-static bool lapic_timer_advance_dynamic __read_mostly;
+/*
+ * Enable local APIC timer advancement (tscdeadline mode only) with adaptive
+ * tuning.  When enabled, KVM programs the host timer event to fire early, i.e.
+ * before the deadline expires, to account for the delay between taking the
+ * VM-Exit (to inject the guest event) and the subsequent VM-Enter to resume
+ * the guest, i.e. so that the interrupt arrives in the guest with minimal
+ * latency relative to the deadline programmed by the guest.
+ */
+static bool lapic_timer_advance __read_mostly = true;
+module_param(lapic_timer_advance, bool, 0444);
+
 #define LAPIC_TIMER_ADVANCE_ADJUST_MIN	100	/* clock cycles */
 #define LAPIC_TIMER_ADVANCE_ADJUST_MAX	10000	/* clock cycles */
 #define LAPIC_TIMER_ADVANCE_NS_INIT	1000
@@ -1854,16 +1864,14 @@ static void __kvm_wait_lapic_expire(struct kvm_vcpu *vcpu)
 	guest_tsc = kvm_read_l1_tsc(vcpu, rdtsc());
 	trace_kvm_wait_lapic_expire(vcpu->vcpu_id, guest_tsc - tsc_deadline);
 
-	if (lapic_timer_advance_dynamic) {
-		adjust_lapic_timer_advance(vcpu, guest_tsc - tsc_deadline);
-		/*
-		 * If the timer fired early, reread the TSC to account for the
-		 * overhead of the above adjustment to avoid waiting longer
-		 * than is necessary.
-		 */
-		if (guest_tsc < tsc_deadline)
-			guest_tsc = kvm_read_l1_tsc(vcpu, rdtsc());
-	}
+	adjust_lapic_timer_advance(vcpu, guest_tsc - tsc_deadline);
+
+	/*
+	 * If the timer fired early, reread the TSC to account for the overhead
+	 * of the above adjustment to avoid waiting longer than is necessary.
+	 */
+	if (guest_tsc < tsc_deadline)
+		guest_tsc = kvm_read_l1_tsc(vcpu, rdtsc());
 
 	if (guest_tsc < tsc_deadline)
 		__wait_lapic_expire(vcpu, tsc_deadline - guest_tsc);
@@ -2812,7 +2820,7 @@ static enum hrtimer_restart apic_timer_fn(struct hrtimer *data)
 		return HRTIMER_NORESTART;
 }
 
-int kvm_create_lapic(struct kvm_vcpu *vcpu, int timer_advance_ns)
+int kvm_create_lapic(struct kvm_vcpu *vcpu)
 {
 	struct kvm_lapic *apic;
 
@@ -2845,13 +2853,8 @@ int kvm_create_lapic(struct kvm_vcpu *vcpu, int timer_advance_ns)
 	hrtimer_init(&apic->lapic_timer.timer, CLOCK_MONOTONIC,
 		     HRTIMER_MODE_ABS_HARD);
 	apic->lapic_timer.timer.function = apic_timer_fn;
-	if (timer_advance_ns == -1) {
+	if (lapic_timer_advance)
 		apic->lapic_timer.timer_advance_ns = LAPIC_TIMER_ADVANCE_NS_INIT;
-		lapic_timer_advance_dynamic = true;
-	} else {
-		apic->lapic_timer.timer_advance_ns = timer_advance_ns;
-		lapic_timer_advance_dynamic = false;
-	}
 
 	/*
 	 * Stuff the APIC ENABLE bit in lieu of temporarily incrementing