KVM: LAPIC: Trace LAPIC timer expiration on every vmentry

In commit ec0671d5684a ("KVM: LAPIC: Delay trace_kvm_wait_lapic_expire
tracepoint to after vmexit", 2019-06-04), trace_kvm_wait_lapic_expire
was moved after guest_exit_irqoff() because invoking tracepoints within
kvm_guest_enter/kvm_guest_exit caused a lockdep splat.

These days this is not necessary, because commit 87fa7f3e98a1 ("x86/kvm:
Move context tracking where it belongs", 2020-07-09) restricted
the RCU extended quiescent state to be closer to vmentry/vmexit.
Moving the tracepoint back to __kvm_wait_lapic_expire is more accurate,
because it will be reported even if vcpu_enter_guest causes multiple
vmentries via the IPI/Timer fast paths, and it allows the removal of
advance_expire_delta.

Signed-off-by: Wanpeng Li <wanpengli@tencent.com>
Message-Id: <1650961551-38390-1-git-send-email-wanpengli@tencent.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
index 66b0eb0..a4e9eb3 100644 (file)
--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -1648,10 +1648,10 @@ static void __kvm_wait_lapic_expire(struct kvm_vcpu *vcpu)
        tsc_deadline = apic->lapic_timer.expired_tscdeadline;
        apic->lapic_timer.expired_tscdeadline = 0;
        guest_tsc = kvm_read_l1_tsc(vcpu, rdtsc());
-       apic->lapic_timer.advance_expire_delta = guest_tsc - tsc_deadline;
+       trace_kvm_wait_lapic_expire(vcpu->vcpu_id, guest_tsc - tsc_deadline);
 
        if (lapic_timer_advance_dynamic) {
-               adjust_lapic_timer_advance(vcpu, apic->lapic_timer.advance_expire_delta);
+               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

diff --git a/arch/x86/kvm/lapic.h b/arch/x86/kvm/lapic.h
index 4e4f8a2..65bb2a8 100644 (file)
--- a/arch/x86/kvm/lapic.h
+++ b/arch/x86/kvm/lapic.h
@@ -38,7 +38,6 @@ struct kvm_timer {
        u64 tscdeadline;
        u64 expired_tscdeadline;
        u32 timer_advance_ns;
-       s64 advance_expire_delta;
        atomic_t pending;                       /* accumulated triggered timers */
        bool hv_timer_in_use;
 };

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 476ea09..8b62c9b 100644 (file)
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -10310,14 +10310,6 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
         */
        guest_timing_exit_irqoff();
 
-       if (lapic_in_kernel(vcpu)) {
-               s64 delta = vcpu->arch.apic->lapic_timer.advance_expire_delta;
-               if (delta != S64_MIN) {
-                       trace_kvm_wait_lapic_expire(vcpu->vcpu_id, delta);
-                       vcpu->arch.apic->lapic_timer.advance_expire_delta = S64_MIN;
-               }
-       }
-
        local_irq_enable();
        preempt_enable();