KVM: LAPIC: Delay trace_kvm_wait_lapic_expire tracepoint to after vmexit

wait_lapic_expire() call was moved above guest_enter_irqoff() because of
its tracepoint, which violated the RCU extended quiescent state invoked
by guest_enter_irqoff()[1][2]. This patch simply moves the tracepoint
below guest_exit_irqoff() in vcpu_enter_guest(). Snapshot the delta before
VM-Enter, but trace it after VM-Exit. This can help us to move
wait_lapic_expire() just before vmentry in the later patch.

[1] Commit 8b89fe1f6c43 ("kvm: x86: move tracepoints outside extended quiescent state")
[2] https://patchwork.kernel.org/patch/7821111/

Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Radim Krčmář <rkrcmar@redhat.com>
Cc: Liran Alon <liran.alon@oracle.com>
Suggested-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Wanpeng Li <wanpengli@tencent.com>
[Track whether wait_lapic_expire was called, and do not invoke the tracepoint
 if not. - Paolo]
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
index c12b090f4fadee6bff585ef419f7e0433a68e1f6..f8615872ae64fc86169c12c58ed420be8e9b3489 100644 (file)
--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -1502,27 +1502,27 @@ static inline void __wait_lapic_expire(struct kvm_vcpu *vcpu, u64 guest_cycles)
 }
 
 static inline void adjust_lapic_timer_advance(struct kvm_vcpu *vcpu,
-                                             u64 guest_tsc, u64 tsc_deadline)
+                                             s64 advance_expire_delta)
 {
        struct kvm_lapic *apic = vcpu->arch.apic;
        u32 timer_advance_ns = apic->lapic_timer.timer_advance_ns;
        u64 ns;
 
        /* too early */
-       if (guest_tsc < tsc_deadline) {
-               ns = (tsc_deadline - guest_tsc) * 1000000ULL;
+       if (advance_expire_delta < 0) {
+               ns = -advance_expire_delta * 1000000ULL;
                do_div(ns, vcpu->arch.virtual_tsc_khz);
                timer_advance_ns -= min((u32)ns,
                        timer_advance_ns / LAPIC_TIMER_ADVANCE_ADJUST_STEP);
        } else {
        /* too late */
-               ns = (guest_tsc - tsc_deadline) * 1000000ULL;
+               ns = advance_expire_delta * 1000000ULL;
                do_div(ns, vcpu->arch.virtual_tsc_khz);
                timer_advance_ns += min((u32)ns,
                        timer_advance_ns / LAPIC_TIMER_ADVANCE_ADJUST_STEP);
        }
 
-       if (abs(guest_tsc - tsc_deadline) < LAPIC_TIMER_ADVANCE_ADJUST_DONE)
+       if (abs(advance_expire_delta) < LAPIC_TIMER_ADVANCE_ADJUST_DONE)
                apic->lapic_timer.timer_advance_adjust_done = true;
        if (unlikely(timer_advance_ns > 5000)) {
                timer_advance_ns = 0;
@@ -1545,13 +1545,13 @@ void 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());
-       trace_kvm_wait_lapic_expire(vcpu->vcpu_id, guest_tsc - tsc_deadline);
+       apic->lapic_timer.advance_expire_delta = guest_tsc - tsc_deadline;
 
        if (guest_tsc < tsc_deadline)
                __wait_lapic_expire(vcpu, tsc_deadline - guest_tsc);
 
        if (unlikely(!apic->lapic_timer.timer_advance_adjust_done))
-               adjust_lapic_timer_advance(vcpu, guest_tsc, tsc_deadline);
+               adjust_lapic_timer_advance(vcpu, apic->lapic_timer.advance_expire_delta);
 }
 
 static void start_sw_tscdeadline(struct kvm_lapic *apic)

diff --git a/arch/x86/kvm/lapic.h b/arch/x86/kvm/lapic.h
index d6d049ba304526be2974b2c4228b3a70420adbe7..3e72a255543d7b8f8db1acb28f1a3ee13c96d607 100644 (file)
--- a/arch/x86/kvm/lapic.h
+++ b/arch/x86/kvm/lapic.h
@@ -32,6 +32,7 @@ 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;
        bool timer_advance_adjust_done;

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index f3c0f2b63d769fe2d1a7d2b0fb3499d50e260f2e..7a26aa5b08614a02003bac77ab97a6b5d45697f2 100644 (file)
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -7980,6 +7980,13 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
        ++vcpu->stat.exits;
 
        guest_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();