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KVM: LAPIC: Trace LAPIC timer expiration on every vmentry

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In commit ec0671d568 ("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 87fa7f3e98 ("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>
This commit is contained in:
Wanpeng Li 2022-04-26 01:25:51 -07:00 committed by Paolo Bonzini
parent 6ba1e04fa6
commit e0ac535178
3 changed files with 2 additions and 11 deletions
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4
arch/x86/kvm/lapic.c
View File

@ -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

1
arch/x86/kvm/lapic.h
View File

@ -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;
};

8
arch/x86/kvm/x86.c
View File

@ -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();