On 20/05/19 10:18, Wanpeng Li wrote:
> From: Wanpeng Li <wanpen...@tencent.com>
>
> 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/
This is a bit confusing, since the delta is printed after the
corresponding vmexit but the wait is done before the vmentry. I think
we can drop the tracepoint:
------------- 8< ----------------
>From ae148d98d49b96b5222e2c78ac1b1e13cc526d71 Mon Sep 17 00:00:00 2001
From: Paolo Bonzini <pbonz...@redhat.com>
Date: Mon, 20 May 2019 13:10:01 +0200
Subject: [PATCH] KVM: lapic: replace wait_lapic_expire tracepoint with
restart_apic_timer
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].
We would like to move wait_lapic_expire() just before vmentry, which would
place wait_lapic_expire() again inside the extended quiescent state. Drop
the tracepoint, but add instead another one that can be useful and where
we can check the status of the adaptive tuning procedure.
[1] Commit 8b89fe1f6c43 ("kvm: x86: move tracepoints outside extended quiescent
state")
[2] https://patchwork.kernel.org/patch/7821111/
Signed-off-by: Paolo Bonzini <pbonz...@redhat.com>
---
arch/x86/kvm/lapic.c | 4 +++-
arch/x86/kvm/trace.h | 15 +++++++--------
2 files changed, 10 insertions(+), 9 deletions(-)
diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
index c12b090f4fad..8f05c1d0b486 100644
--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -1545,7 +1545,6 @@ 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);
if (guest_tsc < tsc_deadline)
__wait_lapic_expire(vcpu, tsc_deadline - guest_tsc);
@@ -1763,6 +1762,9 @@ static void start_sw_timer(struct kvm_lapic *apic)
static void restart_apic_timer(struct kvm_lapic *apic)
{
+ trace_kvm_restart_apic_timer(apic->vcpu->vcpu_id,
+ apic->lapic_timer.timer_advance_ns);
+
preempt_disable();
if (!apic_lvtt_period(apic) && atomic_read(&apic->lapic_timer.pending))
diff --git a/arch/x86/kvm/trace.h b/arch/x86/kvm/trace.h
index 4d47a2631d1f..f6e000038f3f 100644
--- a/arch/x86/kvm/trace.h
+++ b/arch/x86/kvm/trace.h
@@ -953,24 +953,23 @@
__entry->flags)
);
-TRACE_EVENT(kvm_wait_lapic_expire,
- TP_PROTO(unsigned int vcpu_id, s64 delta),
- TP_ARGS(vcpu_id, delta),
+TRACE_EVENT(kvm_restart_apic_timer,
+ TP_PROTO(unsigned int vcpu_id, u32 advance),
+ TP_ARGS(vcpu_id, advance),
TP_STRUCT__entry(
__field( unsigned int, vcpu_id )
- __field( s64, delta )
+ __field( u32, advance )
),
TP_fast_assign(
__entry->vcpu_id = vcpu_id;
- __entry->delta = delta;
+ __entry->advance = advance;
),
- TP_printk("vcpu %u: delta %lld (%s)",
+ TP_printk("vcpu %u: advance %u",
__entry->vcpu_id,
- __entry->delta,
- __entry->delta < 0 ? "early" : "late")
+ __entry->advance)
);
TRACE_EVENT(kvm_enter_smm,
