* [PATCH] KVM: LAPIC: Fix advance timer expiration delta trace
@ 2022-04-26 8:25 Wanpeng Li
2022-05-03 12:18 ` Paolo Bonzini
0 siblings, 1 reply; 2+ messages in thread
From: Wanpeng Li @ 2022-04-26 8:25 UTC (permalink / raw
To: linux-kernel, kvm
Cc: Paolo Bonzini, Sean Christopherson, Vitaly Kuznetsov, Wanpeng Li,
Jim Mattson, Joerg Roedel
From: Wanpeng Li <wanpengli@tencent.com>
The advance timer expiration delta trace is moved after guest_exit_irqoff()
since it can avoid to violate RCU extended quiescent state when moving
wait_lapic_expire() just before vmentry. Now kvm can enter a guest multiple
times since IPI/Timer fastpath, snapshot the delta multiple times before
vmentry and trace it one time after vmexit is not accurately this time.
Commit 87fa7f3e98a1 (x86/kvm: Move context tracking where it belongs) moves
rcu state updates more closer around vmentry/vmexit, we will not violate RCU
any more. Let's fix it by keeping the advance timer expiration delta trace
in __kvm_wait_lapic_epire() and dropping advance_expire_delta.
Signed-off-by: Wanpeng Li <wanpengli@tencent.com>
---
arch/x86/kvm/lapic.c | 4 ++--
arch/x86/kvm/lapic.h | 1 -
arch/x86/kvm/x86.c | 8 --------
3 files changed, 2 insertions(+), 11 deletions(-)
diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
index 66b0eb0bda94..a4e9eb329e42 100644
--- 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 4e4f8a22754f..65bb2a8cf145 100644
--- 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 a6ab19afc638..5fa465b268d2 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -10248,14 +10248,6 @@ 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();
--
2.25.1
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH] KVM: LAPIC: Fix advance timer expiration delta trace
2022-04-26 8:25 [PATCH] KVM: LAPIC: Fix advance timer expiration delta trace Wanpeng Li
@ 2022-05-03 12:18 ` Paolo Bonzini
0 siblings, 0 replies; 2+ messages in thread
From: Paolo Bonzini @ 2022-05-03 12:18 UTC (permalink / raw
To: Wanpeng Li
Cc: linux-kernel, kvm, Sean Christopherson, Vitaly Kuznetsov,
Wanpeng Li, Jim Mattson, Joerg Roedel
Queued, thanks.
Paolo
^ permalink raw reply [flat|nested] 2+ messages in thread
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2022-05-03 12:18 ` Paolo Bonzini
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