From ec0671d5684aca3326269439398e47790f1c6e7e Mon Sep 17 00:00:00 2001 From: Wanpeng Li Date: Mon, 20 May 2019 16:18:08 +0800 Subject: [PATCH] KVM: LAPIC: Delay trace_kvm_wait_lapic_expire tracepoint to after vmexit MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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 Cc: Radim Krčmář Cc: Liran Alon Suggested-by: Sean Christopherson Signed-off-by: Wanpeng Li [Track whether wait_lapic_expire was called, and do not invoke the tracepoint if not. - Paolo] Signed-off-by: Paolo Bonzini --- arch/x86/kvm/lapic.c | 14 +++++++------- arch/x86/kvm/lapic.h | 1 + arch/x86/kvm/x86.c | 7 +++++++ 3 files changed, 15 insertions(+), 7 deletions(-) diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c index c12b090f4fad..f8615872ae64 100644 --- 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 d6d049ba3045..3e72a255543d 100644 --- 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 f3c0f2b63d76..7a26aa5b0861 100644 --- 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();