linux-kernel - [PATCH v3 4/5] KVM: X86: TSCDEADLINE MSR emulation fastpath

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Message-Id: <1587709364-19090-5-git-send-email-wanpengli@tencent.com>
Date:   Fri, 24 Apr 2020 14:22:43 +0800
From:   Wanpeng Li <kernellwp@...il.com>
To:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Cc:     Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>,
        Haiwei Li <lihaiwei@...cent.com>
Subject: [PATCH v3 4/5] KVM: X86: TSCDEADLINE MSR emulation fastpath

From: Wanpeng Li <wanpengli@...cent.com>

This patch implements tscdealine msr emulation fastpath, after wrmsr 
tscdeadline vmexit, handle it as soon as possible and vmentry immediately 
without checking various kvm stuff when possible.

Tested-by: Haiwei Li <lihaiwei@...cent.com>
Cc: Haiwei Li <lihaiwei@...cent.com>
Signed-off-by: Wanpeng Li <wanpengli@...cent.com>
---
 arch/x86/kvm/lapic.c | 18 ++++++++++++------
 arch/x86/kvm/x86.c   | 30 ++++++++++++++++++++++++------
 2 files changed, 36 insertions(+), 12 deletions(-)

diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
index 38f7dc9..3589237 100644
--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -1593,7 +1593,7 @@ static void kvm_apic_inject_pending_timer_irqs(struct kvm_lapic *apic)
 	}
 }
 
-static void apic_timer_expired(struct kvm_lapic *apic)
+static void apic_timer_expired(struct kvm_lapic *apic, bool from_timer_fn)
 {
 	struct kvm_vcpu *vcpu = apic->vcpu;
 	struct kvm_timer *ktimer = &apic->lapic_timer;
@@ -1604,6 +1604,12 @@ static void apic_timer_expired(struct kvm_lapic *apic)
 	if (apic_lvtt_tscdeadline(apic) || ktimer->hv_timer_in_use)
 		ktimer->expired_tscdeadline = ktimer->tscdeadline;
 
+	if (!from_timer_fn && vcpu->arch.apicv_active) {
+		WARN_ON(kvm_get_running_vcpu() != vcpu);
+		kvm_apic_inject_pending_timer_irqs(apic);
+		return;
+	}
+
 	if (kvm_use_posted_timer_interrupt(apic->vcpu)) {
 		if (apic->lapic_timer.timer_advance_ns)
 			__kvm_wait_lapic_expire(vcpu);
@@ -1643,7 +1649,7 @@ static void start_sw_tscdeadline(struct kvm_lapic *apic)
 		expire = ktime_sub_ns(expire, ktimer->timer_advance_ns);
 		hrtimer_start(&ktimer->timer, expire, HRTIMER_MODE_ABS_HARD);
 	} else
-		apic_timer_expired(apic);
+		apic_timer_expired(apic, false);
 
 	local_irq_restore(flags);
 }
@@ -1751,7 +1757,7 @@ static void start_sw_period(struct kvm_lapic *apic)
 
 	if (ktime_after(ktime_get(),
 			apic->lapic_timer.target_expiration)) {
-		apic_timer_expired(apic);
+		apic_timer_expired(apic, false);
 
 		if (apic_lvtt_oneshot(apic))
 			return;
@@ -1813,7 +1819,7 @@ static bool start_hv_timer(struct kvm_lapic *apic)
 		if (atomic_read(&ktimer->pending)) {
 			cancel_hv_timer(apic);
 		} else if (expired) {
-			apic_timer_expired(apic);
+			apic_timer_expired(apic, false);
 			cancel_hv_timer(apic);
 		}
 	}
@@ -1863,7 +1869,7 @@ void kvm_lapic_expired_hv_timer(struct kvm_vcpu *vcpu)
 		goto out;
 	WARN_ON(swait_active(&vcpu->wq));
 	cancel_hv_timer(apic);
-	apic_timer_expired(apic);
+	apic_timer_expired(apic, false);
 
 	if (apic_lvtt_period(apic) && apic->lapic_timer.period) {
 		advance_periodic_target_expiration(apic);
@@ -2369,7 +2375,7 @@ static enum hrtimer_restart apic_timer_fn(struct hrtimer *data)
 	struct kvm_timer *ktimer = container_of(data, struct kvm_timer, timer);
 	struct kvm_lapic *apic = container_of(ktimer, struct kvm_lapic, lapic_timer);
 
-	apic_timer_expired(apic);
+	apic_timer_expired(apic, true);
 
 	if (lapic_is_periodic(apic)) {
 		advance_periodic_target_expiration(apic);
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 4561104..99061ba 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -1616,27 +1616,45 @@ static int handle_fastpath_set_x2apic_icr_irqoff(struct kvm_vcpu *vcpu, u64 data
 	return 1;
 }
 
+static int handle_fastpath_set_tscdeadline(struct kvm_vcpu *vcpu, u64 data)
+{
+	if (!kvm_x86_ops.set_hv_timer ||
+		kvm_mwait_in_guest(vcpu->kvm) ||
+		kvm_can_post_timer_interrupt(vcpu))
+		return 1;
+
+	kvm_set_lapic_tscdeadline_msr(vcpu, data);
+	return 0;
+}
+
 enum exit_fastpath_completion handle_fastpath_set_msr_irqoff(struct kvm_vcpu *vcpu)
 {
 	u32 msr = kvm_rcx_read(vcpu);
 	u64 data;
-	int ret = 0;
+	int ret = EXIT_FASTPATH_NONE;
 
 	switch (msr) {
 	case APIC_BASE_MSR + (APIC_ICR >> 4):
 		data = kvm_read_edx_eax(vcpu);
-		ret = handle_fastpath_set_x2apic_icr_irqoff(vcpu, data);
+		if (!handle_fastpath_set_x2apic_icr_irqoff(vcpu, data))
+			ret = EXIT_FASTPATH_SKIP_EMUL_INS;
+		break;
+	case MSR_IA32_TSCDEADLINE:
+		data = kvm_read_edx_eax(vcpu);
+		if (!handle_fastpath_set_tscdeadline(vcpu, data))
+			ret = EXIT_FASTPATH_CONT_RUN;
 		break;
 	default:
-		return EXIT_FASTPATH_NONE;
+		ret = EXIT_FASTPATH_NONE;
 	}
 
-	if (!ret) {
+	if (ret != EXIT_FASTPATH_NONE) {
 		trace_kvm_msr_write(msr, data);
-		return EXIT_FASTPATH_SKIP_EMUL_INS;
+		if (ret == EXIT_FASTPATH_CONT_RUN)
+			kvm_skip_emulated_instruction(vcpu);
 	}
 
-	return EXIT_FASTPATH_NONE;
+	return ret;
 }
 EXPORT_SYMBOL_GPL(handle_fastpath_set_msr_irqoff);
 
-- 
2.7.4