KVM: x86: Switch KVM guest to using interrupts for page ready APF delivery

KVM now supports using interrupt for 'page ready' APF event delivery and
legacy mechanism was deprecated. Switch KVM guests to the new one.

Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Message-Id: <20200525144125.143875-9-vkuznets@redhat.com>
[Use HYPERVISOR_CALLBACK_VECTOR instead of a separate vector. - Paolo]
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

1 files changed, 33 insertions, 15 deletions

diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
index 7e6403a8d861..3a0115e8d880 100644
--- a/arch/x86/kernel/kvm.c
+++ b/arch/x86/kernel/kvm.c
@@ -233,15 +233,10 @@ NOKPROBE_SYMBOL(kvm_read_and_reset_apf_flags);
 
 bool __kvm_handle_async_pf(struct pt_regs *regs, u32 token)
 {
-	u32 reason = kvm_read_and_reset_apf_flags();
+	u32 flags = kvm_read_and_reset_apf_flags();
 
-	switch (reason) {
-	case KVM_PV_REASON_PAGE_NOT_PRESENT:
-	case KVM_PV_REASON_PAGE_READY:
-		break;
-	default:
+	if (!flags)
 		return false;
-	}
 
 	/*
 	 * If the host managed to inject an async #PF into an interrupt
@@ -251,19 +246,38 @@ bool __kvm_handle_async_pf(struct pt_regs *regs, u32 token)
 	if (unlikely(!(regs->flags & X86_EFLAGS_IF)))
 		panic("Host injected async #PF in interrupt disabled region\n");
 
-	if (reason == KVM_PV_REASON_PAGE_NOT_PRESENT) {
+	if (flags & KVM_PV_REASON_PAGE_NOT_PRESENT) {
 		if (unlikely(!(user_mode(regs))))
 			panic("Host injected async #PF in kernel mode\n");
 		/* Page is swapped out by the host. */
 		kvm_async_pf_task_wait_schedule(token);
-	} else {
+		return true;
+	}
+
+	WARN_ONCE(1, "Unexpected async PF flags: %x\n", flags);
+	return true;
+}
+NOKPROBE_SYMBOL(__kvm_handle_async_pf);
+
+__visible void __irq_entry kvm_async_pf_intr(struct pt_regs *regs)
+{
+	u32 token;
+
+	entering_ack_irq();
+
+	inc_irq_stat(irq_hv_callback_count);
+
+	if (__this_cpu_read(apf_reason.enabled)) {
+		token = __this_cpu_read(apf_reason.token);
 		rcu_irq_enter();
 		kvm_async_pf_task_wake(token);
 		rcu_irq_exit();
+		__this_cpu_write(apf_reason.token, 0);
+		wrmsrl(MSR_KVM_ASYNC_PF_ACK, 1);
 	}
-	return true;
+
+	exiting_irq();
 }
-NOKPROBE_SYMBOL(__kvm_handle_async_pf);
 
 static void __init paravirt_ops_setup(void)
 {
@@ -308,17 +322,19 @@ static notrace void kvm_guest_apic_eoi_write(u32 reg, u32 val)
 
 static void kvm_guest_cpu_init(void)
 {
-	if (kvm_para_has_feature(KVM_FEATURE_ASYNC_PF) && kvmapf) {
-		u64 pa;
+	if (kvm_para_has_feature(KVM_FEATURE_ASYNC_PF_INT) && kvmapf) {
+		u64 pa = slow_virt_to_phys(this_cpu_ptr(&apf_reason));
 
 		WARN_ON_ONCE(!static_branch_likely(&kvm_async_pf_enabled));
 
 		pa = slow_virt_to_phys(this_cpu_ptr(&apf_reason));
-		pa |= KVM_ASYNC_PF_ENABLED;
+		pa |= KVM_ASYNC_PF_ENABLED | KVM_ASYNC_PF_DELIVERY_AS_INT;
 
 		if (kvm_para_has_feature(KVM_FEATURE_ASYNC_PF_VMEXIT))
 			pa |= KVM_ASYNC_PF_DELIVERY_AS_PF_VMEXIT;
 
+		wrmsrl(MSR_KVM_ASYNC_PF_INT, HYPERVISOR_CALLBACK_VECTOR);
+
 		wrmsrl(MSR_KVM_ASYNC_PF_EN, pa);
 		__this_cpu_write(apf_reason.enabled, 1);
 		pr_info("KVM setup async PF for cpu %d\n", smp_processor_id());
@@ -643,8 +659,10 @@ static void __init kvm_guest_init(void)
 	if (kvm_para_has_feature(KVM_FEATURE_PV_EOI))
 		apic_set_eoi_write(kvm_guest_apic_eoi_write);
 
-	if (kvm_para_has_feature(KVM_FEATURE_ASYNC_PF) && kvmapf)
+	if (kvm_para_has_feature(KVM_FEATURE_ASYNC_PF_INT) && kvmapf) {
 		static_branch_enable(&kvm_async_pf_enabled);
+		alloc_intr_gate(HYPERVISOR_CALLBACK_VECTOR, kvm_async_pf_vector);
+	}
 
 #ifdef CONFIG_SMP
 	smp_ops.smp_prepare_cpus = kvm_smp_prepare_cpus;