KVM: Accelerated apic support

This adds a mechanism for exposing the virtual apic tpr to the guest, and a
protocol for letting the guest update the tpr without causing a vmexit if
conditions allow (e.g. there is no interrupt pending with a higher priority
than the new tpr).

Signed-off-by: Avi Kivity <avi@qumranet.com>

5 files changed, 120 insertions, 1 deletions

diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
index 50c3f3a8dd3d..e7513bb98af1 100644
--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -815,7 +815,8 @@ void kvm_lapic_set_tpr(struct kvm_vcpu *vcpu, unsigned long cr8)
 
         if (!apic)
                 return;
-        apic_set_tpr(apic, ((cr8 & 0x0f) << 4));
+        apic_set_tpr(apic, ((cr8 & 0x0f) << 4)
+                     | (apic_get_reg(apic, APIC_TASKPRI) & 4));
 }
 
 u64 kvm_lapic_get_cr8(struct kvm_vcpu *vcpu)
@@ -1104,3 +1105,51 @@ void kvm_migrate_apic_timer(struct kvm_vcpu *vcpu)
                 hrtimer_start(timer, timer->expires, HRTIMER_MODE_ABS);
 }
 EXPORT_SYMBOL_GPL(kvm_migrate_apic_timer);
+
+void kvm_lapic_sync_from_vapic(struct kvm_vcpu *vcpu)
+{
+        u32 data;
+        void *vapic;
+
+        if (!irqchip_in_kernel(vcpu->kvm) || !vcpu->arch.apic->vapic_addr)
+                return;
+
+        vapic = kmap_atomic(vcpu->arch.apic->vapic_page, KM_USER0);
+        data = *(u32 *)(vapic + offset_in_page(vcpu->arch.apic->vapic_addr));
+        kunmap_atomic(vapic, KM_USER0);
+
+        apic_set_tpr(vcpu->arch.apic, data & 0xff);
+}
+
+void kvm_lapic_sync_to_vapic(struct kvm_vcpu *vcpu)
+{
+        u32 data, tpr;
+        int max_irr, max_isr;
+        struct kvm_lapic *apic;
+        void *vapic;
+
+        if (!irqchip_in_kernel(vcpu->kvm) || !vcpu->arch.apic->vapic_addr)
+                return;
+
+        apic = vcpu->arch.apic;
+        tpr = apic_get_reg(apic, APIC_TASKPRI) & 0xff;
+        max_irr = apic_find_highest_irr(apic);
+        if (max_irr < 0)
+                max_irr = 0;
+        max_isr = apic_find_highest_isr(apic);
+        if (max_isr < 0)
+                max_isr = 0;
+        data = (tpr & 0xff) | ((max_isr & 0xf0) << 8) | (max_irr << 24);
+
+        vapic = kmap_atomic(vcpu->arch.apic->vapic_page, KM_USER0);
+        *(u32 *)(vapic + offset_in_page(vcpu->arch.apic->vapic_addr)) = data;
+        kunmap_atomic(vapic, KM_USER0);
+}
+
+void kvm_lapic_set_vapic_addr(struct kvm_vcpu *vcpu, gpa_t vapic_addr)
+{
+        if (!irqchip_in_kernel(vcpu->kvm))
+                return;
+
+        vcpu->arch.apic->vapic_addr = vapic_addr;
+}
diff --git a/arch/x86/kvm/lapic.h b/arch/x86/kvm/lapic.h
index 447b654aefbb..676c396c9cee 100644
--- a/arch/x86/kvm/lapic.h
+++ b/arch/x86/kvm/lapic.h
@@ -18,6 +18,8 @@ struct kvm_lapic {
         struct kvm_vcpu *vcpu;
         struct page *regs_page;
         void *regs;
+        gpa_t vapic_addr;
+        struct page *vapic_page;
 };
 int kvm_create_lapic(struct kvm_vcpu *vcpu);
 void kvm_free_lapic(struct kvm_vcpu *vcpu);
@@ -41,4 +43,8 @@ int kvm_lapic_enabled(struct kvm_vcpu *vcpu);
 int kvm_lapic_find_highest_irr(struct kvm_vcpu *vcpu);
 void kvm_apic_timer_intr_post(struct kvm_vcpu *vcpu, int vec);
 
+void kvm_lapic_set_vapic_addr(struct kvm_vcpu *vcpu, gpa_t vapic_addr);
+void kvm_lapic_sync_from_vapic(struct kvm_vcpu *vcpu);
+void kvm_lapic_sync_to_vapic(struct kvm_vcpu *vcpu);
+
 #endif
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index c2b80884447e..e7eac27adb7f 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -1173,6 +1173,19 @@ long kvm_arch_vcpu_ioctl(struct file *filp,
                 r = 0;
                 break;
         };
+        case KVM_SET_VAPIC_ADDR: {
+                struct kvm_vapic_addr va;
+
+                r = -EINVAL;
+                if (!irqchip_in_kernel(vcpu->kvm))
+                        goto out;
+                r = -EFAULT;
+                if (copy_from_user(&va, argp, sizeof va))
+                        goto out;
+                r = 0;
+                kvm_lapic_set_vapic_addr(vcpu, va.vapic_addr);
+                break;
+        }
         default:
                 r = -EINVAL;
         }
@@ -2214,6 +2227,9 @@ int kvm_emulate_hypercall(struct kvm_vcpu *vcpu)
         }
 
         switch (nr) {
+        case KVM_HC_VAPIC_POLL_IRQ:
+                ret = 0;
+                break;
         default:
                 ret = -KVM_ENOSYS;
                 break;
@@ -2421,6 +2437,29 @@ static void post_kvm_run_save(struct kvm_vcpu *vcpu,
                                          vcpu->arch.irq_summary == 0);
 }
 
+static void vapic_enter(struct kvm_vcpu *vcpu)
+{
+        struct kvm_lapic *apic = vcpu->arch.apic;
+        struct page *page;
+
+        if (!apic || !apic->vapic_addr)
+                return;
+
+        page = gfn_to_page(vcpu->kvm, apic->vapic_addr >> PAGE_SHIFT);
+        vcpu->arch.apic->vapic_page = page;
+}
+
+static void vapic_exit(struct kvm_vcpu *vcpu)
+{
+        struct kvm_lapic *apic = vcpu->arch.apic;
+
+        if (!apic || !apic->vapic_addr)
+                return;
+
+        kvm_release_page_dirty(apic->vapic_page);
+        mark_page_dirty(vcpu->kvm, apic->vapic_addr >> PAGE_SHIFT);
+}
+
 static int __vcpu_run(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
 {
         int r;
@@ -2435,6 +2474,8 @@ static int __vcpu_run(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
                 vcpu->arch.mp_state = VCPU_MP_STATE_RUNNABLE;
         }
 
+        vapic_enter(vcpu);
+
 preempted:
         if (vcpu->guest_debug.enabled)
                 kvm_x86_ops->guest_debug_pre(vcpu);
@@ -2444,6 +2485,14 @@ again:
         if (unlikely(r))
                 goto out;
 
+        if (vcpu->requests)
+                if (test_and_clear_bit(KVM_REQ_REPORT_TPR_ACCESS,
+                                       &vcpu->requests)) {
+                        kvm_run->exit_reason = KVM_EXIT_TPR_ACCESS;
+                        r = 0;
+                        goto out;
+                }
+
         kvm_inject_pending_timer_irqs(vcpu);
 
         preempt_disable();
@@ -2469,6 +2518,8 @@ again:
         else
                 kvm_x86_ops->inject_pending_vectors(vcpu, kvm_run);
 
+        kvm_lapic_sync_to_vapic(vcpu);
+
         vcpu->guest_mode = 1;
         kvm_guest_enter();
 
@@ -2506,6 +2557,8 @@ again:
         if (vcpu->arch.exception.pending && kvm_x86_ops->exception_injected(vcpu))
                 vcpu->arch.exception.pending = false;
 
+        kvm_lapic_sync_from_vapic(vcpu);
+
         r = kvm_x86_ops->handle_exit(kvm_run, vcpu);
 
         if (r > 0) {
@@ -2527,6 +2580,8 @@ out:
 
         post_kvm_run_save(vcpu, kvm_run);
 
+        vapic_exit(vcpu);
+
         return r;
 }
 
diff --git a/include/linux/kvm.h b/include/linux/kvm.h
index 850f5ef76636..b27a381db5e8 100644
--- a/include/linux/kvm.h
+++ b/include/linux/kvm.h
@@ -216,6 +216,11 @@ struct kvm_tpr_access_ctl {
         __u32 reserved[8];
 };
 
+/* for KVM_SET_VAPIC_ADDR */
+struct kvm_vapic_addr {
+        __u64 vapic_addr;
+};
+
 #define KVMIO 0xAE
 
 /*
@@ -291,5 +296,7 @@ struct kvm_tpr_access_ctl {
 #define KVM_GET_CPUID2            _IOWR(KVMIO, 0x91, struct kvm_cpuid2)
 /* Available with KVM_CAP_VAPIC */
 #define KVM_TPR_ACCESS_REPORTING  _IOWR(KVMIO,  0x92, struct kvm_tpr_access_ctl)
+/* Available with KVM_CAP_VAPIC */
+#define KVM_SET_VAPIC_ADDR        _IOW(KVMIO,  0x93, struct kvm_vapic_addr)
 
 #endif
diff --git a/include/linux/kvm_para.h b/include/linux/kvm_para.h
index e4db25ffdb52..6af91a506fbf 100644
--- a/include/linux/kvm_para.h
+++ b/include/linux/kvm_para.h
@@ -12,6 +12,8 @@
 /* Return values for hypercalls */
 #define KVM_ENOSYS              1000
 
+#define KVM_HC_VAPIC_POLL_IRQ            1
+
 #ifdef __KERNEL__
 /*
  * hypercalls use architecture specific