From 3227a2bdc7a494194a6a4f7d5653ff178ecb1b2f Mon Sep 17 00:00:00 2001
From: Alexander Graf <agraf@suse.de>
Date: Mon, 19 Sep 2016 10:02:55 +0200
Subject: [PATCH] ARM: KVM: Enable in-kernel timers with user space gic

When running with KVM enabled, you can choose between emulating the
gic in kernel or user space. If the kernel supports in-kernel virtualization
of the interrupt controller, it will default to that. If not, if will
default to user space emulation.

Unfortunately when running in user mode gic emulation, we miss out on
timer events which are only available from kernel space. This patch leverages
the new kernel/user space pending line synchronization for those timer events.

Signed-off-by: Alexander Graf <agraf@suse.de>
---
 hw/arm/virt.c    | 10 ++++++++++
 target/arm/cpu.h |  3 +++
 target/arm/kvm.c | 31 ++++++++++++++++++++++++++++++-
 3 files changed, 43 insertions(+), 1 deletion(-)

diff --git a/hw/arm/virt.c b/hw/arm/virt.c
index 5f62a0321e..a1d24a4db6 100644
--- a/hw/arm/virt.c
+++ b/hw/arm/virt.c
@@ -609,6 +609,16 @@ static void create_gic(VirtMachineState *vms, qemu_irq *pic)
     } else if (type == 2) {
         create_v2m(vms, pic);
     }
+
+#ifdef CONFIG_KVM
+    if (kvm_enabled() && !kvm_irqchip_in_kernel()) {
+        if (!kvm_check_extension(kvm_state, KVM_CAP_ARM_USER_IRQ)) {
+            error_report("KVM with user space irqchip only works when the "
+                         "host kernel supports KVM_CAP_ARM_USER_IRQ");
+            exit(1);
+        }
+    }
+#endif
 }
 
 static void create_uart(const VirtMachineState *vms, qemu_irq *pic, int uart,
diff --git a/target/arm/cpu.h b/target/arm/cpu.h
index a8aabce7dd..19cb596449 100644
--- a/target/arm/cpu.h
+++ b/target/arm/cpu.h
@@ -702,6 +702,9 @@ struct ARMCPU {
 
     ARMELChangeHook *el_change_hook;
     void *el_change_hook_opaque;
+
+    /* Used to synchronize KVM and QEMU timer levels */
+    uint64_t device_irq_level;
 };
 
 static inline ARMCPU *arm_env_get_cpu(CPUARMState *env)
diff --git a/target/arm/kvm.c b/target/arm/kvm.c
index 45554682f2..dccb326615 100644
--- a/target/arm/kvm.c
+++ b/target/arm/kvm.c
@@ -174,6 +174,12 @@ int kvm_arch_init(MachineState *ms, KVMState *s)
      */
     kvm_async_interrupts_allowed = true;
 
+    /*
+     * PSCI wakes up secondary cores, so we always need to
+     * have vCPUs waiting in kernel space
+     */
+    kvm_halt_in_kernel_allowed = true;
+
     cap_has_mp_state = kvm_check_extension(s, KVM_CAP_MP_STATE);
 
     type_register_static(&host_arm_cpu_type_info);
@@ -528,10 +534,33 @@ void kvm_arch_pre_run(CPUState *cs, struct kvm_run *run)
 
 MemTxAttrs kvm_arch_post_run(CPUState *cs, struct kvm_run *run)
 {
+    ARMCPU *cpu;
+
+    if (kvm_irqchip_in_kernel()) {
+        /*
+         * We only need to sync timer states with user-space interrupt
+         * controllers, so return early and save cycles if we don't.
+         */
+        return MEMTXATTRS_UNSPECIFIED;
+    }
+
+    cpu = ARM_CPU(cs);
+
+    /* Synchronize our internal vtimer irq line with the kvm one */
+    if (run->s.regs.device_irq_level != cpu->device_irq_level) {
+        qemu_mutex_lock_iothread();
+        qemu_set_irq(cpu->gt_timer_outputs[GTIMER_VIRT],
+                      run->s.regs.device_irq_level & KVM_ARM_DEV_EL1_VTIMER);
+        qemu_set_irq(cpu->gt_timer_outputs[GTIMER_PHYS],
+                     run->s.regs.device_irq_level & KVM_ARM_DEV_EL1_PTIMER);
+        /* TODO: Handle changes in PMU as well */
+        cpu->device_irq_level = run->s.regs.device_irq_level;
+        qemu_mutex_unlock_iothread();
+    }
+
     return MEMTXATTRS_UNSPECIFIED;
 }
 
-
 int kvm_arch_handle_exit(CPUState *cs, struct kvm_run *run)
 {
     int ret = 0;