arm/arm64: KVM: Require in-kernel vgic for the arch timers

It is curently possible to run a VM with architected timers support
without creating an in-kernel VGIC, which will result in interrupts from
the virtual timer going nowhere.

To address this issue, move the architected timers initialization to the
time when we run a VCPU for the first time, and then only initialize
(and enable) the architected timers if we have a properly created and
initialized in-kernel VGIC.

When injecting interrupts from the virtual timer to the vgic, the
current setup should ensure that this never calls an on-demand init of
the VGIC, which is the only call path that could return an error from
kvm_vgic_inject_irq(), so capture the return value and raise a warning
if there's an error there.

We also change the kvm_timer_init() function from returning an int to be
a void function, since the function always succeeds.

Reviewed-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>

1 files changed, 11 insertions, 2 deletions

diff --git a/arch/arm/kvm/arm.c b/arch/arm/kvm/arm.c
index 66f37c4cdf13..2d6d91001062 100644
--- a/arch/arm/kvm/arm.c
+++ b/arch/arm/kvm/arm.c
@@ -425,6 +425,7 @@ static void update_vttbr(struct kvm *kvm)
 
 static int kvm_vcpu_first_run_init(struct kvm_vcpu *vcpu)
 {
+        struct kvm *kvm = vcpu->kvm;
         int ret;
 
         if (likely(vcpu->arch.has_run_once))
@@ -436,12 +437,20 @@ static int kvm_vcpu_first_run_init(struct kvm_vcpu *vcpu)
          * Map the VGIC hardware resources before running a vcpu the first
          * time on this VM.
          */
-        if (unlikely(!vgic_ready(vcpu->kvm))) {
-                ret = kvm_vgic_map_resources(vcpu->kvm);
+        if (unlikely(!vgic_ready(kvm))) {
+                ret = kvm_vgic_map_resources(kvm);
                 if (ret)
                         return ret;
         }
 
+        /*
+         * Enable the arch timers only if we have an in-kernel VGIC
+         * and it has been properly initialized, since we cannot handle
+         * interrupts from the virtual timer with a userspace gic.
+         */
+        if (irqchip_in_kernel(kvm) && vgic_initialized(kvm))
+                kvm_timer_enable(kvm);
+
         return 0;
 }