KVM: arm-vgic: Support KVM_CREATE_DEVICE for VGIC

Support creating the ARM VGIC device through the KVM_CREATE_DEVICE
ioctl, which can then later be leveraged to use the
KVM_{GET/SET}_DEVICE_ATTR, which is useful both for setting addresses in
a more generic API than the ARM-specific one and is useful for
save/restore of VGIC state.

Adds KVM_CAP_DEVICE_CTRL to ARM capabilities.

Note that we change the check for creating a VGIC from bailing out if
any VCPUs were created, to bailing out if any VCPUs were ever run.  This
is an important distinction that shouldn't break anything, but allows
creating the VGIC after the VCPUs have been created.

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

1 files changed, 61 insertions, 2 deletions

diff --git a/virt/kvm/arm/vgic.c b/virt/kvm/arm/vgic.c
index 5e9df47778fb..b15d6c17a090 100644
--- a/virt/kvm/arm/vgic.c
+++ b/virt/kvm/arm/vgic.c
@@ -1433,20 +1433,45 @@ out:
 
 int kvm_vgic_create(struct kvm *kvm)
 {
-        int ret = 0;
+        int i, vcpu_lock_idx = -1, ret = 0;
+        struct kvm_vcpu *vcpu;
 
         mutex_lock(&kvm->lock);
 
-        if (atomic_read(&kvm->online_vcpus) || kvm->arch.vgic.vctrl_base) {
+        if (kvm->arch.vgic.vctrl_base) {
                 ret = -EEXIST;
                 goto out;
         }
 
+        /*
+         * Any time a vcpu is run, vcpu_load is called which tries to grab the
+         * vcpu->mutex.  By grabbing the vcpu->mutex of all VCPUs we ensure
+         * that no other VCPUs are run while we create the vgic.
+         */
+        kvm_for_each_vcpu(i, vcpu, kvm) {
+                if (!mutex_trylock(&vcpu->mutex))
+                        goto out_unlock;
+                vcpu_lock_idx = i;
+        }
+
+        kvm_for_each_vcpu(i, vcpu, kvm) {
+                if (vcpu->arch.has_run_once) {
+                        ret = -EBUSY;
+                        goto out_unlock;
+                }
+        }
+
         spin_lock_init(&kvm->arch.vgic.lock);
         kvm->arch.vgic.vctrl_base = vgic_vctrl_base;
         kvm->arch.vgic.vgic_dist_base = VGIC_ADDR_UNDEF;
         kvm->arch.vgic.vgic_cpu_base = VGIC_ADDR_UNDEF;
 
+out_unlock:
+        for (; vcpu_lock_idx >= 0; vcpu_lock_idx--) {
+                vcpu = kvm_get_vcpu(kvm, vcpu_lock_idx);
+                mutex_unlock(&vcpu->mutex);
+        }
+
 out:
         mutex_unlock(&kvm->lock);
         return ret;
@@ -1510,3 +1535,37 @@ int kvm_vgic_set_addr(struct kvm *kvm, unsigned long type, u64 addr)
         mutex_unlock(&kvm->lock);
         return r;
 }
+
+static int vgic_set_attr(struct kvm_device *dev, struct kvm_device_attr *attr)
+{
+        return -ENXIO;
+}
+
+static int vgic_get_attr(struct kvm_device *dev, struct kvm_device_attr *attr)
+{
+        return -ENXIO;
+}
+
+static int vgic_has_attr(struct kvm_device *dev, struct kvm_device_attr *attr)
+{
+        return -ENXIO;
+}
+
+static void vgic_destroy(struct kvm_device *dev)
+{
+        kfree(dev);
+}
+
+static int vgic_create(struct kvm_device *dev, u32 type)
+{
+        return kvm_vgic_create(dev->kvm);
+}
+
+struct kvm_device_ops kvm_arm_vgic_v2_ops = {
+        .name = "kvm-arm-vgic",
+        .create = vgic_create,
+        .destroy = vgic_destroy,
+        .set_attr = vgic_set_attr,
+        .get_attr = vgic_get_attr,
+        .has_attr = vgic_has_attr,
+};