Subject: [PATCH 02/10] KVM: arm-vgic: Support KVM_CREATE_DEVICE for VGIC

From: [email-masked] (Marc Zyngier)
Date: Mon, 16 Dec 2013 11:45:21 +0000

On 12/12/13 19:55, Christoffer Dall wrote:
> 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.
> 
> Signed-off-by: Christoffer Dall <[email-masked]>
> ---
> Changelog[v4]:
>  - Rename kvm_arm_vgic_ops to kvm_arm_vgic_v2_ops
>  - Add comment to kvm_vgic_create about locking vcpu->mutex
> 
> Changelog[v3]:
>  - Prevent race in kvm_vgic_create by trying to take all the vcpu
>    locks before creating the vgic.
> 
> Changelog[v2]:
>  - None
> 
>  Documentation/virtual/kvm/devices/arm-vgic.txt | 10 ++++
>  arch/arm/kvm/arm.c                             |  1 +
>  include/linux/kvm_host.h                       |  1 +
>  include/uapi/linux/kvm.h                       |  1 +
>  virt/kvm/arm/vgic.c                            | 63 +++++++++++++++++++++++++-
>  virt/kvm/kvm_main.c                            |  6 ++-
>  6 files changed, 79 insertions(+), 3 deletions(-)
>  create mode 100644 Documentation/virtual/kvm/devices/arm-vgic.txt
> 
> diff --git a/Documentation/virtual/kvm/devices/arm-vgic.txt b/Documentation/virtual/kvm/devices/arm-vgic.txt
> new file mode 100644
> index 0000000..38f27f7
> --- /dev/null
> +++ b/Documentation/virtual/kvm/devices/arm-vgic.txt
> @@ -0,0 +1,10 @@
> +ARM Virtual Generic Interrupt Controller (VGIC)
> +===============================================
> +
> +Device types supported:
> +  KVM_DEV_TYPE_ARM_VGIC_V2     ARM Generic Interrupt Controller v2.0
> +
> +Only one VGIC instance may be instantiated through either this API or the
> +legacy KVM_CREATE_IRQCHIP api.  The created VGIC will act as the VM interrupt
> +controller, requiring emulated user-space devices to inject interrupts to the
> +VGIC instead of directly to CPUs.
> diff --git a/arch/arm/kvm/arm.c b/arch/arm/kvm/arm.c
> index c9fe9d7..cc7c41a 100644
> --- a/arch/arm/kvm/arm.c
> +++ b/arch/arm/kvm/arm.c
> @@ -190,6 +190,7 @@ int kvm_dev_ioctl_check_extension(long ext)
>  	case KVM_CAP_IRQCHIP:
>  		r = vgic_present;
>  		break;
> +	case KVM_CAP_DEVICE_CTRL:
>  	case KVM_CAP_USER_MEMORY:
>  	case KVM_CAP_SYNC_MMU:
>  	case KVM_CAP_DESTROY_MEMORY_REGION_WORKS:
> diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
> index 9523d2a..521dd76 100644
> --- a/include/linux/kvm_host.h
> +++ b/include/linux/kvm_host.h
> @@ -1076,6 +1076,7 @@ struct kvm_device *kvm_device_from_filp(struct file *filp);
>  extern struct kvm_device_ops kvm_mpic_ops;
>  extern struct kvm_device_ops kvm_xics_ops;
>  extern struct kvm_device_ops kvm_vfio_ops;
> +extern struct kvm_device_ops kvm_arm_vgic_v2_ops;
>  
>  #ifdef CONFIG_HAVE_KVM_CPU_RELAX_INTERCEPT
>  
> diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
> index 902f124..b647c29 100644
> --- a/include/uapi/linux/kvm.h
> +++ b/include/uapi/linux/kvm.h
> @@ -853,6 +853,7 @@ struct kvm_device_attr {
>  #define  KVM_DEV_VFIO_GROUP			1
>  #define   KVM_DEV_VFIO_GROUP_ADD			1
>  #define   KVM_DEV_VFIO_GROUP_DEL			2
> +#define KVM_DEV_TYPE_ARM_VGIC_V2	5
>  
>  /*
>   * ioctls for VM fds
> diff --git a/virt/kvm/arm/vgic.c b/virt/kvm/arm/vgic.c
> index 5e9df47..b15d6c1 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,
> +};
> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> index a0aa84b..954a0ba 100644
> --- a/virt/kvm/kvm_main.c
> +++ b/virt/kvm/kvm_main.c
> @@ -2279,7 +2279,11 @@ static int kvm_ioctl_create_device(struct kvm *kvm,
>  #ifdef CONFIG_KVM_VFIO
>  	case KVM_DEV_TYPE_VFIO:
>  		ops = &kvm_vfio_ops;
> -		break;

I think you just broke VFIO.

> +#endif
> +#ifdef CONFIG_KVM_ARM_VGIC
> +	case KVM_DEV_TYPE_ARM_VGIC_V2:
> +		ops = &kvm_arm_vgic_v2_ops;
> +	break;

Indentation?

>  #endif
>  	default:
>  		return -ENODEV;

Provided that you fix the above:
Acked-by: Marc Zyngier <[email-masked]>

	M.
-- 
Jazz is not dead. It just smells funny...