[PATCH] KVM: arm64: ITS: move ITS registration into first VCPU run

[eric.auger@redhat.com (Auger Eric)]

Hi

On 03/08/2016 19:48, Auger Eric wrote:
> Hi Andre, Christoffer,
> 
> On 03/08/2016 19:18, Andre Przywara wrote:
>> Hi,
>>
>> On 03/08/16 18:11, Christoffer Dall wrote:
>>> On Wed, Aug 03, 2016 at 03:57:45PM +0100, Andre Przywara wrote:
>>>> Currently we register ITS devices upon userland issuing the CTRL_INIT
>>>> ioctl to mark initialization of the ITS as done.
>>>> This deviates from the initialization sequence of the existing GIC
>>>> devices and does not play well with the way QEMU handles things.
>>>> To be more in line with what we are used to, register the ITS(es) just
>>>> before the first VCPU is about to run, so in the map_resources() call.
>>>> This involves iterating through the list of KVM devices and handle each
>>>> ITS that we find.
>>>>
>>>> Signed-off-by: Andre Przywara <andre.przywara@arm.com>
>>>> ---
>>>> Hi,
>>>>
>>>> this is based upon next-20160728 plus Christoffer's kvm_device locking
>>>> fix from today. Please let me know what tree I should base upon and I
>>>> will rebase.
>>>> Eric, Christoffer: does that do what you expect? Can QEMU live with that?
>>>>
>>>> Cheers,
>>>> Andre.
>>>>
>>>>  virt/kvm/arm/vgic/vgic-its.c | 56 ++++++++++++++++++++++++++++++++++++--------
>>>>  virt/kvm/arm/vgic/vgic-v3.c  |  6 +++++
>>>>  virt/kvm/arm/vgic/vgic.h     |  6 +++++
>>>>  3 files changed, 58 insertions(+), 10 deletions(-)
>>>>
>>>> diff --git a/virt/kvm/arm/vgic/vgic-its.c b/virt/kvm/arm/vgic/vgic-its.c
>>>> index 07411cf..e677a60 100644
>>>> --- a/virt/kvm/arm/vgic/vgic-its.c
>>>> +++ b/virt/kvm/arm/vgic/vgic-its.c
>>>> @@ -1288,13 +1288,13 @@ void vgic_enable_lpis(struct kvm_vcpu *vcpu)
>>>>  		its_sync_lpi_pending_table(vcpu);
>>>>  }
>>>>  
>>>> -static int vgic_its_init_its(struct kvm *kvm, struct vgic_its *its)
>>>> +static int vgic_register_its_iodev(struct kvm *kvm, struct vgic_its *its)
>>>>  {
>>>>  	struct vgic_io_device *iodev = &its->iodev;
>>>>  	int ret;
>>>>  
>>>> -	if (its->initialized)
>>>> -		return 0;
>>>> +	if (!its->initialized)
>>>> +		return -EBUSY;
>>>>  
>>>>  	if (IS_VGIC_ADDR_UNDEF(its->vgic_its_base))
>>>>  		return -ENXIO;
>>>> @@ -1311,9 +1311,6 @@ static int vgic_its_init_its(struct kvm *kvm, struct vgic_its *its)
>>>>  				      KVM_VGIC_V3_ITS_SIZE, &iodev->dev);
>>>>  	mutex_unlock(&kvm->slots_lock);
>>>>  
>>>> -	if (!ret)
>>>> -		its->initialized = true;
>>>> -
>>>>  	return ret;
>>>>  }
>>>>  
>>>> @@ -1435,9 +1432,6 @@ static int vgic_its_set_attr(struct kvm_device *dev,
>>>>  		if (type != KVM_VGIC_ITS_ADDR_TYPE)
>>>>  			return -ENODEV;
>>>>  
>>>> -		if (its->initialized)
>>>> -			return -EBUSY;
>>>> -
>>>>  		if (copy_from_user(&addr, uaddr, sizeof(addr)))
>>>>  			return -EFAULT;
>>>>  
>>>> @@ -1453,7 +1447,9 @@ static int vgic_its_set_attr(struct kvm_device *dev,
>>>>  	case KVM_DEV_ARM_VGIC_GRP_CTRL:
>>>>  		switch (attr->attr) {
>>>>  		case KVM_DEV_ARM_VGIC_CTRL_INIT:
>>>> -			return vgic_its_init_its(dev->kvm, its);
>>>> +			its->initialized = true;
>>>> +
>>>> +			return 0;
>>>>  		}
>>>>  		break;
>>>>  	}
>>>> @@ -1498,3 +1494,43 @@ int kvm_vgic_register_its_device(void)
>>>>  	return kvm_register_device_ops(&kvm_arm_vgic_its_ops,
>>>>  				       KVM_DEV_TYPE_ARM_VGIC_ITS);
>>>>  }
>>>> +
>>>> +/*
>>>> + * Registers all ITSes with the kvm_io_bus framework.
>>>> + * To follow the existing VGIC initialization sequence, this has to be
>>>> + * done as late as possible, just before the first VCPU runs.
>>>> + */
>>>> +int vgic_register_its_iodevs(struct kvm *kvm)
>>>> +{
>>>> +	struct kvm_device *dev;
>>>> +	int ret = 0;
>>>> +
>>>> +	mutex_lock(&kvm->devices_lock);
>>>> +
>>>> +	list_for_each_entry(dev, &kvm->devices, vm_node) {
>>>> +		if (dev->ops != &kvm_arm_vgic_its_ops)
>>>> +			continue;
>>>> +
>>>> +		ret = vgic_register_its_iodev(kvm, dev->private);
>>>> +		if (ret)
>>>> +			break;
>>>> +	}
>>>> +
>>>> +	if (ret) {
>>>> +		/* Iterate backwards to roll back previous registrations. */
>>>> +		for (dev = list_prev_entry(dev, vm_node);
>>>> +		     &dev->vm_node != &kvm->devices;
>>>> +		     dev = list_prev_entry(dev, vm_node)) {
>>>> +			struct vgic_its *its = dev->private;
>>>> +
>>>> +			if (dev->ops != &kvm_arm_vgic_its_ops)
>>>> +				continue;
>>>> +
>>>> +			kvm_io_bus_unregister_dev(kvm, KVM_MMIO_BUS,
>>>> +						  &its->iodev.dev);
>>>> +		}
>>>> +	}
>>>
>>> is the unregister really necessary?
>>
>> I was wondering the same, but we do it for the GICv3 redistributors as
>> well (though that was introduced by the same stupid author).
>> That being said I would be too happy to remove both these dodgy routines
>> if we agree that a failure will ultimately lead to a VM teardown and is
>> thus not needed.
> 
> Well to me this will lead to a kvm_vcpu_ioctl/KVM_RUN failure. Then the
> unregistration only happens in kvm_destroy_vm/kvm_io_bus_destroy and
> this calls iodevice destructor ops which is not implemented for our
> device so I don't think this can be removed right now.
hum no I mixed things I think: The destructor is needed if we want to
remove our io-dev explicit deallocation in vgic and vits. Anyway this
could be more elegant than what we have now. I can take this in charge
if confirmed.

sorry for the noise

Eric
> 
> We shall implement this destructor ops first. In the past I attempted to
> use the destructor (early ages of new vgic) but this crashed. I think
> this crash should not happen anymore after:
> e6e3b5a64e5f15ebd569118a9af16bd4165cbd1a
> 
> I tested the new version with a qemu integration looking similar to
> other vgic init:
> 
> Tested-by: Eric Auger <eric.auger@redhat.com>
> 
> Cheers
> 
> Eric
> 
> 
>>
>> Cheers,
>> Andre.
>>
>>>
>>>> +
>>>> +	mutex_unlock(&kvm->devices_lock);
>>>> +	return ret;
>>>> +}
>>>> diff --git a/virt/kvm/arm/vgic/vgic-v3.c b/virt/kvm/arm/vgic/vgic-v3.c
>>>> index 0506543..f0d9b2b 100644
>>>> --- a/virt/kvm/arm/vgic/vgic-v3.c
>>>> +++ b/virt/kvm/arm/vgic/vgic-v3.c
>>>> @@ -289,6 +289,12 @@ int vgic_v3_map_resources(struct kvm *kvm)
>>>>  		goto out;
>>>>  	}
>>>>  
>>>> +	ret = vgic_register_its_iodevs(kvm);
>>>> +	if (ret) {
>>>> +		kvm_err("Unable to register VGIC ITS MMIO regions\n");
>>>> +		goto out;
>>>> +	}
>>>> +
>>>>  	dist->ready = true;
>>>>  
>>>>  out:
>>>> diff --git a/virt/kvm/arm/vgic/vgic.h b/virt/kvm/arm/vgic/vgic.h
>>>> index 1d8e21d..6c4625c 100644
>>>> --- a/virt/kvm/arm/vgic/vgic.h
>>>> +++ b/virt/kvm/arm/vgic/vgic.h
>>>> @@ -84,6 +84,7 @@ void vgic_v3_enable(struct kvm_vcpu *vcpu);
>>>>  int vgic_v3_probe(const struct gic_kvm_info *info);
>>>>  int vgic_v3_map_resources(struct kvm *kvm);
>>>>  int vgic_register_redist_iodevs(struct kvm *kvm, gpa_t dist_base_address);
>>>> +int vgic_register_its_iodevs(struct kvm *kvm);
>>>>  bool vgic_has_its(struct kvm *kvm);
>>>>  int kvm_vgic_register_its_device(void);
>>>>  void vgic_enable_lpis(struct kvm_vcpu *vcpu);
>>>> @@ -140,6 +141,11 @@ static inline int vgic_register_redist_iodevs(struct kvm *kvm,
>>>>  	return -ENODEV;
>>>>  }
>>>>  
>>>> +static inline int vgic_register_its_iodevs(struct kvm *kvm)
>>>> +{
>>>> +	return -ENODEV;
>>>> +}
>>>> +
>>>>  static inline bool vgic_has_its(struct kvm *kvm)
>>>>  {
>>>>  	return false;
>>>> -- 
>>>> 2.9.0
>>>>
>>>
>>> Otherwise this looks good to me.
>>>
>>> Can someone provide a tested-by ?
>>>
>>> Thanks,
>>> -Christoffer
>>>
>>
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