Subject: [RFC v2 8/9] KVM: KVM-VFIO: generic KVM_DEV_VFIO_DEVICE command and IRQ forwarding control

From: [email-masked] (Eric Auger)
Date: Thu, 11 Sep 2014 14:04:39 +0200

On 09/11/2014 07:05 AM, Alex Williamson wrote:
> On Thu, 2014-09-11 at 05:10 +0200, Christoffer Dall wrote:
>> On Mon, Sep 01, 2014 at 02:52:47PM +0200, Eric Auger wrote:
>>> This patch introduces a new KVM_DEV_VFIO_DEVICE attribute.
>>>
>>> This is a new control channel which enables KVM to cooperate with
>>> viable VFIO devices.
>>>
>>> The kvm-vfio device now holds a list of devices (kvm_vfio_device)
>>> in addition to a list of groups (kvm_vfio_group). The new
>>> infrastructure enables to check the validity of the VFIO device
>>> file descriptor, get and hold a reference to it.
>>>
>>> The first concrete implemented command is IRQ forward control:
>>> KVM_DEV_VFIO_DEVICE_FORWARD_IRQ, KVM_DEV_VFIO_DEVICE_UNFORWARD_IRQ.
>>>
>>> It consists in programing the VFIO driver and KVM in a consistent manner
>>> so that an optimized IRQ injection/completion is set up. Each
>>> kvm_vfio_device holds a list of forwarded IRQ. When putting a
>>> kvm_vfio_device, the implementation makes sure the forwarded IRQs
>>> are set again in the normal handling state (non forwarded).
>>
>> 'putting a kvm_vfio_device' sounds to like you're golf'ing :)
>>
>> When a kvm_vfio_device is released?
>>
>>>
>>> The forwarding programmming is architecture specific, embodied by the
>>> kvm_arch_set_fwd_state function. Its implementation is given in a
>>> separate patch file.
>>
>> I would drop the last sentence and instead indicate that this is handled
>> properly when the architecture does not support such a feature.
>>
>>>
>>> The forwarding control modality is enabled by the
>>> __KVM_HAVE_ARCH_KVM_VFIO_FORWARD define.
>>>
>>> Signed-off-by: Eric Auger <[email-masked]>
>>>
>>> ---
>>>
>>> v1 -> v2:
>>> - __KVM_HAVE_ARCH_KVM_VFIO renamed into __KVM_HAVE_ARCH_KVM_VFIO_FORWARD
>>> - original patch file separated into 2 parts: generic part moved in vfio.c
>>>   and ARM specific part(kvm_arch_set_fwd_state)
>>> ---
>>>  include/linux/kvm_host.h |  27 +++
>>>  virt/kvm/vfio.c          | 452 ++++++++++++++++++++++++++++++++++++++++++++++-
>>>  2 files changed, 477 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
>>> index a4c33b3..24350dc 100644
>>> --- a/include/linux/kvm_host.h
>>> +++ b/include/linux/kvm_host.h
>>> @@ -1065,6 +1065,21 @@ struct kvm_device_ops {
>>>  		      unsigned long arg);
>>>  };
>>>  
>>> +enum kvm_fwd_irq_action {
>>> +	KVM_VFIO_IRQ_SET_FORWARD,
>>> +	KVM_VFIO_IRQ_SET_NORMAL,
>>> +	KVM_VFIO_IRQ_CLEANUP,
>>
>> This is KVM internal API, so it would probably be good to document this.
>> Especially the CLEANUP bit worries me, see below.
> 
> This also doesn't match the user API, which is simply FORWARD/UNFORWARD.
Hi Alex,

will change that.
> Extra states worry me too.

I tried to explained the 2 motivations behind. Please let me know if it
makes sense.
> 
>>> +};
>>> +
>>> +/* internal structure describing a forwarded IRQ */
>>> +struct kvm_fwd_irq {
>>> +	struct list_head link;
>>
>> this list entry is local to the kvm vfio device, right? that means you
>> probably want a struct with just the below fields, and then have a
>> containing struct in the generic device file, private to it's logic.
> 
> Yes, this is part of the abstraction problem.
OK will fix that.
> 
>>> +	__u32 index; /* platform device irq index */
> 
> This is a vfio_device irq_index, but vfio_devices support indexes and
> sub-indexes.  At this level the API should match vfio, not the specifics
> of platform devices not supporting sub-index.
I will add sub-indexes then.
> 
>>> +	__u32 hwirq; /*physical IRQ */
>>> +	__u32 gsi; /* virtual IRQ */
>>> +	struct kvm_vcpu *vcpu; /* vcpu to inject into*/
> 
> Not sure I understand why vcpu is necessary.
vcpu is used when providing the physical IRQ/virtual IRQ mapping to the
virtual GIC. I can remove it from and add a vcpu struct * param to
kvm_arch_set_fwd_state if you prefer.

  Also I see a 'get' in the code below, but not a 'put'.
Sorry I do not understand your comment here? What 'get' do you mention?
> 
>>> +};
>>> +
>>>  void kvm_device_get(struct kvm_device *dev);
>>>  void kvm_device_put(struct kvm_device *dev);
>>>  struct kvm_device *kvm_device_from_filp(struct file *filp);
>>> @@ -1075,6 +1090,18 @@ extern struct kvm_device_ops kvm_vfio_ops;
>>>  extern struct kvm_device_ops kvm_arm_vgic_v2_ops;
>>>  extern struct kvm_device_ops kvm_flic_ops;
>>>  
>>> +#ifdef __KVM_HAVE_ARCH_KVM_VFIO_FORWARD
>>> +int kvm_arch_set_fwd_state(struct kvm_fwd_irq *pfwd,
>>
>> what's the 'p' in pfwd?
> 
> p is for pointer?
yes it was ;-)
> 
>>> +			   enum kvm_fwd_irq_action action);
>>> +
>>> +#else
>>> +static inline int kvm_arch_set_fwd_state(struct kvm_fwd_irq *pfwd,
>>> +					 enum kvm_fwd_irq_action action)
>>> +{
>>> +	return 0;
>>> +}
>>> +#endif
>>> +
>>>  #ifdef CONFIG_HAVE_KVM_CPU_RELAX_INTERCEPT
>>>  
>>>  static inline void kvm_vcpu_set_in_spin_loop(struct kvm_vcpu *vcpu, bool val)
>>> diff --git a/virt/kvm/vfio.c b/virt/kvm/vfio.c
>>> index 76dc7a1..e4a81c4 100644
>>> --- a/virt/kvm/vfio.c
>>> +++ b/virt/kvm/vfio.c
>>> @@ -18,14 +18,24 @@
>>>  #include <linux/slab.h>
>>>  #include <linux/uaccess.h>
>>>  #include <linux/vfio.h>
>>> +#include <linux/platform_device.h>
>>>  
>>>  struct kvm_vfio_group {
>>>  	struct list_head node;
>>>  	struct vfio_group *vfio_group;
>>>  };
>>>  
>>> +struct kvm_vfio_device {
>>> +	struct list_head node;
>>> +	struct vfio_device *vfio_device;
>>> +	/* list of forwarded IRQs for that VFIO device */
>>> +	struct list_head fwd_irq_list;
>>> +	int fd;
>>> +};
>>> +
>>>  struct kvm_vfio {
>>>  	struct list_head group_list;
>>> +	struct list_head device_list;
>>>  	struct mutex lock;
>>>  	bool noncoherent;
>>>  };
>>> @@ -246,12 +256,441 @@ static int kvm_vfio_set_group(struct kvm_device *dev, long attr, u64 arg)
>>>  	return -ENXIO;
>>>  }
>>>  
>>> +/**
>>> + * get_vfio_device - returns the vfio-device corresponding to this fd
>>> + * @fd:fd of the vfio platform device
>>> + *
>>> + * checks it is a vfio device
>>> + * increment its ref counter
>>
>> why the short lines?  Just write this out in proper English.
>>
>>> + */
>>> +static struct vfio_device *kvm_vfio_get_vfio_device(int fd)
>>> +{
>>> +	struct fd f;
>>> +	struct vfio_device *vdev;
>>> +
>>> +	f = fdget(fd);
>>> +	if (!f.file)
>>> +		return NULL;
>>> +	vdev = kvm_vfio_device_get_external_user(f.file);
>>> +	fdput(f);
>>> +	return vdev;
>>> +}
>>> +
>>> +/**
>>> + * put_vfio_device: put the vfio platform device
>>> + * @vdev: vfio_device to put
>>> + *
>>> + * decrement the ref counter
>>> + */
>>> +static void kvm_vfio_put_vfio_device(struct vfio_device *vdev)
>>> +{
>>> +	kvm_vfio_device_put_external_user(vdev);
>>> +}
>>> +
>>> +/**
>>> + * kvm_vfio_find_device - look for the device in the assigned
>>> + * device list
>>> + * @kv: the kvm-vfio device
>>> + * @vdev: the vfio_device to look for
>>> + *
>>> + * returns the associated kvm_vfio_device if the device is known,
>>> + * meaning at least 1 IRQ is forwarded for this device.
>>> + * in the device is not registered, returns NULL.
>>> + */
> 
> Why are we talking about forwarded IRQs already, this is a simple lookup
> function, who knows what other users it will have in the future.
I will correct
> 
>>
>> are these functions meant to be exported?  Otherwise they should be
>> static, and the documentation on these simple list iteration wrappers
>> seems like overkill imho.
>>
>>> +struct kvm_vfio_device *kvm_vfio_find_device(struct kvm_vfio *kv,
>>> +					     struct vfio_device *vdev)
>>> +{
>>> +	struct kvm_vfio_device *kvm_vdev_iter;
>>> +
>>> +	list_for_each_entry(kvm_vdev_iter, &kv->device_list, node) {
>>> +		if (kvm_vdev_iter->vfio_device == vdev)
>>> +			return kvm_vdev_iter;
>>> +	}
>>> +	return NULL;
>>> +}
>>> +
>>> +/**
>>> + * kvm_vfio_find_irq - look for a an irq in the device IRQ list
>>> + * @kvm_vdev: the kvm_vfio_device
>>> + * @irq_index: irq index
>>> + *
>>> + * returns the forwarded irq struct if it exists, NULL in the negative
>>> + */
>>> +struct kvm_fwd_irq *kvm_vfio_find_irq(struct kvm_vfio_device *kvm_vdev,
>>> +				      int irq_index)
> 
> +sub-index
OK
> 
> probably important to note on both of these that they need to be called
> with kv->lock
OK
> 
>>> +{
>>> +	struct kvm_fwd_irq *fwd_irq_iter;
>>> +
>>> +	list_for_each_entry(fwd_irq_iter, &kvm_vdev->fwd_irq_list, link) {
>>> +		if (fwd_irq_iter->index == irq_index)
>>> +			return fwd_irq_iter;
>>> +	}
>>> +	return NULL;
>>> +}
>>> +
>>> +/**
>>> + * validate_forward - checks whether forwarding a given IRQ is meaningful
>>> + * @vdev:  vfio_device the IRQ belongs to
>>> + * @fwd_irq: user struct containing the irq_index to forward
>>> + * @kvm_vdev: if a forwarded IRQ already exists for that VFIO device,
>>> + * kvm_vfio_device that holds it
>>> + * @hwirq: irq numberthe irq index corresponds to
>>> + *
>>> + * checks the vfio-device is a platform vfio device
>>> + * checks the irq_index corresponds to an actual hwirq and
>>> + * checks this hwirq is not already forwarded
>>> + * returns < 0 on following errors:
>>> + * not a platform device, bad irq index, already forwarded
>>> + */
>>> +static int kvm_vfio_validate_forward(struct kvm_vfio *kv,
>>> +			    struct vfio_device *vdev,
>>> +			    struct kvm_arch_forwarded_irq *fwd_irq,
>>> +			    struct kvm_vfio_device **kvm_vdev,
>>> +			    int *hwirq)
>>> +{
>>> +	struct device *dev = kvm_vfio_external_base_device(vdev);
>>> +	struct platform_device *platdev;
>>> +
>>> +	*hwirq = -1;
>>> +	*kvm_vdev = NULL;
>>> +	if (strcmp(dev->bus->name, "platform") == 0) {
> 
> Should be testing dev->bus_type == &platform_bus_type, and ideally
> creating a dev_is_platform() macro to make that even cleaner.
OK
> 
> However, we're being sort of sneaky here that we're actually doing
> something platform device specific here.  Why?  Don't we just need to
> make sure that kvm-vfio doesn't have any record of this forward
> (-EEXIST) and let the platform device code error out later for this
> case?
After having answered to Christoffer's comments, I think I should check
whether the IRQ is not already mapped at VGIC level. In that case I
would need to split the validate function into 2 parts:
- generic part only checks the vfio_device/irq_index is not already
recorded. I do not need the hwirq for that.
- arm specific part checks no GIC mapping does exist (need the hwirq)

Would it be OK for both of you?
> 
>>> +		platdev = to_platform_device(dev);
>>> +		*hwirq = platform_get_irq(platdev, fwd_irq->index);
>>> +		if (*hwirq < 0) {
>>> +			kvm_err("%s incorrect index\n", __func__);
>>> +			return -EINVAL;
>>> +		}
>>> +	} else {
>>> +		kvm_err("%s not a platform device\n", __func__);
>>> +		return -EINVAL;
>>> +	}
>>
>> need some spaceing here, also, I would turn this around, first check if
>> the strcmp fails, and then error out, then do you next check etc., to
>> avoid so many nested statements.
>>
>>> +	/* is a ref to this device already owned by the KVM-VFIO device? */
>>
>> this comment is not particularly helpful in its current form, it would
>> be helpful if you specified that we're checking whether that particular
>> device/irq combo is already registered.
>>
>>> +	*kvm_vdev = kvm_vfio_find_device(kv, vdev);
>>> +	if (*kvm_vdev) {
>>> +		if (kvm_vfio_find_irq(*kvm_vdev, fwd_irq->index)) {
>>> +			kvm_err("%s irq %d already forwarded\n",
>>> +				__func__, *hwirq);
> 
> Why didn't we do this first?
see above comment
> 
>> don't flood the kernel log because of a user error, just allocate an
>> error code for this purpose and document it in the ABI, -EEXIST or
>> something.
>>
>>> +			return -EINVAL;
>>> +		}
>>> +	}
>>> +	return 0;
>>> +}
>>> +
>>> +/**
>>> + * validate_unforward: check a deassignment is meaningful
>>> + * @kv: the kvm_vfio device
>>> + * @vdev: the vfio_device whose irq to deassign belongs to
>>> + * @fwd_irq: the user struct that contains the fd and irq_index of the irq
>>> + * @kvm_vdev: the kvm_vfio_device the forwarded irq belongs to, if
>>> + * it exists
>>> + *
>>> + * returns 0 if the provided irq effectively is forwarded
>>> + * (a ref to this vfio_device is hold and this irq belongs to
>>                                     held
>>> + * the forwarded irq of this device)
>>> + * returns -EINVAL in the negative
>>
>>                ENOENT should be returned if you don't have an entry.
>> 	       EINVAL could be used if you supply an fd that isn't a
>> 	       VFIO device file descriptor, for example.  Again,
>> 	       consider documenting all this in the API.
>>
>>> + */
>>> +static int kvm_vfio_validate_unforward(struct kvm_vfio *kv,
>>> +			      struct vfio_device *vdev,
>>> +			      struct kvm_arch_forwarded_irq *fwd_irq,
>>> +			      struct kvm_vfio_device **kvm_vdev)
>>> +{
>>> +	struct kvm_fwd_irq *pfwd;
>>> +
>>> +	*kvm_vdev = kvm_vfio_find_device(kv, vdev);
>>> +	if (!kvm_vdev) {
>>> +		kvm_err("%s no forwarded irq for this device\n", __func__);
>>
>> don't flood the kernel log
>>
>>> +		return -EINVAL;
>>> +	}
>>> +	pfwd = kvm_vfio_find_irq(*kvm_vdev, fwd_irq->index);
>>> +	if (!pfwd) {
>>> +		kvm_err("%s irq %d is not forwarded\n", __func__, fwd_irq->fd);
>>
>>> +		return -EINVAL;
>>
>> same here
I do not understand. With current functions I need to first retrieve the
device and then iterate on IRQs of that device.
>>
>>> +	}
>>> +	return 0;
>>> +}
>>> +
>>> +/**
>>> + * kvm_vfio_forward - set a forwarded IRQ
>>> + * @kdev: the kvm device
>>> + * @vdev: the vfio device the IRQ belongs to
>>> + * @fwd_irq: the user struct containing the irq_index and guest irq
>>> + * @must_put: tells the caller whether the vfio_device must be put after
>>> + * the call (ref must be released in case a ref onto this device was
>>> + * already hold or in case of new device and failure)
>>> + *
>>> + * validate the injection, activate forward and store the information
>>       Validate
>>> + * about which irq and which device is concerned so that on deassign or
>>> + * kvm-vfio destruction everuthing can be cleaned up.
>>                            everything
>>
>> I'm not sure I understand this explanation.  Do we have concerned
>> devices?
>>
>> I think you want to say something along the lines of: If userspace passed
>> a valid vfio device and irq handle and the architecture supports
>> forwarding this combination, register the vfio_device and irq
>> combination in the ....
>>
>>> + */
>>> +static int kvm_vfio_forward(struct kvm_device *kdev,
>>> +			    struct vfio_device *vdev,
>>> +			    struct kvm_arch_forwarded_irq *fwd_irq,
>>> +			    bool *must_put)
>>> +{
>>> +	int ret;
>>> +	struct kvm_fwd_irq *pfwd = NULL;
>>> +	struct kvm_vfio_device *kvm_vdev = NULL;
>>> +	struct kvm_vfio *kv = kdev->private;
>>> +	int hwirq;
>>> +
>>> +	*must_put = true;
>>> +	ret = kvm_vfio_validate_forward(kv, vdev, fwd_irq,
>>> +					&kvm_vdev, &hwirq);
>>> +	if (ret < 0)
>>> +		return -EINVAL;
>>> +
>>> +	pfwd = kzalloc(sizeof(*pfwd), GFP_KERNEL);
>>
>> seems a bit pointless to zero-out the memory if you're setting all
>> fields below.
>>
>>> +	if (!pfwd)
>>> +		return -ENOMEM;
>>> +	pfwd->index = fwd_irq->index;
>>> +	pfwd->gsi = fwd_irq->gsi;
>>> +	pfwd->hwirq = hwirq;
>>> +	pfwd->vcpu = kvm_get_vcpu(kdev->kvm, 0);
>>> +	ret = kvm_arch_set_fwd_state(pfwd, KVM_VFIO_IRQ_SET_FORWARD);
>>> +	if (ret < 0) {
>>> +		kvm_arch_set_fwd_state(pfwd, KVM_VFIO_IRQ_CLEANUP);
>>
>> this whole thing feels incredibly broken to me.  Setting a forward
>> should either work or not work, not something in between that leaves
>> something to be cleaned up.  Why this two-stage thingy here?
> 
> Yep, I agree.  I also don't see the point of the validate function, just
> open code it here and push the platform_get_irq test into
> kvm_arch_set_fwd_state.  kvm-vfio doesn't care about the hwirq.
> 
>>> +		kfree(pfwd);
>>
>> probably want to move your free-and-return-error to the end of the
>> function.
>>
>>> +		return ret;
>>> +	}
>>> +
>>> +	if (!kvm_vdev) {
>>> +		/* create & insert the new device and keep the ref */
>>> +		kvm_vdev = kzalloc(sizeof(*kvm_vdev), GFP_KERNEL);
>>
>> again, no need for zeroing out the memory.
> 
> I think you also want to allocate this before you setup the forward so
> you can eliminate any complicated teardown later.
ok
> 
>>> +		if (!kvm_vdev) {
>>> +			kvm_arch_set_fwd_state(pfwd, false);
> 
> false?  The function takes an enum.
Thanks for identifying that bug.
> 
>>> +			kfree(pfwd);
>>> +			return -ENOMEM;
>>> +		}
>>> +
>>> +		kvm_vdev->vfio_device = vdev;
>>> +		kvm_vdev->fd = fwd_irq->fd;
>>> +		INIT_LIST_HEAD(&kvm_vdev->fwd_irq_list);
>>> +		list_add(&kvm_vdev->node, &kv->device_list);
>>> +		/*
>>> +		 * the only case where we keep the ref:
>>> +		 * new device and forward setting successful
>>> +		 */
>>> +		*must_put = false;
>>> +	}
>>> +
>>> +	list_add(&pfwd->link, &kvm_vdev->fwd_irq_list);
>>> +
>>> +	kvm_debug("forwarding set for fd=%d, hwirq=%d, gsi=%d\n",
>>> +	fwd_irq->fd, hwirq, fwd_irq->gsi);
>>
>> please indent this to align with the opening parenthesis.
>>
>>> +
>>> +	return 0;
>>> +}
>>> +
>>> +/**
>>> + * remove_assigned_device - put a given device from the list
>>
>> this isn't a 'put', at least not *just* a put.
>>
>>> + * @kv: the kvm-vfio device
>>> + * @vdev: the vfio-device to remove
>>> + *
>>> + * change the state of all forwarded IRQs, free the forwarded IRQ list,
>>> + * remove the corresponding kvm_vfio_device from the assigned device
>>> + * list.
>>> + * returns true if the device could be removed, false in the negative
>>> + */
>>> +bool remove_assigned_device(struct kvm_vfio *kv,
>>> +			    struct vfio_device *vdev)
>>> +{
>>> +	struct kvm_vfio_device *kvm_vdev_iter, *tmp_vdev;
>>> +	struct kvm_fwd_irq *fwd_irq_iter, *tmp_irq;
>>> +	bool removed = false;
>>> +	int ret;
>>> +
>>> +	list_for_each_entry_safe(kvm_vdev_iter, tmp_vdev,
>>> +				 &kv->device_list, node) {
>>> +		if (kvm_vdev_iter->vfio_device == vdev) {
>>> +			/* loop on all its forwarded IRQ */
>>> +			list_for_each_entry_safe(fwd_irq_iter, tmp_irq,
>>> +						 &kvm_vdev_iter->fwd_irq_list,
>>> +						 link) {
>>
>> hmm, seems this function is only called when you have no more forwarded
>> IRQs, so isn't all of this completely dead (and unnecessary) code?
>>
>>> +				ret = kvm_arch_set_fwd_state(fwd_irq_iter,
>>> +						KVM_VFIO_IRQ_SET_NORMAL);
>>> +				if (ret < 0)
>>> +					return ret;
>>
>> you're returning an error code to a bool function, which means you'll
>> return true when there was an error.  Is this your intention? ;)
>>
>> if we have an error here, this would be a very very bad situation wouldn't it?
>>
>>> +				list_del(&fwd_irq_iter->link);
>>> +				kfree(fwd_irq_iter);
>>> +			}
>>> +			/* all IRQs could be deassigned */
>>> +			list_del(&kvm_vdev_iter->node);
>>> +			kvm_vfio_device_put_external_user(
>>> +				kvm_vdev_iter->vfio_device);
>>> +			kfree(kvm_vdev_iter);
>>> +			removed = true;
>>> +			break;
>>> +		}
>>> +	}
>>> +	return removed;
>>> +}
>>> +
>>> +
>>> +/**
>>> + * remove_fwd_irq - remove a forwarded irq
>>> + *
>>> + * @kv: kvm-vfio device
>>> + * kvm_vdev: the kvm_vfio_device the IRQ belongs to
>>> + * irq_index: the index of the IRQ
>>> + *
>>> + * change the forwarded state of the IRQ, remove the IRQ from
>>> + * the device forwarded IRQ list. In case it is the last one,
>>> + * put the device
>>> + */
>>> +int remove_fwd_irq(struct kvm_vfio *kv,
>>> +		   struct kvm_vfio_device *kvm_vdev,
>>> +		   int irq_index)
>>> +{
>>> +	struct kvm_fwd_irq *fwd_irq_iter, *tmp_irq;
>>> +	int ret = -1;
>>> +
>>> +	list_for_each_entry_safe(fwd_irq_iter, tmp_irq,
>>> +				 &kvm_vdev->fwd_irq_list, link) {
>>
>> hmmm, you can only forward one irq for a specific device once, right?
>> And you already have a lookup function, so why not call that, and then
>> remove it?
>>
>> I'm confused.

> 
> Me too, this and the previous function need some more consideration.
understood
> 
>>> +		if (fwd_irq_iter->index == irq_index) {
>>> +			ret = kvm_arch_set_fwd_state(fwd_irq_iter,
>>> +						KVM_VFIO_IRQ_SET_NORMAL);
>>> +			if (ret < 0)
>>> +				break;
>>> +			list_del(&fwd_irq_iter->link);
>>> +			kfree(fwd_irq_iter);
>>> +			ret = 0;
>>> +			break;
>>> +		}
>>> +	}
>>> +	if (list_empty(&kvm_vdev->fwd_irq_list))
>>> +		remove_assigned_device(kv, kvm_vdev->vfio_device);
>>> +
>>> +	return ret;
>>> +}
>>> +
>>> +/**
>>> + * kvm_vfio_unforward - remove a forwarded IRQ
>>> + * @kdev: the kvm device
>>> + * @vdev: the vfio_device
>>> + * @fwd_irq: user struct
>>> + * after checking this IRQ effectively is forwarded, change its state,
>>> + * remove it from the corresponding kvm_vfio_device list
>>> + */
>>> +static int kvm_vfio_unforward(struct kvm_device *kdev,
>>> +				     struct vfio_device *vdev,
>>> +				     struct kvm_arch_forwarded_irq *fwd_irq)
>>> +{
>>> +	struct kvm_vfio *kv = kdev->private;
>>> +	struct kvm_vfio_device *kvm_vdev;
>>> +	int ret;
>>> +
>>> +	ret = kvm_vfio_validate_unforward(kv, vdev, fwd_irq, &kvm_vdev);
>>> +	if (ret < 0)
>>> +		return -EINVAL;
>>
>> why do you override the return value?  Propagate it.
>>
>>> +
>>> +	ret = remove_fwd_irq(kv, kvm_vdev, fwd_irq->index);
>>> +	if (ret < 0)
>>> +		kvm_err("%s fail unforwarding (fd=%d, index=%d)\n",
>>> +			__func__, fwd_irq->fd, fwd_irq->index);
>>> +	else
>>> +		kvm_debug("%s unforwarding IRQ (fd=%d, index=%d)\n",
>>> +			  __func__, fwd_irq->fd, fwd_irq->index);
>>
>> again with the kernel log here.
>>
>>
>>
>>> +	return ret;
>>> +}
>>> +
>>> +
>>> +
>>> +
>>> +/**
>>> + * kvm_vfio_set_device - the top function for interracting with a vfio
>>
>>                                 top?             interacting
>>
>>> + * device
>>> + */
>>
>> probably just skip this comment
>>
>>> +static int kvm_vfio_set_device(struct kvm_device *kdev, long attr, u64 arg)
>>> +{
>>> +	struct kvm_vfio *kv = kdev->private;
>>> +	struct vfio_device *vdev;
>>> +	struct kvm_arch_forwarded_irq fwd_irq; /* user struct */
>>> +	int32_t __user *argp = (int32_t __user *)(unsigned long)arg;
>>> +
>>> +	switch (attr) {
>>> +#ifdef __KVM_HAVE_ARCH_KVM_VFIO_FORWARD
>>> +	case KVM_DEV_VFIO_DEVICE_FORWARD_IRQ:{
>>> +		bool must_put;
>>> +		int ret;
>>> +
>>> +		if (copy_from_user(&fwd_irq, argp, sizeof(fwd_irq)))
>>> +			return -EFAULT;
>>> +		vdev = kvm_vfio_get_vfio_device(fwd_irq.fd);
>>> +		if (IS_ERR(vdev))
>>> +			return PTR_ERR(vdev);
>>
>> seems like this whole block of code is replicated below, needs
>> refactoring.
>>
>>> +		mutex_lock(&kv->lock);
>>> +		ret = kvm_vfio_forward(kdev, vdev, &fwd_irq, &must_put);
>>> +		if (must_put)
>>> +			kvm_vfio_put_vfio_device(vdev);
>>
>> this must_put looks plain weird.  I think you want to balance your
>> get/put's always; can't you just get an extra reference in
>> kvm_vfio_forward() ?
> 
> Yeah, this is very broken.  Every forwarded IRQ should hold a reference
> to the vfio_device.  Every unforward should drop a reference.  Trying to
> maintain a single reference is a non-goal.
OK will do that.
> 
>>
>>> +		mutex_unlock(&kv->lock);
>>> +		return ret;
>>> +		}
>>> +	case KVM_DEV_VFIO_DEVICE_UNFORWARD_IRQ: {
>>> +		int ret;
>>> +
>>> +		if (copy_from_user(&fwd_irq, argp, sizeof(fwd_irq)))
>>> +			return -EFAULT;
>>> +		vdev = kvm_vfio_get_vfio_device(fwd_irq.fd);
>>> +		if (IS_ERR(vdev))
>>> +			return PTR_ERR(vdev);
>>> +
>>> +		kvm_vfio_device_put_external_user(vdev);
>>
>> you're dropping the reference to the device but referencing it in your
>> unfoward call below?
>>
>>> +		mutex_lock(&kv->lock);
>>> +		ret = kvm_vfio_unforward(kdev, vdev, &fwd_irq);
>>> +		mutex_unlock(&kv->lock);
>>> +		return ret;
>>> +	}
>>> +#endif
>>> +	default:
>>> +		return -ENXIO;
>>> +	}
>>> +}
>>> +
>>> +/**
>>> + * kvm_vfio_put_all_devices - cancel forwarded IRQs and put all devices
>>> + * @kv: kvm-vfio device
>>> + *
>>> + * loop on all got devices and their associated forwarded IRQs
>>
>> 'loop on all got' ?
>>
>> Restore the non-forwarded state for all registered devices and ...
>>
>>> + * restore the non forwarded state, remove IRQs and their devices from
>>> + * the respective list, put the vfio platform devices
>>> + *
>>> + * When this function is called, the vcpu already are destroyed. No
>>                                     the VPUCs are already destroyed.
>>> + * vgic manipulation can happen hence the KVM_VFIO_IRQ_CLEANUP
>>> + * kvm_arch_set_fwd_state action
>>
>> this last bit didn't make any sense to me.  Also, why are we referring
>> to the vgic in generic code?
>>
>>> + */
>>> +int kvm_vfio_put_all_devices(struct kvm_vfio *kv)
>>> +{
>>> +	struct kvm_fwd_irq *fwd_irq_iter, *tmp_irq;
>>> +	struct kvm_vfio_device *kvm_vdev_iter, *tmp_vdev;
>>> +
>>> +	/* loop on all the assigned devices */
>>
>> unnecessary comment
>>
>>> +	list_for_each_entry_safe(kvm_vdev_iter, tmp_vdev,
>>> +				 &kv->device_list, node) {
>>> +
>>> +		/* loop on all its forwarded IRQ */
>>
>> same
>>
>>> +		list_for_each_entry_safe(fwd_irq_iter, tmp_irq,
>>> +					 &kvm_vdev_iter->fwd_irq_list, link) {
>>> +			kvm_arch_set_fwd_state(fwd_irq_iter,
>>> +						KVM_VFIO_IRQ_CLEANUP);
>>> +			list_del(&fwd_irq_iter->link);
>>> +			kfree(fwd_irq_iter);
>>> +		}
> 
> 
> Ugh, how many of these cleanup functions do we need?
will simplify!

Thanks

Best Regards

Eric
> 
>>> +		list_del(&kvm_vdev_iter->node);
>>> +		kvm_vfio_device_put_external_user(kvm_vdev_iter->vfio_device);
>>> +		kfree(kvm_vdev_iter);
>>> +	}
>>> +	return 0;
>>> +}
>>> +
>>> +
>>>  static int kvm_vfio_set_attr(struct kvm_device *dev,
>>>  			     struct kvm_device_attr *attr)
>>>  {
>>>  	switch (attr->group) {
>>>  	case KVM_DEV_VFIO_GROUP:
>>>  		return kvm_vfio_set_group(dev, attr->attr, attr->addr);
>>> +	case KVM_DEV_VFIO_DEVICE:
>>> +		return kvm_vfio_set_device(dev, attr->attr, attr->addr);
>>>  	}
>>>  
>>>  	return -ENXIO;
>>> @@ -267,10 +706,17 @@ static int kvm_vfio_has_attr(struct kvm_device *dev,
>>>  		case KVM_DEV_VFIO_GROUP_DEL:
>>>  			return 0;
>>>  		}
>>> -
>>>  		break;
>>> +#ifdef __KVM_HAVE_ARCH_KVM_VFIO_FORWARD
>>> +	case KVM_DEV_VFIO_DEVICE:
>>> +		switch (attr->attr) {
>>> +		case KVM_DEV_VFIO_DEVICE_FORWARD_IRQ:
>>> +		case KVM_DEV_VFIO_DEVICE_UNFORWARD_IRQ:
>>> +			return 0;
>>> +		}
>>> +		break;
>>> +#endif
>>>  	}
>>> -
>>>  	return -ENXIO;
>>>  }
>>>  
>>> @@ -284,6 +730,7 @@ static void kvm_vfio_destroy(struct kvm_device *dev)
>>>  		list_del(&kvg->node);
>>>  		kfree(kvg);
>>>  	}
>>> +	kvm_vfio_put_all_devices(kv);
>>>  
>>>  	kvm_vfio_update_coherency(dev);
>>>  
>>> @@ -306,6 +753,7 @@ static int kvm_vfio_create(struct kvm_device *dev, u32 type)
>>>  		return -ENOMEM;
>>>  
>>>  	INIT_LIST_HEAD(&kv->group_list);
>>> +	INIT_LIST_HEAD(&kv->device_list);
>>>  	mutex_init(&kv->lock);
>>>  
>>>  	dev->private = kv;
>>> -- 
>>> 1.9.1
>>>
> 
> 
>