RE: [PATCH v3 7/8] KVM: kvm-vfio: generic forwarding control

["Wu, Feng" <feng.wu@intel.com>]

> -----Original Message-----
> From: Eric Auger [mailto:eric.auger@linaro.org]
> Sent: Monday, November 24, 2014 2:36 AM
> To: eric.auger@st.com; eric.auger@linaro.org; christoffer.dall@linaro.org;
> marc.zyngier@arm.com; linux-arm-kernel@lists.infradead.org;
> kvmarm@lists.cs.columbia.edu; kvm@vger.kernel.org;
> alex.williamson@redhat.com; joel.schopp@amd.com;
> kim.phillips@freescale.com; paulus@samba.org; gleb@kernel.org;
> pbonzini@redhat.com; agraf@suse.de
> Cc: linux-kernel@vger.kernel.org; patches@linaro.org; will.deacon@arm.com;
> a.motakis@virtualopensystems.com; a.rigo@virtualopensystems.com;
> john.liuli@huawei.com; ming.lei@canonical.com; Wu, Feng
> Subject: [PATCH v3 7/8] KVM: kvm-vfio: generic forwarding control
> 
> This patch introduces a new KVM_DEV_VFIO_DEVICE group.
> 
> This is a new control channel which enables KVM to cooperate with
> viable VFIO devices.
> 
> Functions are introduced to check the validity of a VFIO device
> file descriptor, increment/decrement the ref counter of the VFIO
> device.
> 
> The patch introduces 2 attributes for this new device group:
> KVM_DEV_VFIO_DEVICE_FORWARD_IRQ,
> KVM_DEV_VFIO_DEVICE_UNFORWARD_IRQ.
> Their purpose is to turn a VFIO device IRQ into a forwarded IRQ and
> unset respectively unset the feature.
> 
> The VFIO device stores a list of registered forwarded IRQs. The reference
> counter of the device is incremented each time a new IRQ is forwarded.
> Reference counter is decremented when the IRQ forwarding is unset.
> 
> The forwarding programmming is architecture specific, implemented in
> kvm_arch_set_fwd_state function. Architecture specific implementation is
> enabled when __KVM_HAVE_ARCH_KVM_VFIO_FORWARD is set. When not
> set those
> functions are void.
> 
> Signed-off-by: Eric Auger <eric.auger@linaro.org>
> 
> ---
> 
> v2 -> v3:
> - add API comments in kvm_host.h
> - improve the commit message
> - create a private kvm_vfio_fwd_irq struct
> - fwd_irq_action replaced by a bool and removal of VFIO_IRQ_CLEANUP. This
>   latter action will be handled in vgic.
> - add a vfio_device handle argument to kvm_arch_set_fwd_state. The goal is
>   to move platform specific stuff in architecture specific code.
> - kvm_arch_set_fwd_state renamed into kvm_arch_vfio_set_forward
> - increment the ref counter each time we do an IRQ forwarding and decrement
>   this latter each time one IRQ forward is unset. Simplifies the whole
>   ref counting.
> - simplification of list handling: create, search, removal
> 
> 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 |  28 ++++++
>  virt/kvm/vfio.c          | 249
> ++++++++++++++++++++++++++++++++++++++++++++++-
>  2 files changed, 274 insertions(+), 3 deletions(-)
> 
> diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
> index ea53b04..0b9659d 100644
> --- a/include/linux/kvm_host.h
> +++ b/include/linux/kvm_host.h
> @@ -1076,6 +1076,15 @@ struct kvm_device_ops {
>  		      unsigned long arg);
>  };
> 
> +/* internal self-contained structure describing a forwarded IRQ */
> +struct kvm_fwd_irq {
> +	struct kvm *kvm; /* VM to inject the GSI into */
> +	struct vfio_device *vdev; /* vfio device the IRQ belongs to */
> +	__u32 index; /* VFIO device IRQ index */
> +	__u32 subindex; /* VFIO device IRQ subindex */
> +	__u32 gsi; /* gsi, ie. virtual IRQ number */
> +};
> +
>  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);
> @@ -1085,6 +1094,25 @@ void kvm_unregister_device_ops(u32 type);
>  extern struct kvm_device_ops kvm_mpic_ops;
>  extern struct kvm_device_ops kvm_xics_ops;
> 
> +#ifdef __KVM_HAVE_ARCH_KVM_VFIO_FORWARD
> +/**
> + * kvm_arch_vfio_set_forward - changes the forwarded state of an IRQ
> + *
> + * @fwd_irq: handle to the forwarded irq struct
> + * @forward: true means forwarded, false means not forwarded
> + * returns 0 on success, < 0 on failure
> + */
> +int kvm_arch_vfio_set_forward(struct kvm_fwd_irq *fwd_irq,
> +			      bool forward);
> +
> +#else
> +static inline int kvm_arch_vfio_set_forward(struct kvm_fwd_irq *fwd_irq,
> +					    bool forward)
> +{
> +	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 6f0cc34..af178bb 100644
> --- a/virt/kvm/vfio.c
> +++ b/virt/kvm/vfio.c
> @@ -25,8 +25,16 @@ struct kvm_vfio_group {
>  	struct vfio_group *vfio_group;
>  };
> 
> +/* private linkable kvm_fwd_irq struct */
> +struct kvm_vfio_fwd_irq_node {
> +	struct list_head link;
> +	struct kvm_fwd_irq fwd_irq;
> +};
> +
>  struct kvm_vfio {
>  	struct list_head group_list;
> +	/* list of registered VFIO forwarded IRQs */
> +	struct list_head fwd_node_list;
>  	struct mutex lock;
>  	bool noncoherent;
>  };
> @@ -247,12 +255,239 @@ static int kvm_vfio_set_group(struct kvm_device
> *dev, long attr, u64 arg)
>  	return -ENXIO;
>  }
> 
> +/**
> + * kvm_vfio_get_vfio_device - Returns a handle to a vfio-device
> + *
> + * Checks it is a valid vfio device and increments its reference counter
> + * @fd: file descriptor of the vfio platform device
> + */
> +static struct vfio_device *kvm_vfio_get_vfio_device(int fd)
> +{
> +	struct fd f = fdget(fd);
> +	struct vfio_device *vdev;
> +
> +	if (!f.file)
> +		return NULL;
> +	vdev = kvm_vfio_device_get_external_user(f.file);
> +	fdput(f);
> +	return vdev;
> +}
> +
> +/**
> + * kvm_vfio_put_vfio_device: decrements the reference counter of the
> + * vfio platform * device
> + *
> + * @vdev: vfio_device handle to release
> + */
> +static void kvm_vfio_put_vfio_device(struct vfio_device *vdev)
> +{
> +	kvm_vfio_device_put_external_user(vdev);
> +}
> +
> +/**
> + * kvm_vfio_find_fwd_irq - checks whether a forwarded IRQ already is
> + * registered in the list of forwarded IRQs
> + *
> + * @kv: handle to the kvm-vfio device
> + * @fwd: handle to the forwarded irq struct
> + * In the positive returns the handle to its node in the kvm-vfio
> + * forwarded IRQ list, returns NULL otherwise.
> + * Must be called with kv->lock hold.
> + */
> +static struct kvm_vfio_fwd_irq_node *kvm_vfio_find_fwd_irq(
> +				struct kvm_vfio *kv,
> +				struct kvm_fwd_irq *fwd)
> +{
> +	struct kvm_vfio_fwd_irq_node *node;
> +
> +	list_for_each_entry(node, &kv->fwd_node_list, link) {
> +		if ((node->fwd_irq.index == fwd->index) &&
> +		    (node->fwd_irq.subindex == fwd->subindex) &&
> +		    (node->fwd_irq.vdev == fwd->vdev))
> +			return node;
> +	}
> +	return NULL;
> +}
> +/**
> + * kvm_vfio_register_fwd_irq - Allocates, populates and registers a
> + * forwarded IRQ
> + *
> + * @kv: handle to the kvm-vfio device
> + * @fwd: handle to the forwarded irq struct
> + * In case of success returns a handle to the new list node,
> + * NULL otherwise.
> + * Must be called with kv->lock hold.
> + */
> +static struct kvm_vfio_fwd_irq_node *kvm_vfio_register_fwd_irq(
> +				struct kvm_vfio *kv,
> +				struct kvm_fwd_irq *fwd)
> +{
> +	struct kvm_vfio_fwd_irq_node *node;
> +
> +	node = kmalloc(sizeof(*node), GFP_KERNEL);
> +	if (!node)
> +		return NULL;
> +
> +	node->fwd_irq = *fwd;
> +
> +	list_add(&node->link, &kv->fwd_node_list);
> +
> +	return node;
> +}
> +
> +/**
> + * kvm_vfio_unregister_fwd_irq - unregisters and frees a forwarded IRQ
> + *
> + * @node: handle to the node struct
> + * Must be called with kv->lock hold.
> + */
> +static void kvm_vfio_unregister_fwd_irq(struct kvm_vfio_fwd_irq_node
> *node)
> +{
> +	list_del(&node->link);
> +	kfree(node);
> +}
> +
> +/**
> + * kvm_vfio_set_forward - turns a VFIO device IRQ into a forwarded IRQ
> + * @kv: handle to the kvm-vfio device
> + * @fd: file descriptor of the vfio device the IRQ belongs to
> + * @fwd: handle to the forwarded irq struct
> + *
> + * Registers an IRQ as forwarded and calls the architecture specific
> + * implementation of set_forward. In case of operation failure, the IRQ
> + * is unregistered. In case of success, the vfio device ref counter is
> + * incremented.
> + */
> +static int kvm_vfio_set_forward(struct kvm_vfio *kv, int fd,
> +				struct kvm_fwd_irq *fwd)
> +{
> +	int ret;
> +	struct kvm_vfio_fwd_irq_node *node =
> +			kvm_vfio_find_fwd_irq(kv, fwd);
> +
> +	if (node)
> +		return -EINVAL;
> +	node = kvm_vfio_register_fwd_irq(kv, fwd);
> +	if (!node)
> +		return -ENOMEM;
> +	ret = kvm_arch_vfio_set_forward(fwd, true);
> +	if (ret < 0)  {
> +		kvm_vfio_unregister_fwd_irq(node);
> +		return ret;
> +	}
> +	/* increment the ref counter */
> +	kvm_vfio_get_vfio_device(fd);
> +	return ret;
> +}
> +
> +/**
> + * kvm_vfio_unset_forward - Sets a VFIO device IRQ as non forwarded
> + * @kv: handle to the kvm-vfio device
> + * @fwd: handle to the forwarded irq struct
> + *
> + * Calls the architecture specific implementation of set_forward and
> + * unregisters the IRQ from the forwarded IRQ list. Decrements the vfio
> + * device reference counter.
> + */
> +static int kvm_vfio_unset_forward(struct kvm_vfio *kv,
> +				  struct kvm_fwd_irq *fwd)
> +{
> +	int ret;
> +	struct kvm_vfio_fwd_irq_node *node =
> +			kvm_vfio_find_fwd_irq(kv, fwd);
> +	if (!node)
> +		return -EINVAL;
> +	ret = kvm_arch_vfio_set_forward(fwd, false);
> +	kvm_vfio_unregister_fwd_irq(node);
> +
> +	/* decrement the ref counter */
> +	kvm_vfio_put_vfio_device(fwd->vdev);
> +	return ret;
> +}
> +
> +static int kvm_vfio_control_irq_forward(struct kvm_device *kdev, long attr,
> +					int32_t __user *argp)
> +{
> +	struct kvm_arch_forwarded_irq user_fwd_irq;
> +	struct kvm_fwd_irq fwd;
> +	struct vfio_device *vdev;
> +	struct kvm_vfio *kv = kdev->private;
> +	int ret;
> +
> +	if (copy_from_user(&user_fwd_irq, argp, sizeof(user_fwd_irq)))
> +		return -EFAULT;
> +
> +	vdev = kvm_vfio_get_vfio_device(user_fwd_irq.fd);
> +	if (IS_ERR(vdev)) {
> +		ret = PTR_ERR(vdev);
> +		goto out;
> +	}
> +
> +	fwd.vdev =  vdev;
> +	fwd.kvm =  kdev->kvm;
> +	fwd.index = user_fwd_irq.index;
> +	fwd.subindex = user_fwd_irq.subindex;
> +	fwd.gsi = user_fwd_irq.gsi;
> +
> +	switch (attr) {
> +	case KVM_DEV_VFIO_DEVICE_FORWARD_IRQ:
> +		mutex_lock(&kv->lock);
> +		ret = kvm_vfio_set_forward(kv, user_fwd_irq.fd, &fwd);
> +		mutex_unlock(&kv->lock);
> +		break;
> +	case KVM_DEV_VFIO_DEVICE_UNFORWARD_IRQ:
> +		mutex_lock(&kv->lock);
> +		ret = kvm_vfio_unset_forward(kv, &fwd);
> +		mutex_unlock(&kv->lock);
> +		break;
> +	}
> +out:
> +	kvm_vfio_put_vfio_device(vdev);
> +	return ret;
> +}
> +
> +static int kvm_vfio_set_device(struct kvm_device *kdev, long attr, u64 arg)
> +{
> +	int32_t __user *argp = (int32_t __user *)(unsigned long)arg;
> +	int ret;
> +
> +	switch (attr) {
> +	case KVM_DEV_VFIO_DEVICE_FORWARD_IRQ:
> +	case KVM_DEV_VFIO_DEVICE_UNFORWARD_IRQ:
> +		ret = kvm_vfio_control_irq_forward(kdev, attr, argp);
> +		break;
> +	default:
> +		ret = -ENXIO;
> +	}
> +	return ret;
> +}
> +
> +/**
> + * kvm_vfio_clean_fwd_irq - Unset forwarding state of all
> + * registered forwarded IRQs and free their list nodes.
> + * @kv: kvm-vfio device
> + *
> + * Loop on all registered device/IRQ combos, reset the non forwarded state,
> + * void the lists and release the reference
> + */
> +static int kvm_vfio_clean_fwd_irq(struct kvm_vfio *kv)
> +{
> +	struct kvm_vfio_fwd_irq_node *node, *tmp;
> +
> +	list_for_each_entry_safe(node, tmp, &kv->fwd_node_list, link) {
> +		kvm_vfio_unset_forward(kv, &node->fwd_irq);
> +	}
> +	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;
> @@ -268,10 +503,17 @@ 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

Hi Eric,

Can you make the above code like this since group KVM_DEV_VFIO_DEVICE
will be used by posted interrupts as well, and new attributes will be added
in this group.

 +	case KVM_DEV_VFIO_DEVICE:
 +		switch (attr->attr) {
 +#ifdef __KVM_HAVE_ARCH_KVM_VFIO_FORWARD
 +		case KVM_DEV_VFIO_DEVICE_FORWARD_IRQ:
 +		case KVM_DEV_VFIO_DEVICE_UNFORWARD_IRQ:
 +			return 0;
 +#endif
 +		}
 +		break;

Thanks,
Feng


>  	}
> -
>  	return -ENXIO;
>  }
> 
> @@ -285,7 +527,7 @@ static void kvm_vfio_destroy(struct kvm_device *dev)
>  		list_del(&kvg->node);
>  		kfree(kvg);
>  	}
> -
> +	kvm_vfio_clean_fwd_irq(kv);
>  	kvm_vfio_update_coherency(dev);
> 
>  	kfree(kv);
> @@ -317,6 +559,7 @@ static int kvm_vfio_create(struct kvm_device *dev,
> u32 type)
>  		return -ENOMEM;
> 
>  	INIT_LIST_HEAD(&kv->group_list);
> +	INIT_LIST_HEAD(&kv->fwd_node_list);
>  	mutex_init(&kv->lock);
> 
>  	dev->private = kv;
> --
> 1.9.1