On Tue, 22 Nov 2016 19:05:16 +0530
Kirti Wankhede <kwankhede@xxxxxxxxxx> wrote:
> On 11/22/2016 11:39 AM, Jike Song wrote:
> > Beyond vfio_iommu events, users might also be interested in
> > vfio_group events. For example, if a vfio_group is used along
> > with Qemu/KVM, whenever kvm pointer is set to/cleared from the
> > vfio_group, users could be notified.
> >
> > Currently only VFIO_GROUP_NOTIFY_SET_KVM supported.
> >
> > Cc: Alex Williamson <alex.williamson@xxxxxxxxxx>
> > Cc: Kirti Wankhede <kwankhede@xxxxxxxxxx>
> > Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx>
> > Cc: Xiao Guangrong <guangrong.xiao@xxxxxxxxxxxxxxx>
> > Signed-off-by: Jike Song <jike.song@xxxxxxxxx>
> > ---
> > drivers/vfio/vfio.c | 82 ++++++++++++++++++++++++++++++++++++++++++++++++++++
> > include/linux/vfio.h | 6 ++++
> > 2 files changed, 88 insertions(+)
> >
> > diff --git a/drivers/vfio/vfio.c b/drivers/vfio/vfio.c
> > index 493bbad..3ab5edb 100644
> > --- a/drivers/vfio/vfio.c
> > +++ b/drivers/vfio/vfio.c
> > @@ -86,6 +86,8 @@ struct vfio_group {
> > struct mutex unbound_lock;
> > atomic_t opened;
> > bool noiommu;
> > + struct kvm *kvm;
> > + struct blocking_notifier_head notifier;
> > };
> >
> > struct vfio_device {
> > @@ -339,6 +341,7 @@ static struct vfio_group *vfio_create_group(struct iommu_group *iommu_group)
> > #ifdef CONFIG_VFIO_NOIOMMU
> > group->noiommu = (iommu_group_get_iommudata(iommu_group) == &noiommu);
> > #endif
> > + BLOCKING_INIT_NOTIFIER_HEAD(&group->notifier);
> >
> > group->nb.notifier_call = vfio_iommu_group_notifier;
> >
> > @@ -1581,6 +1584,9 @@ static int vfio_group_fops_release(struct inode *inode, struct file *filep)
> >
> > filep->private_data = NULL;
> >
> > + /* Any user didn't unregister? */
> > + WARN_ON(group->notifier.head);
> > +
> > vfio_group_try_dissolve_container(group);
> >
> > atomic_dec(&group->opened);
> > @@ -2069,6 +2075,76 @@ static int vfio_unregister_iommu_notifier(struct vfio_group *group,
> > return ret;
> > }
> >
> > +void vfio_group_set_kvm(struct vfio_group *group, struct kvm *kvm)
> > +{
> > + group->kvm = kvm;
> > + blocking_notifier_call_chain(&group->notifier,
> > + VFIO_GROUP_NOTIFY_SET_KVM, kvm);
> > +}
> > +EXPORT_SYMBOL_GPL(vfio_group_set_kvm);
> > +
> > +static int vfio_register_group_notifier(struct vfio_group *group,
> > + unsigned long *events,
> > + struct notifier_block *nb)
> > +{
> > + struct vfio_container *container;
> > + int ret;
> > + bool set_kvm = false;
> > +
> > + if (*events & VFIO_GROUP_NOTIFY_SET_KVM)
> > + set_kvm = true;
> > +
> > + /* clear known events */
> > + *events &= ~VFIO_GROUP_NOTIFY_SET_KVM;
> > +
> > + /* refuse to continue if still events remaining */
> > + if (*events)
> > + return -EINVAL;
> > +
> > + ret = vfio_group_add_container_user(group);
> > + if (ret)
> > + return -EINVAL;
> > +
> > + container = group->container;
> > + down_read(&container->group_lock);
> > +
> > + ret = blocking_notifier_chain_register(&group->notifier, nb);
> > +
> > + /*
> > + * The attaching of kvm and vfio_group might already happen, so
> > + * here we replay once upon registration.
> > + */
> > + if (!ret && set_kvm && group->kvm)
> > + blocking_notifier_call_chain(&group->notifier,
> > + VFIO_GROUP_NOTIFY_SET_KVM, group->kvm);
> > +
> > + up_read(&container->group_lock);
> > + vfio_group_try_dissolve_container(group);
> > +
> > + return ret;
> > +}
> > +
> > +static int vfio_unregister_group_notifier(struct vfio_group *group,
> > + struct notifier_block *nb)
> > +{
> > + struct vfio_container *container;
> > + int ret;
> > +
> > + ret = vfio_group_add_container_user(group);
> > + if (ret)
> > + return -EINVAL;
> > +
> > + container = group->container;
> > + down_read(&container->group_lock);
> > +
> > + ret = blocking_notifier_chain_unregister(&group->notifier, nb);
> > +
> > + up_read(&container->group_lock);
> > + vfio_group_try_dissolve_container(group);
> > +
> > + return ret;
> > +}
> > +
> > int vfio_register_notifier(struct device *dev, vfio_notify_type_t type,
> > unsigned long *events,
> > struct notifier_block *nb)
> > @@ -2087,6 +2163,9 @@ int vfio_register_notifier(struct device *dev, vfio_notify_type_t type,
> > case VFIO_IOMMU_NOTIFY:
> > ret = vfio_register_iommu_notifier(group, events, nb);
> > break;
> > + case VFIO_GROUP_NOTIFY:
> > + ret = vfio_register_group_notifier(group, events, nb);
> > + break;
> > default:
> > ret = -EINVAL;
> > }
> > @@ -2113,6 +2192,9 @@ int vfio_unregister_notifier(struct device *dev, vfio_notify_type_t type,
> > case VFIO_IOMMU_NOTIFY:
> > ret = vfio_unregister_iommu_notifier(group, nb);
> > break;
> > + case VFIO_GROUP_NOTIFY:
> > + ret = vfio_unregister_group_notifier(group, nb);
> > + break;
> > default:
> > ret = -EINVAL;
> > }
> > diff --git a/include/linux/vfio.h b/include/linux/vfio.h
> > index 6f3ff31..5d46e3c 100644
> > --- a/include/linux/vfio.h
> > +++ b/include/linux/vfio.h
> > @@ -119,11 +119,17 @@ extern int vfio_unregister_notifier(struct device *dev,
> > /* each type has independent events */
> > enum vfio_notify_type {
> > VFIO_IOMMU_NOTIFY = (__force vfio_notify_type_t)0,
> > + VFIO_GROUP_NOTIFY = (__force vfio_notify_type_t)1,
> > };
> >
> > /* events for VFIO_IOMMU_NOTIFY */
> > #define VFIO_IOMMU_NOTIFY_DMA_UNMAP BIT(0)
> >
> > +/* events for VFIO_GROUP_NOTIFY */
> > +#define VFIO_GROUP_NOTIFY_SET_KVM BIT(0)
> > +
> > +struct kvm;
> > +extern void vfio_group_set_kvm(struct vfio_group *group, struct kvm *kvm);
> >
>
> If I understand correctly, notifier for backend iommu driver and
> notifier for group should be registered with different notifier blocks,
> as per your current implementation:
>
> unsigned long iommu_event = VFIO_IOMMU_NOTIFY_DMA_UNMAP;
> struct notifier_block iommu_nb;
>
> iommu_nb.notifier_call = vfio_iommu_notifier_cb;
> vfio_register_notifier(dev, VFIO_IOMMU_NOTIFY, &iommu_event, &iommu_nb);
>
>
> unsigned long group_event = VFIO_GROUP_NOTIFY_SET_KVM;
> struct notifier_block group_nb;
>
> group_nb.notifier_call = vfio_group_notifier_cb;
> vfio_register_notifier(dev, VFIO_GROUP_NOTIFY, &group_event, &group_nb);
>
> Then what is the use of having 'events' bitmask as input argument?
>
> Its clear that caller should set:
> - VFIO_IOMMU_NOTIFY_DMA_UNMAP when vfio_notify_type_t is VFIO_IOMMU_NOTIFY
> - VFIO_GROUP_NOTIFY_SET_KVM when vfio_notify_type_t is VFIO_GROUP_NOTIFY
>
> Notifier action could be a integer as earlier and indexing of action
> would be different for both notifiers.
>
> Then caller don't have to sent event bitmask, for caller it would look like:
>
> struct notifier_block iommu_nb;
>
> iommu_nb.notifier_call = vfio_iommu_notifier_cb;
> vfio_register_notifier(dev, VFIO_IOMMU_NOTIFY, &iommu_nb);
>
>
> struct notifier_block group_nb;
>
> group_nb.notifier_call = vfio_group_notifier_cb;
> vfio_register_notifier(dev, VFIO_GROUP_NOTIFY, &group_nb);
If we did that then we'd effectively need to add a new notifier any
time we want a new signal because the vendor driver would have no
ability to query the notifications available. For instance, say we
added VFIO_IOMMU_NOTIFY_SET_FOO and a vendor driver was dependent on
that and would either refuse to work or would take a backup path if
that notification isn't available. How could it operate in your
proposal? By passing a bitmask of events, the vendor driver can
specify the set of required events and see which event signaling is
unavailable. The purpose of using a bitmask and passing the set of
required bits on registration is to support future expansion. Thanks,
Alex
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