On Mon, 31 Oct 2016 14:35:05 +0800
Jike Song <jike.song@xxxxxxxxx> wrote:
Patch title is "set/put" but there is no "put".
> A vfio_group may be or may not be attached to a KVM instance,
> if it is, the user of vfio_group might also want to know which
> KVM instance it is attached to, to utilize features provided
> by KVM. In VFIO there are already external APIs for KVM to
> get/put the vfio_group, by extending that, KVM can set or clear
> itself to/from the vfio_group, for external users to use.
>
> Signed-off-by: Jike Song <jike.song@xxxxxxxxx>
> ---
> drivers/vfio/vfio.c | 30 ++++++++++++++++++++++++++++++
> include/linux/vfio.h | 4 ++++
> 2 files changed, 34 insertions(+)
>
> diff --git a/drivers/vfio/vfio.c b/drivers/vfio/vfio.c
> index e3e58e3..41611cc 100644
> --- a/drivers/vfio/vfio.c
> +++ b/drivers/vfio/vfio.c
> @@ -34,6 +34,7 @@
> #include <linux/uaccess.h>
> #include <linux/vfio.h>
> #include <linux/wait.h>
> +#include <linux/kvm_host.h>
>
> #define DRIVER_VERSION "0.3"
> #define DRIVER_AUTHOR "Alex Williamson <alex.williamson@xxxxxxxxxx>"
> @@ -86,6 +87,10 @@ struct vfio_group {
> struct mutex unbound_lock;
> atomic_t opened;
> bool noiommu;
> + struct {
> + struct kvm *kvm;
> + struct mutex lock;
> + } udata;
> };
>
> struct vfio_device {
> @@ -333,6 +338,7 @@ static struct vfio_group *vfio_create_group(struct iommu_group *iommu_group)
> mutex_init(&group->device_lock);
> INIT_LIST_HEAD(&group->unbound_list);
> mutex_init(&group->unbound_lock);
> + mutex_init(&group->udata.lock);
> atomic_set(&group->container_users, 0);
> atomic_set(&group->opened, 0);
> group->iommu_group = iommu_group;
> @@ -1739,6 +1745,30 @@ long vfio_external_check_extension(struct vfio_group *group, unsigned long arg)
> }
> EXPORT_SYMBOL_GPL(vfio_external_check_extension);
>
> +void vfio_group_set_kvm(struct vfio_group *group, struct kvm *kvm)
> +{
> + mutex_lock(&group->udata.lock);
> + group->udata.kvm = kvm;
> + mutex_unlock(&group->udata.lock);
> +}
> +EXPORT_SYMBOL_GPL(vfio_group_set_kvm);
> +
> +struct kvm *vfio_group_get_kvm(struct vfio_group *group)
> +{
> + struct kvm *kvm = NULL;
Unnecessary initialization.
> +
> + mutex_lock(&group->udata.lock);
> +
> + kvm = group->udata.kvm;
> + if (kvm)
> + kvm_get_kvm(kvm);
> +
> + mutex_unlock(&group->udata.lock);
> +
> + return kvm;
> +}
> +EXPORT_SYMBOL_GPL(vfio_group_get_kvm);
> +
How are kvm references acquired through vfio_group_get_kvm() ever
released? Can the reference become invalid? The caller may still hold
a kvm references, but couldn't the group be detached from one kvm
instance and re-attached to another? This seems like an ad-hoc
reference that doesn't impose any usage semantics on the caller or
release mechanism. Thanks,
Alex
> /**
> * Sub-module support
> */
> diff --git a/include/linux/vfio.h b/include/linux/vfio.h
> index ad9b857..3abd690 100644
> --- a/include/linux/vfio.h
> +++ b/include/linux/vfio.h
> @@ -95,6 +95,10 @@ extern long vfio_external_check_extension(struct vfio_group *group,
> extern struct vfio_group *vfio_group_get_from_dev(struct device *dev);
> extern void vfio_group_put(struct vfio_group *group);
>
> +struct kvm;
> +extern void vfio_group_set_kvm(struct vfio_group *group, struct kvm *kvm);
> +extern struct kvm *vfio_group_get_kvm(struct vfio_group *group);
> +
> /*
> * Sub-module helpers
> */
--
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