Commit f794eec8 authored by Jason Gunthorpe's avatar Jason Gunthorpe
Browse files

vfio: Simplify vfio_create_group() 

The vfio.group_lock is now only used to serialize vfio_group creation and
destruction, we don't need a micro-optimization of searching, unlocking,
then allocating and searching again. Just hold the lock the whole time.

Grabbed from:
https://lore.kernel.org/kvm/20220922152338.2a2238fe.alex.williamson@redhat.com/

Link: https://lore.kernel.org/r/20221201145535.589687-2-yi.l.liu@intel.com


Reviewed-by: default avatarKevin Tian <kevin.tian@intel.com>
Reviewed-by: default avatarJason Gunthorpe <jgg@nvidia.com>
Tested-by: default avatarLixiao Yang <lixiao.yang@intel.com>
Tested-by: default avatarYu He <yu.he@intel.com>
Signed-off-by: default avatarJason Gunthorpe <jgg@nvidia.com>
Signed-off-by: default avatarAlex Williamson <alex.williamson@redhat.com>
Signed-off-by: default avatarYi Liu <yi.l.liu@intel.com>
parent 90337f52

drivers/vfio/vfio_main.c

+10 −23
Original line number Diff line number Diff line
@@ -143,10 +143,12 @@ EXPORT_SYMBOL_GPL(vfio_device_set_open_count); 
 * Group objects - create, release, get, put, search

 */

static struct vfio_group *

__vfio_group_get_from_iommu(struct iommu_group *iommu_group)

vfio_group_get_from_iommu(struct iommu_group *iommu_group)

{

	struct vfio_group *group;



	lockdep_assert_held(&vfio.group_lock);



	/*

	 * group->iommu_group from the vfio.group_list cannot be NULL

	 * under the vfio.group_lock.
@@ -160,17 +162,6 @@ __vfio_group_get_from_iommu(struct iommu_group *iommu_group) 
	return NULL;

}



static struct vfio_group *

vfio_group_get_from_iommu(struct iommu_group *iommu_group)

{

	struct vfio_group *group;



	mutex_lock(&vfio.group_lock);

	group = __vfio_group_get_from_iommu(iommu_group);

	mutex_unlock(&vfio.group_lock);

	return group;

}



static void vfio_group_release(struct device *dev)

{

	struct vfio_group *group = container_of(dev, struct vfio_group, dev);
@@ -225,6 +216,8 @@ static struct vfio_group *vfio_create_group(struct iommu_group *iommu_group, 
	struct vfio_group *ret;

	int err;



	lockdep_assert_held(&vfio.group_lock);



	group = vfio_group_alloc(iommu_group, type);

	if (IS_ERR(group))

		return group;
@@ -237,26 +230,16 @@ static struct vfio_group *vfio_create_group(struct iommu_group *iommu_group, 
		goto err_put;

	}



	mutex_lock(&vfio.group_lock);



	/* Did we race creating this group? */

	ret = __vfio_group_get_from_iommu(iommu_group);

	if (ret)

		goto err_unlock;



	err = cdev_device_add(&group->cdev, &group->dev);

	if (err) {

		ret = ERR_PTR(err);

		goto err_unlock;

		goto err_put;

	}



	list_add(&group->vfio_next, &vfio.group_list);



	mutex_unlock(&vfio.group_lock);

	return group;



err_unlock:

	mutex_unlock(&vfio.group_lock);

err_put:

	put_device(&group->dev);

	return ret;
@@ -467,7 +450,9 @@ static struct vfio_group *vfio_noiommu_group_alloc(struct device *dev, 
	if (ret)

		goto out_put_group;



	mutex_lock(&vfio.group_lock);

	group = vfio_create_group(iommu_group, type);

	mutex_unlock(&vfio.group_lock);

	if (IS_ERR(group)) {

		ret = PTR_ERR(group);

		goto out_remove_device;
@@ -516,9 +501,11 @@ static struct vfio_group *vfio_group_find_or_alloc(struct device *dev) 
		return ERR_PTR(-EINVAL);

	}



	mutex_lock(&vfio.group_lock);

	group = vfio_group_get_from_iommu(iommu_group);

	if (!group)

		group = vfio_create_group(iommu_group, VFIO_IOMMU);

	mutex_unlock(&vfio.group_lock);



	/* The vfio_group holds a reference to the iommu_group */

	iommu_group_put(iommu_group);