From: Jason Gunthorpe <jgg@xxxxxxxxxx> 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@xxxxxxxxxx/ Signed-off-by: Jason Gunthorpe <jgg@xxxxxxxxxx> Signed-off-by: Alex Williamson <alex.williamson@xxxxxxxxxx> Signed-off-by: Yi Liu <yi.l.liu@xxxxxxxxx> --- drivers/vfio/vfio_main.c | 33 ++++++++++----------------------- 1 file changed, 10 insertions(+), 23 deletions(-) diff --git a/drivers/vfio/vfio_main.c b/drivers/vfio/vfio_main.c index ea07b46dcea2..02f344441ddf 100644 --- a/drivers/vfio/vfio_main.c +++ b/drivers/vfio/vfio_main.c @@ -146,10 +146,12 @@ 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. @@ -163,17 +165,6 @@ __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); @@ -228,6 +219,8 @@ 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; @@ -240,26 +233,16 @@ 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; @@ -470,7 +453,9 @@ 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; @@ -519,9 +504,11 @@ 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); -- 2.34.1
