[PATCH V4 03/18] iommu/ioasid: Add a separate function for detach data
From: Jacob Pan <hidden>
Date: 2021-02-28 06:35:22
Also in:
linux-iommu, lkml
Subsystem:
intel iommu (vt-d), iommu subsystem, the rest · Maintainers:
David Woodhouse, Lu Baolu, Joerg Roedel, Will Deacon, Linus Torvalds
IOASID private data can be cleared by ioasid_attach_data() with a NULL data pointer. A common use case is for a caller to free the data afterward. ioasid_attach_data() calls synchronize_rcu() before return such that free data can be sure without outstanding readers. However, since synchronize_rcu() may sleep, ioasid_attach_data() cannot be used under spinlocks. This patch adds ioasid_detach_data() as a separate API where synchronize_rcu() is called only in this case. ioasid_attach_data() can then be used under spinlocks. In addition, this change makes the API symmetrical. Signed-off-by: Jacob Pan <jacob.jun.pan-VuQAYsv1563Yd54FQh9/CA@public.gmane.org> --- drivers/iommu/intel/svm.c | 4 +-- drivers/iommu/ioasid.c | 54 +++++++++++++++++++++++++++++++-------- include/linux/ioasid.h | 5 +++- 3 files changed, 50 insertions(+), 13 deletions(-)
diff --git a/drivers/iommu/intel/svm.c b/drivers/iommu/intel/svm.c
index 0053df9edffc..68372a7eb8b5 100644
--- a/drivers/iommu/intel/svm.c
+++ b/drivers/iommu/intel/svm.c@@ -425,7 +425,7 @@ int intel_svm_bind_gpasid(struct iommu_domain *domain, struct device *dev, list_add_rcu(&sdev->list, &svm->devs); out: if (!IS_ERR_OR_NULL(svm) && list_empty(&svm->devs)) { - ioasid_attach_data(data->hpasid, NULL); + ioasid_detach_data(data->hpasid); kfree(svm); }
@@ -468,7 +468,7 @@ int intel_svm_unbind_gpasid(struct device *dev, u32 pasid) * the unbind, IOMMU driver will get notified * and perform cleanup. */ - ioasid_attach_data(pasid, NULL); + ioasid_detach_data(pasid); kfree(svm); } }
diff --git a/drivers/iommu/ioasid.c b/drivers/iommu/ioasid.c
index eeadf4586e0a..4eb9b3dd1b85 100644
--- a/drivers/iommu/ioasid.c
+++ b/drivers/iommu/ioasid.c@@ -273,23 +273,57 @@ int ioasid_attach_data(ioasid_t ioasid, void *data) spin_lock(&ioasid_allocator_lock); ioasid_data = xa_load(&active_allocator->xa, ioasid); - if (ioasid_data) - rcu_assign_pointer(ioasid_data->private, data); - else + + if (!ioasid_data) { ret = -ENOENT; - spin_unlock(&ioasid_allocator_lock); + goto done_unlock; + } - /* - * Wait for readers to stop accessing the old private data, so the - * caller can free it. - */ - if (!ret) - synchronize_rcu(); + if (ioasid_data->private) { + ret = -EBUSY; + goto done_unlock; + } + rcu_assign_pointer(ioasid_data->private, data); + +done_unlock: + spin_unlock(&ioasid_allocator_lock); return ret; } EXPORT_SYMBOL_GPL(ioasid_attach_data); +/** + * ioasid_detach_data - Clear the private data of an ioasid + * + * @ioasid: the IOASIDD to clear private data + */ +void ioasid_detach_data(ioasid_t ioasid) +{ + struct ioasid_data *ioasid_data; + + spin_lock(&ioasid_allocator_lock); + ioasid_data = xa_load(&active_allocator->xa, ioasid); + + if (!ioasid_data) { + pr_warn("IOASID %u not found to detach data from\n", ioasid); + goto done_unlock; + } + + if (ioasid_data->private) { + rcu_assign_pointer(ioasid_data->private, NULL); + goto done_unlock; + } + +done_unlock: + spin_unlock(&ioasid_allocator_lock); + /* + * Wait for readers to stop accessing the old private data, + * so the caller can free it. + */ + synchronize_rcu(); +} +EXPORT_SYMBOL_GPL(ioasid_detach_data); + /** * ioasid_alloc - Allocate an IOASID * @set: the IOASID set
diff --git a/include/linux/ioasid.h b/include/linux/ioasid.h
index 60ea279802b8..f6e705f832f0 100644
--- a/include/linux/ioasid.h
+++ b/include/linux/ioasid.h@@ -41,7 +41,7 @@ void *ioasid_find(struct ioasid_set *set, ioasid_t ioasid, int ioasid_register_allocator(struct ioasid_allocator_ops *allocator); void ioasid_unregister_allocator(struct ioasid_allocator_ops *allocator); int ioasid_attach_data(ioasid_t ioasid, void *data); - +void ioasid_detach_data(ioasid_t ioasid); #else /* !CONFIG_IOASID */ static inline ioasid_t ioasid_alloc(struct ioasid_set *set, ioasid_t min, ioasid_t max, void *private)
@@ -78,5 +78,8 @@ static inline int ioasid_attach_data(ioasid_t ioasid, void *data) return -ENOTSUPP; } +static inline void ioasid_detach_data(ioasid_t ioasid) +{ +} #endif /* CONFIG_IOASID */ #endif /* __LINUX_IOASID_H */
--
2.25.1