On 4/26/25 13:58, Nicolin Chen wrote:
For vIOMMU passing through HW resources to user space (VMs), add an mmap
infrastructure to map a region of hardware MMIO pages.
Maintain an mt_mmap per ictx for validations. To allow IOMMU drivers to
add and delete mmappable regions to/from the mt_mmap, add a pair of new
helpers: iommufd_ctx_alloc_mmap() and iommufd_ctx_free_mmap().
I am wondering why the dma_buf mechanism isn't used here, considering
that this also involves an export and import pattern.
Signed-off-by: Nicolin Chen <nicol...@nvidia.com>
---
drivers/iommu/iommufd/iommufd_private.h | 8 +++++
include/linux/iommufd.h | 15 ++++++++++
drivers/iommu/iommufd/driver.c | 39 +++++++++++++++++++++++++
drivers/iommu/iommufd/main.c | 39 +++++++++++++++++++++++++
4 files changed, 101 insertions(+)
diff --git a/drivers/iommu/iommufd/iommufd_private.h
b/drivers/iommu/iommufd/iommufd_private.h
index b974c207ae8a..db5b62ec4abb 100644
--- a/drivers/iommu/iommufd/iommufd_private.h
+++ b/drivers/iommu/iommufd/iommufd_private.h
@@ -7,6 +7,7 @@
#include <linux/iommu.h>
#include <linux/iommufd.h>
#include <linux/iova_bitmap.h>
+#include <linux/maple_tree.h>
#include <linux/rwsem.h>
#include <linux/uaccess.h>
#include <linux/xarray.h>
@@ -44,6 +45,7 @@ struct iommufd_ctx {
struct xarray groups;
wait_queue_head_t destroy_wait;
struct rw_semaphore ioas_creation_lock;
+ struct maple_tree mt_mmap;
struct mutex sw_msi_lock;
struct list_head sw_msi_list;
@@ -55,6 +57,12 @@ struct iommufd_ctx {
struct iommufd_ioas *vfio_ioas;
};
+/* Entry for iommufd_ctx::mt_mmap */
+struct iommufd_mmap {
+ unsigned long pfn_start;
+ unsigned long pfn_end;
+};
This structure is introduced to represent a mappable/mapped region,
right? It would be better to add comments specifying whether the start
and end are inclusive or exclusive.
+
/*
* The IOVA to PFN map. The map automatically copies the PFNs into multiple
* domains and permits sharing of PFNs between io_pagetable instances. This
diff --git a/include/linux/iommufd.h b/include/linux/iommufd.h
index 5dff154e8ce1..d63e2d91be0d 100644
--- a/include/linux/iommufd.h
+++ b/include/linux/iommufd.h
@@ -236,6 +236,9 @@ int iommufd_object_depend(struct iommufd_object
*obj_dependent,
struct iommufd_object *obj_depended);
void iommufd_object_undepend(struct iommufd_object *obj_dependent,
struct iommufd_object *obj_depended);
+int iommufd_ctx_alloc_mmap(struct iommufd_ctx *ictx, phys_addr_t base,
+ size_t size, unsigned long *immap_id);
+void iommufd_ctx_free_mmap(struct iommufd_ctx *ictx, unsigned long immap_id);
struct device *iommufd_viommu_find_dev(struct iommufd_viommu *viommu,
unsigned long vdev_id);
int iommufd_viommu_get_vdev_id(struct iommufd_viommu *viommu,
@@ -262,11 +265,23 @@ static inline int iommufd_object_depend(struct
iommufd_object *obj_dependent,
return -EOPNOTSUPP;
}
+static inline int iommufd_ctx_alloc_mmap(struct iommufd_ctx *ictx,
+ phys_addr_t base, size_t size,
+ unsigned long *immap_id)
+{
+ return -EOPNOTSUPP;
+}
+
static inline void iommufd_object_undepend(struct iommufd_object
*obj_dependent,
struct iommufd_object *obj_depended)
{
}
+static inline void iommufd_ctx_free_mmap(struct iommufd_ctx *ictx,
+ unsigned long immap_id)
+{
+}
+
static inline struct device *
iommufd_viommu_find_dev(struct iommufd_viommu *viommu, unsigned long vdev_id)
{
diff --git a/drivers/iommu/iommufd/driver.c b/drivers/iommu/iommufd/driver.c
index fb7f8fe40f95..c55336c580dc 100644
--- a/drivers/iommu/iommufd/driver.c
+++ b/drivers/iommu/iommufd/driver.c
@@ -78,6 +78,45 @@ void iommufd_object_undepend(struct iommufd_object
*obj_dependent,
}
EXPORT_SYMBOL_NS_GPL(iommufd_object_undepend, "IOMMUFD");
+/* Driver should report the output @immap_id to user space for mmap() syscall */
+int iommufd_ctx_alloc_mmap(struct iommufd_ctx *ictx, phys_addr_t base,
+ size_t size, unsigned long *immap_id)
+{
+ struct iommufd_mmap *immap;
+ int rc;
+
+ if (WARN_ON_ONCE(!immap_id))
+ return -EINVAL;
+ if (base & ~PAGE_MASK)
+ return -EINVAL;
Is it equal to PAGE_ALIGNED()?
+ if (!size || size & ~PAGE_MASK)
+ return -EINVAL;
+
+ immap = kzalloc(sizeof(*immap), GFP_KERNEL);
+ if (!immap)
+ return -ENOMEM;
+ immap->pfn_start = base >> PAGE_SHIFT;
+ immap->pfn_end = immap->pfn_start + (size >> PAGE_SHIFT) - 1;
+
+ rc = mtree_alloc_range(&ictx->mt_mmap, immap_id, immap, sizeof(immap),
+ 0, LONG_MAX >> PAGE_SHIFT, GFP_KERNEL);
+ if (rc < 0) {
+ kfree(immap);
+ return rc;
+ }
+
+ /* mmap() syscall will right-shift the immap_id to vma->vm_pgoff */
+ *immap_id <<= PAGE_SHIFT;
+ return 0;
+}
+EXPORT_SYMBOL_NS_GPL(iommufd_ctx_alloc_mmap, "IOMMUFD");
+
+void iommufd_ctx_free_mmap(struct iommufd_ctx *ictx, unsigned long immap_id)
+{
+ kfree(mtree_erase(&ictx->mt_mmap, immap_id >> PAGE_SHIFT));
MMIO lifecycle question: what happens if a region is removed from the
maple tree (and is therefore no longer mappable), but is still mapped
and in use by userspace?
+}
+EXPORT_SYMBOL_NS_GPL(iommufd_ctx_free_mmap, "IOMMUFD");
+
/* Caller should xa_lock(&viommu->vdevs) to protect the return value */
struct device *iommufd_viommu_find_dev(struct iommufd_viommu *viommu,
unsigned long vdev_id)
Thanks,
baolu
