iommufd: Data structure to provide IOVA to PFN mapping

This is the remainder of the IOAS data structure. Provide an object called
an io_pagetable that is composed of iopt_areas pointing at iopt_pages,
along with a list of iommu_domains that mirror the IOVA to PFN map.

At the top this is a simple interval tree of iopt_areas indicating the map
of IOVA to iopt_pages. An xarray keeps track of a list of domains. Based
on the attached domains there is a minimum alignment for areas (which may
be smaller than PAGE_SIZE), an interval tree of reserved IOVA that can't
be mapped and an IOVA of allowed IOVA that can always be mappable.

The concept of an 'access' refers to something like a VFIO mdev that is
accessing the IOVA and using a 'struct page *' for CPU based access.

Externally an API is provided that matches the requirements of the IOCTL
interface for map/unmap and domain attachment.

The API provides a 'copy' primitive to establish a new IOVA map in a
different IOAS from an existing mapping by re-using the iopt_pages. This
is the basic mechanism to provide single pinning.

This is designed to support a pre-registration flow where userspace would
setup an dummy IOAS with no domains, map in memory and then establish an
access to pin all PFNs into the xarray.

Copy can then be used to create new IOVA mappings in a different IOAS,
with iommu_domains attached. Upon copy the PFNs will be read out of the
xarray and mapped into the iommu_domains, avoiding any pin_user_pages()
overheads.

Link: https://lore.kernel.org/r/10-v6-a196d26f289e+11787-iommufd_jgg@nvidia.com
Tested-by: Nicolin Chen <nicolinc@nvidia.com>
Tested-by: Yi Liu <yi.l.liu@intel.com>
Tested-by: Lixiao Yang <lixiao.yang@intel.com>
Tested-by: Matthew Rosato <mjrosato@linux.ibm.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Signed-off-by: Yi Liu <yi.l.liu@intel.com>
Signed-off-by: Nicolin Chen <nicolinc@nvidia.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>

1 files changed, 55 insertions, 0 deletions

diff --git a/drivers/iommu/iommufd/io_pagetable.h b/drivers/iommu/iommufd/io_pagetable.h
index a2b724175057..2ee6942c3ef4 100644
--- a/drivers/iommu/iommufd/io_pagetable.h
+++ b/drivers/iommu/iommufd/io_pagetable.h
@@ -46,9 +46,19 @@ struct iopt_area {
 	unsigned int page_offset;
 	/* IOMMU_READ, IOMMU_WRITE, etc */
 	int iommu_prot;
+	bool prevent_access : 1;
 	unsigned int num_accesses;
 };
 
+struct iopt_allowed {
+	struct interval_tree_node node;
+};
+
+struct iopt_reserved {
+	struct interval_tree_node node;
+	void *owner;
+};
+
 int iopt_area_fill_domains(struct iopt_area *area, struct iopt_pages *pages);
 void iopt_area_unfill_domains(struct iopt_area *area, struct iopt_pages *pages);
 
@@ -83,6 +93,24 @@ static inline size_t iopt_area_length(struct iopt_area *area)
 	return (area->node.last - area->node.start) + 1;
 }
 
+/*
+ * Number of bytes from the start of the iopt_pages that the iova begins.
+ * iopt_area_start_byte() / PAGE_SIZE encodes the starting page index
+ * iopt_area_start_byte() % PAGE_SIZE encodes the offset within that page
+ */
+static inline unsigned long iopt_area_start_byte(struct iopt_area *area,
+						 unsigned long iova)
+{
+	return (iova - iopt_area_iova(area)) + area->page_offset +
+	       iopt_area_index(area) * PAGE_SIZE;
+}
+
+static inline unsigned long iopt_area_iova_to_index(struct iopt_area *area,
+						    unsigned long iova)
+{
+	return iopt_area_start_byte(area, iova) / PAGE_SIZE;
+}
+
 #define __make_iopt_iter(name)                                                 \
 	static inline struct iopt_##name *iopt_##name##_iter_first(            \
 		struct io_pagetable *iopt, unsigned long start,                \
@@ -110,6 +138,33 @@ static inline size_t iopt_area_length(struct iopt_area *area)
 	}
 
 __make_iopt_iter(area)
+__make_iopt_iter(allowed)
+__make_iopt_iter(reserved)
+
+struct iopt_area_contig_iter {
+	unsigned long cur_iova;
+	unsigned long last_iova;
+	struct iopt_area *area;
+};
+struct iopt_area *iopt_area_contig_init(struct iopt_area_contig_iter *iter,
+					struct io_pagetable *iopt,
+					unsigned long iova,
+					unsigned long last_iova);
+struct iopt_area *iopt_area_contig_next(struct iopt_area_contig_iter *iter);
+
+static inline bool iopt_area_contig_done(struct iopt_area_contig_iter *iter)
+{
+	return iter->area && iter->last_iova <= iopt_area_last_iova(iter->area);
+}
+
+/*
+ * Iterate over a contiguous list of areas that span the iova,last_iova range.
+ * The caller must check iopt_area_contig_done() after the loop to see if
+ * contiguous areas existed.
+ */
+#define iopt_for_each_contig_area(iter, area, iopt, iova, last_iova)          \
+	for (area = iopt_area_contig_init(iter, iopt, iova, last_iova); area; \
+	     area = iopt_area_contig_next(iter))
 
 enum {
 	IOPT_PAGES_ACCOUNT_NONE = 0,