[PATCH v6 3/3] iommufd: Add IOMMU_IOAS_RESERVE_IOVAS ioctl

[Guanghui Feng <guanghuifeng@linux.alibaba.com>]

Add an ioctl allowing userspace to reserve IOVA ranges in an IOAS,
creating a restriction on the address space: reserved ranges are
excluded from IOMMU_IOAS_IOVA_RANGES and rejected by mapping
operations.

This completes the opt-in flow for the kernel's reservation
recommendations: userspace queries IOMMU_GET_RECOMMENDED_RESERVATIONS
for a device, decides which ranges to honour, and feeds them back
through this ioctl so the kernel enforces them on its behalf.  Both
steps are optional; nothing changes for userspace that does not use
them.

The semantics mirror the existing internal users of
iopt_reserve_iova(): ranges conflicting with existing mappings or
allowed IOVAs fail with -EADDRINUSE, and overlapping reservations are
permitted so that recommendations queried for several devices behind
the same host bridge can each be reserved independently.  User
reservations carry a NULL owner and live until the IOAS is destroyed;
accordingly the NULL-owner cleanup in iopt_destroy_table() is no
longer conditional on CONFIG_IOMMUFD_TEST, since production userspace
can now create such reservations.

On failure the leading ranges already inserted stay reserved; because
overlaps are permitted, retrying the whole call is idempotent.

Signed-off-by: Guanghui Feng <guanghuifeng@linux.alibaba.com>
---
 drivers/iommu/iommufd/io_pagetable.c    |  7 +++-
 drivers/iommu/iommufd/ioas.c            | 51 +++++++++++++++++++++++++
 drivers/iommu/iommufd/iommufd_private.h |  1 +
 drivers/iommu/iommufd/main.c            |  3 ++
 include/uapi/linux/iommufd.h            | 35 +++++++++++++++++
 5 files changed, 95 insertions(+), 2 deletions(-)

diff --git a/drivers/iommu/iommufd/io_pagetable.c b/drivers/iommu/iommufd/io_pagetable.c
index 5ac736cf5bb5..9a10daf6491e 100644
--- a/drivers/iommu/iommufd/io_pagetable.c
+++ b/drivers/iommu/iommufd/io_pagetable.c
@@ -1036,8 +1036,11 @@ void iopt_destroy_table(struct io_pagetable *iopt)
 {
 	struct interval_tree_node *node;
 
-	if (IS_ENABLED(CONFIG_IOMMUFD_TEST))
-		iopt_remove_reserved_iova(iopt, NULL);
+	/*
+	 * Reservations made by userspace through IOMMU_IOAS_RESERVE_IOVAS
+	 * carry a NULL owner and live until the IOAS is destroyed.
+	 */
+	iopt_remove_reserved_iova(iopt, NULL);
 
 	while ((node = interval_tree_iter_first(&iopt->allowed_itree, 0,
 						ULONG_MAX))) {
diff --git a/drivers/iommu/iommufd/ioas.c b/drivers/iommu/iommufd/ioas.c
index 8fb5271a9506..1a2361850bd2 100644
--- a/drivers/iommu/iommufd/ioas.c
+++ b/drivers/iommu/iommufd/ioas.c
@@ -183,6 +183,57 @@ int iommufd_ioas_allow_iovas(struct iommufd_ucmd *ucmd)
 	return rc;
 }
 
+int iommufd_ioas_reserve_iovas(struct iommufd_ucmd *ucmd)
+{
+	struct iommu_ioas_reserve_iovas *cmd = ucmd->cmd;
+	struct iommu_iova_range __user *ranges;
+	struct iommufd_ioas *ioas;
+	u32 i;
+	int rc;
+
+	if (cmd->flags)
+		return -EOPNOTSUPP;
+
+	ioas = iommufd_get_ioas(ucmd->ictx, cmd->ioas_id);
+	if (IS_ERR(ioas))
+		return PTR_ERR(ioas);
+
+	ranges = u64_to_user_ptr(cmd->ranges);
+
+	down_write(&ioas->iopt.iova_rwsem);
+	for (i = 0; i < cmd->num_ranges; i++) {
+		struct iommu_iova_range range;
+
+		rc = copy_from_user(&range, &ranges[i], sizeof(range));
+		if (rc) {
+			rc = -EFAULT;
+			goto out_unlock;
+		}
+		if (range.last < range.start) {
+			rc = -EINVAL;
+			goto out_unlock;
+		}
+		if (range.start >= ULONG_MAX || range.last >= ULONG_MAX) {
+			rc = -EOVERFLOW;
+			goto out_unlock;
+		}
+
+		rc = iopt_reserve_iova(&ioas->iopt, range.start, range.last,
+				       NULL);
+		if (rc)
+			goto out_unlock;
+	}
+	up_write(&ioas->iopt.iova_rwsem);
+
+	iommufd_put_object(ucmd->ictx, &ioas->obj);
+	return 0;
+
+out_unlock:
+	up_write(&ioas->iopt.iova_rwsem);
+	iommufd_put_object(ucmd->ictx, &ioas->obj);
+	return rc;
+}
+
 static int conv_iommu_prot(u32 map_flags)
 {
 	/*
diff --git a/drivers/iommu/iommufd/iommufd_private.h b/drivers/iommu/iommufd/iommufd_private.h
index 8016c3efca78..361223372cf3 100644
--- a/drivers/iommu/iommufd/iommufd_private.h
+++ b/drivers/iommu/iommufd/iommufd_private.h
@@ -356,6 +356,7 @@ int iommufd_ioas_map(struct iommufd_ucmd *ucmd);
 int iommufd_ioas_map_file(struct iommufd_ucmd *ucmd);
 int iommufd_ioas_change_process(struct iommufd_ucmd *ucmd);
 int iommufd_ioas_copy(struct iommufd_ucmd *ucmd);
+int iommufd_ioas_reserve_iovas(struct iommufd_ucmd *ucmd);
 int iommufd_ioas_unmap(struct iommufd_ucmd *ucmd);
 #ifdef CONFIG_IOMMUFD_NOIOMMU
 int iommufd_ioas_noiommu_get_pa(struct iommufd_ucmd *ucmd);
diff --git a/drivers/iommu/iommufd/main.c b/drivers/iommu/iommufd/main.c
index 85f8ea154218..ea03a2078a37 100644
--- a/drivers/iommu/iommufd/main.c
+++ b/drivers/iommu/iommufd/main.c
@@ -447,6 +447,7 @@ union ucmd_buffer {
 	struct iommu_ioas_noiommu_get_pa noiommu_get_pa;
 	struct iommu_ioas_iova_ranges iova_ranges;
 	struct iommu_ioas_map map;
+	struct iommu_ioas_reserve_iovas ioas_reserve_iovas;
 	struct iommu_ioas_unmap unmap;
 	struct iommu_option option;
 	struct iommu_recommended_reservations recommended_reservations;
@@ -509,6 +510,8 @@ static const struct iommufd_ioctl_op iommufd_ioctl_ops[] = {
 		 struct iommu_ioas_map_file, iova),
 	IOCTL_OP(IOMMU_IOAS_NOIOMMU_GET_PA, iommufd_ioas_noiommu_get_pa, struct iommu_ioas_noiommu_get_pa,
 		 out_phys),
+	IOCTL_OP(IOMMU_IOAS_RESERVE_IOVAS, iommufd_ioas_reserve_iovas,
+		 struct iommu_ioas_reserve_iovas, ranges),
 	IOCTL_OP(IOMMU_IOAS_UNMAP, iommufd_ioas_unmap, struct iommu_ioas_unmap,
 		 length),
 	IOCTL_OP(IOMMU_OPTION, iommufd_option, struct iommu_option, val64),
diff --git a/include/uapi/linux/iommufd.h b/include/uapi/linux/iommufd.h
index 45ba7bd7abd5..f6591c42ad5c 100644
--- a/include/uapi/linux/iommufd.h
+++ b/include/uapi/linux/iommufd.h
@@ -59,6 +59,7 @@ enum {
 	IOMMUFD_CMD_HW_QUEUE_ALLOC = 0x94,
 	IOMMUFD_CMD_IOAS_NOIOMMU_GET_PA = 0x95,
 	IOMMUFD_CMD_GET_RECOMMENDED_RESERVATIONS = 0x96,
+	IOMMUFD_CMD_IOAS_RESERVE_IOVAS = 0x97,
 };
 
 /**
@@ -1436,4 +1437,38 @@ struct iommu_recommended_reservations {
 };
 #define IOMMU_GET_RECOMMENDED_RESERVATIONS \
 	_IO(IOMMUFD_TYPE, IOMMUFD_CMD_GET_RECOMMENDED_RESERVATIONS)
+
+/**
+ * struct iommu_ioas_reserve_iovas - ioctl(IOMMU_IOAS_RESERVE_IOVAS)
+ * @size: sizeof(struct iommu_ioas_reserve_iovas)
+ * @flags: Must be 0
+ * @ioas_id: IOAS ID to reserve ranges in
+ * @num_ranges: Number of ranges in the input array
+ * @ranges: Pointer to the input array of struct iommu_iova_range
+ *
+ * Reserve IOVA ranges in an IOAS, excluding them from mapping and from
+ * IOMMU_IOAS_IOVA_RANGES.  Intended for opting into the ranges
+ * reported by IOMMU_GET_RECOMMENDED_RESERVATIONS.
+ *
+ * Reserve before mapping: a range overlapping an existing mapping or
+ * an allowed IOVA range fails with -EADDRINUSE.  Overlapping
+ * reservations are permitted, so ranges recommended for multiple
+ * devices (e.g. behind the same host bridge) can each be reserved.
+ * A range with last < start fails with -EINVAL.  On 32-bit kernels
+ * a range exceeding the native address width fails with -EOVERFLOW.
+ * Ranges are processed in order and earlier ranges stay reserved on
+ * failure; retrying the whole call is safe.  Reservations live until
+ * the IOAS is destroyed.
+ *
+ * Return: 0 on success, negative errno on failure.
+ */
+struct iommu_ioas_reserve_iovas {
+	__u32 size;
+	__u32 flags;
+	__u32 ioas_id;
+	__u32 num_ranges;
+	__aligned_u64 ranges;
+};
+#define IOMMU_IOAS_RESERVE_IOVAS \
+	_IO(IOMMUFD_TYPE, IOMMUFD_CMD_IOAS_RESERVE_IOVAS)
 #endif
-- 
2.43.7