[PATCH v5 14/29] iommufd/viommu: Add IOMMUFD_CMD_HW_QUEUE_ALLOC ioctl

Nicolin Chen
2025-05-18T03:51:12Z

Introduce a new IOMMUFD_CMD_HW_QUEUE_ALLOC ioctl for user space to allocate
a HW QUEUE object for a vIOMMU specific HW-accelerated queue, e.g.:
- NVIDIA's Virtual Command Queue
- AMD vIOMMU's Command Buffer, Event Log Buffer, and PPR Log Buffer

This is a vIOMMU based ioctl. Simply increase the refcount of the vIOMMU.

Reviewed-by: Pranjal Shrivastava <praan@google.com>
Signed-off-by: Nicolin Chen <nicolinc@nvidia.com>
---
drivers/iommu/iommufd/iommufd_private.h | 2 +
include/uapi/linux/iommufd.h | 45 ++++++++++
drivers/iommu/iommufd/main.c | 6 ++
drivers/iommu/iommufd/viommu.c | 105 ++++++++++++++++++++++++
4 files changed, 158 insertions(+)

diff --git a/drivers/iommu/iommufd/iommufd_private.h b/drivers/iommu/iommufd/iommufd_private.h
index 35088478cb07..a94d04ab0d2c 100644
--- a/drivers/iommu/iommufd/iommufd_private.h
+++ b/drivers/iommu/iommufd/iommufd_private.h
@@ -603,6 +603,8 @@ int iommufd_viommu_alloc_ioctl(struct iommufd_ucmd *ucmd);
void iommufd_viommu_destroy(struct iommufd_object *obj);
int iommufd_vdevice_alloc_ioctl(struct iommufd_ucmd *ucmd);
void iommufd_vdevice_destroy(struct iommufd_object *obj);
+int iommufd_hw_queue_alloc_ioctl(struct iommufd_ucmd *ucmd);
+void iommufd_hw_queue_destroy(struct iommufd_object *obj);

#ifdef CONFIG_IOMMUFD_TEST
int iommufd_test(struct iommufd_ucmd *ucmd);
diff --git a/include/uapi/linux/iommufd.h b/include/uapi/linux/iommufd.h
index 272da7324a2b..aeed0127553e 100644
--- a/include/uapi/linux/iommufd.h
+++ b/include/uapi/linux/iommufd.h
@@ -56,6 +56,7 @@ enum {
IOMMUFD_CMD_VDEVICE_ALLOC = 0x91,
IOMMUFD_CMD_IOAS_CHANGE_PROCESS = 0x92,
IOMMUFD_CMD_VEVENTQ_ALLOC = 0x93,
+ IOMMUFD_CMD_HW_QUEUE_ALLOC = 0x94,
};

/**
@@ -1147,4 +1148,48 @@ struct iommu_veventq_alloc {
__u32 __reserved;
};
#define IOMMU_VEVENTQ_ALLOC _IO(IOMMUFD_TYPE, IOMMUFD_CMD_VEVENTQ_ALLOC)
+
+/**
+ * enum iommu_hw_queue_type - HW Queue Type
+ * @IOMMU_HW_QUEUE_TYPE_DEFAULT: Reserved for future use
+ */
+enum iommu_hw_queue_type {
+ IOMMU_HW_QUEUE_TYPE_DEFAULT = 0,
+};
+
+/**
+ * struct iommu_hw_queue_alloc - ioctl(IOMMU_HW_QUEUE_ALLOC)
+ * @size: sizeof(struct iommu_hw_queue_alloc)
+ * @flags: Must be 0
+ * @viommu_id: Virtual IOMMU ID to associate the HW queue with
+ * @type: One of enum iommu_hw_queue_type
+ * @index: The logical index to the HW queue per virtual IOMMU for a multi-queue
+ * model
+ * @out_hw_queue_id: The ID of the new HW queue
+ * @nesting_parent_iova: Base address of the queue memory in the guest physical
+ * address space
+ * @length: Length of the queue memory
+ *
+ * Allocate a HW queue object for a vIOMMU-specific HW-accelerated queue, which
+ * allows HW to access a guest queue memory described using @nesting_parent_iova
+ * and @length.
+ *
+ * Upon success, the underlying physical pages of the guest queue memory will be
+ * pinned to prevent VMM from unmapping them in the IOAS until the HW queue gets
+ * destroyed.
+ *
+ * A vIOMMU can allocate multiple queues, but it must use a different @index to
+ * separate each allocation, e.g. HW queue0, HW queue1, ...
+ */
+struct iommu_hw_queue_alloc {
+ __u32 size;
+ __u32 flags;
+ __u32 viommu_id;
+ __u32 type;
+ __u32 index;
+ __u32 out_hw_queue_id;
+ __aligned_u64 nesting_parent_iova;
+ __aligned_u64 length;
+};
+#define IOMMU_HW_QUEUE_ALLOC _IO(IOMMUFD_TYPE, IOMMUFD_CMD_HW_QUEUE_ALLOC)
#endif
diff --git a/drivers/iommu/iommufd/main.c b/drivers/iommu/iommufd/main.c
index c6d0b446e632..0750e740fa1d 100644
--- a/drivers/iommu/iommufd/main.c
+++ b/drivers/iommu/iommufd/main.c
@@ -304,6 +304,7 @@ union ucmd_buffer {
struct iommu_destroy destroy;
struct iommu_fault_alloc fault;
struct iommu_hw_info info;
+ struct iommu_hw_queue_alloc hw_queue;
struct iommu_hwpt_alloc hwpt;
struct iommu_hwpt_get_dirty_bitmap get_dirty_bitmap;
struct iommu_hwpt_invalidate cache;
@@ -346,6 +347,8 @@ static const struct iommufd_ioctl_op iommufd_ioctl_ops[] = {
struct iommu_fault_alloc, out_fault_fd),
IOCTL_OP(IOMMU_GET_HW_INFO, iommufd_get_hw_info, struct iommu_hw_info,
__reserved),
+ IOCTL_OP(IOMMU_HW_QUEUE_ALLOC, iommufd_hw_queue_alloc_ioctl,
+ struct iommu_hw_queue_alloc, length),
IOCTL_OP(IOMMU_HWPT_ALLOC, iommufd_hwpt_alloc, struct iommu_hwpt_alloc,
__reserved),
IOCTL_OP(IOMMU_HWPT_GET_DIRTY_BITMAP, iommufd_hwpt_get_dirty_bitmap,
@@ -509,6 +512,9 @@ static const struct iommufd_object_ops iommufd_object_ops[] = {
[IOMMUFD_OBJ_FAULT] = {
.destroy = iommufd_fault_destroy,
},
+ [IOMMUFD_OBJ_HW_QUEUE] = {
+ .destroy = iommufd_hw_queue_destroy,
+ },
[IOMMUFD_OBJ_HWPT_PAGING] = {
.destroy = iommufd_hwpt_paging_destroy,
.abort = iommufd_hwpt_paging_abort,
diff --git a/drivers/iommu/iommufd/viommu.c b/drivers/iommu/iommufd/viommu.c
index 7248fb7c7baf..9b4e99babdb4 100644
--- a/drivers/iommu/iommufd/viommu.c
+++ b/drivers/iommu/iommufd/viommu.c
@@ -164,3 +164,108 @@ int iommufd_vdevice_alloc_ioctl(struct iommufd_ucmd *ucmd)
iommufd_put_object(ucmd->ictx, &viommu->obj);
return rc;
}
+
+void iommufd_hw_queue_destroy(struct iommufd_object *obj)
+{
+ struct iommufd_hw_queue *hw_queue =
+ container_of(obj, struct iommufd_hw_queue, obj);
+ struct iommufd_viommu *viommu = hw_queue->viommu;
+
+ if (viommu->ops->hw_queue_destroy)
+ viommu->ops->hw_queue_destroy(hw_queue);
+ iopt_unpin_pages(&viommu->hwpt->ioas->iopt, hw_queue->base_addr,
+ hw_queue->length, true);
+ refcount_dec(&viommu->obj.users);
+}
+
+int iommufd_hw_queue_alloc_ioctl(struct iommufd_ucmd *ucmd)
+{
+ struct iommu_hw_queue_alloc *cmd = ucmd->cmd;
+ struct iommufd_hw_queue *hw_queue;
+ struct iommufd_viommu *viommu;
+ struct page **pages;
+ int max_npages, i;
+ u64 last, offset;
+ int rc;
+
+ if (cmd->flags || cmd->type == IOMMU_HW_QUEUE_TYPE_DEFAULT)
+ return -EOPNOTSUPP;
+ if (!cmd->nesting_parent_iova || !cmd->length)
+ return -EINVAL;
+ if (check_add_overflow(cmd->nesting_parent_iova, cmd->length - 1,
+ &last))
+ return -EOVERFLOW;
+
+ viommu = iommufd_get_viommu(ucmd, cmd->viommu_id);
+ if (IS_ERR(viommu))
+ return PTR_ERR(viommu);
+
+ if (!viommu->ops || !viommu->ops->hw_queue_alloc) {
+ rc = -EOPNOTSUPP;
+ goto out_put_viommu;
+ }
+
+ offset =
+ cmd->nesting_parent_iova - PAGE_ALIGN(cmd->nesting_parent_iova);
+ max_npages = DIV_ROUND_UP(offset + cmd->length, PAGE_SIZE);
+ pages = kcalloc(max_npages, sizeof(*pages), GFP_KERNEL);
+ if (!pages) {
+ rc = -ENOMEM;
+ goto out_put_viommu;
+ }
+
+ /*
+ * The underlying physical pages must be pinned to prevent them from
+ * being unmapped (via IOMMUFD_CMD_IOAS_UNMAP) during the life cycle
+ * of the HW QUEUE object. And the pages should be contiguous too.
+ */
+ if (viommu->ops->flags & IOMMUFD_VIOMMU_FLAG_HW_QUEUE_READS_PA) {
+ rc = iopt_pin_pages(&viommu->hwpt->ioas->iopt,
+ cmd->nesting_parent_iova, cmd->length,
+ pages, 0, true);
+ if (rc)
+ goto out_free;
+
+ /* Validate if the underlying physical pages are contiguous */
+ for (i = 1; i < max_npages && pages[i]; i++) {
+ if (page_to_pfn(pages[i]) ==
+ page_to_pfn(pages[i - 1]) + 1)
+ continue;
+ rc = -EFAULT;
+ goto out_unpin;
+ }
+ }
+
+ hw_queue = viommu->ops->hw_queue_alloc(ucmd, viommu, cmd->type,
+ cmd->index,
+ cmd->nesting_parent_iova,
+ cmd->length);
+ if (IS_ERR(hw_queue)) {
+ rc = PTR_ERR(hw_queue);
+ goto out_unpin;
+ }
+
+ /* The iommufd_hw_queue_alloc helper saves ictx in hw_queue->ictx */
+ if (WARN_ON_ONCE(hw_queue->ictx != ucmd->ictx)) {
+ rc = -EINVAL;
+ goto out_unpin;
+ }
+
+ hw_queue->viommu = viommu;
+ refcount_inc(&viommu->obj.users);
+ hw_queue->length = cmd->length;
+ hw_queue->base_addr = cmd->nesting_parent_iova;
+ cmd->out_hw_queue_id = hw_queue->obj.id;
+ rc = iommufd_ucmd_respond(ucmd, sizeof(*cmd));
+ goto out_put_viommu;
+
+out_unpin:
+ if (viommu->ops->flags & IOMMUFD_VIOMMU_FLAG_HW_QUEUE_READS_PA)
+ iopt_unpin_pages(&viommu->hwpt->ioas->iopt,
+ cmd->nesting_parent_iova, cmd->length, true);
+out_free:
+ kfree(pages);
+out_put_viommu:
+ iommufd_put_object(ucmd->ictx, &viommu->obj);
+ return rc;
+}
--
2.43.0