iommufd: Add IOMMU_HWPT_SET_DIRTY_TRACKING

Every IOMMU driver should be able to implement the needed iommu domain ops
to control dirty tracking.

Connect a hw_pagetable to the IOMMU core dirty tracking ops, specifically
the ability to enable/disable dirty tracking on an IOMMU domain
(hw_pagetable id). To that end add an io_pagetable kernel API to toggle
dirty tracking:

* iopt_set_dirty_tracking(iopt, [domain], state)

The intended caller of this is via the hw_pagetable object that is created.

Internally it will ensure the leftover dirty state is cleared /right
before/ dirty tracking starts. This is also useful for iommu drivers which
may decide that dirty tracking is always-enabled at boot without wanting to
toggle dynamically via corresponding iommu domain op.

Link: https://lore.kernel.org/r/20231024135109.73787-7-joao.m.martins@oracle.com
Signed-off-by: Joao Martins <joao.m.martins@oracle.com>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>

drivers/iommu/iommufd/hw_pagetable.c

@@ -196,3 +196,27 @@ out_put_idev:
 	iommufd_put_object(&idev->obj);
 	return rc;
 }
+
+int iommufd_hwpt_set_dirty_tracking(struct iommufd_ucmd *ucmd)
+{
+	struct iommu_hwpt_set_dirty_tracking *cmd = ucmd->cmd;
+	struct iommufd_hw_pagetable *hwpt;
+	struct iommufd_ioas *ioas;
+	int rc = -EOPNOTSUPP;
+	bool enable;
+
+	if (cmd->flags & ~IOMMU_HWPT_DIRTY_TRACKING_ENABLE)
+		return rc;
+
+	hwpt = iommufd_get_hwpt(ucmd, cmd->hwpt_id);
+	if (IS_ERR(hwpt))
+		return PTR_ERR(hwpt);
+
+	ioas = hwpt->ioas;
+	enable = cmd->flags & IOMMU_HWPT_DIRTY_TRACKING_ENABLE;
+
+	rc = iopt_set_dirty_tracking(&ioas->iopt, hwpt->domain, enable);
+
+	iommufd_put_object(&hwpt->obj);
+	return rc;
+}

drivers/iommu/iommufd/io_pagetable.c

@@ -412,6 +412,60 @@ int iopt_map_user_pages(struct iommufd_ctx *ictx, struct io_pagetable *iopt,
 	return 0;
 }
 
+static int iopt_clear_dirty_data(struct io_pagetable *iopt,
+				 struct iommu_domain *domain)
+{
+	const struct iommu_dirty_ops *ops = domain->dirty_ops;
+	struct iommu_iotlb_gather gather;
+	struct iommu_dirty_bitmap dirty;
+	struct iopt_area *area;
+	int ret = 0;
+
+	lockdep_assert_held_read(&iopt->iova_rwsem);
+
+	iommu_dirty_bitmap_init(&dirty, NULL, &gather);
+
+	for (area = iopt_area_iter_first(iopt, 0, ULONG_MAX); area;
+	     area = iopt_area_iter_next(area, 0, ULONG_MAX)) {
+		if (!area->pages)
+			continue;
+
+		ret = ops->read_and_clear_dirty(domain, iopt_area_iova(area),
+						iopt_area_length(area), 0,
+						&dirty);
+		if (ret)
+			break;
+	}
+
+	iommu_iotlb_sync(domain, &gather);
+	return ret;
+}
+
+int iopt_set_dirty_tracking(struct io_pagetable *iopt,
+			    struct iommu_domain *domain, bool enable)
+{
+	const struct iommu_dirty_ops *ops = domain->dirty_ops;
+	int ret = 0;
+
+	if (!ops)
+		return -EOPNOTSUPP;
+
+	down_read(&iopt->iova_rwsem);
+
+	/* Clear dirty bits from PTEs to ensure a clean snapshot */
+	if (enable) {
+		ret = iopt_clear_dirty_data(iopt, domain);
+		if (ret)
+			goto out_unlock;
+	}
+
+	ret = ops->set_dirty_tracking(domain, enable);
+
+out_unlock:
+	up_read(&iopt->iova_rwsem);
+	return ret;
+}
+
 int iopt_get_pages(struct io_pagetable *iopt, unsigned long iova,
 		   unsigned long length, struct list_head *pages_list)
 {

drivers/iommu/iommufd/iommufd_private.h

@@ -8,6 +8,7 @@
 #include <linux/xarray.h>
 #include <linux/refcount.h>
 #include <linux/uaccess.h>
+#include <uapi/linux/iommufd.h>
 
 struct iommu_domain;
 struct iommu_group;
@@ -70,6 +71,9 @@ int iopt_unmap_iova(struct io_pagetable *iopt, unsigned long iova,
 		    unsigned long length, unsigned long *unmapped);
 int iopt_unmap_all(struct io_pagetable *iopt, unsigned long *unmapped);
 
+int iopt_set_dirty_tracking(struct io_pagetable *iopt,
+			    struct iommu_domain *domain, bool enable);
+
 void iommufd_access_notify_unmap(struct io_pagetable *iopt, unsigned long iova,
 				 unsigned long length);
 int iopt_table_add_domain(struct io_pagetable *iopt,
@@ -240,6 +244,14 @@ struct iommufd_hw_pagetable {
 	struct list_head hwpt_item;
 };
 
+static inline struct iommufd_hw_pagetable *
+iommufd_get_hwpt(struct iommufd_ucmd *ucmd, u32 id)
+{
+	return container_of(iommufd_get_object(ucmd->ictx, id,
+					       IOMMUFD_OBJ_HW_PAGETABLE),
+			    struct iommufd_hw_pagetable, obj);
+}
+int iommufd_hwpt_set_dirty_tracking(struct iommufd_ucmd *ucmd);
 struct iommufd_hw_pagetable *
 iommufd_hw_pagetable_alloc(struct iommufd_ctx *ictx, struct iommufd_ioas *ioas,
 			   struct iommufd_device *idev, u32 flags,

drivers/iommu/iommufd/main.c

@@ -307,6 +307,7 @@ union ucmd_buffer {
 	struct iommu_destroy destroy;
 	struct iommu_hw_info info;
 	struct iommu_hwpt_alloc hwpt;
+	struct iommu_hwpt_set_dirty_tracking set_dirty_tracking;
 	struct iommu_ioas_alloc alloc;
 	struct iommu_ioas_allow_iovas allow_iovas;
 	struct iommu_ioas_copy ioas_copy;
@@ -342,6 +343,8 @@ static const struct iommufd_ioctl_op iommufd_ioctl_ops[] = {
 		 __reserved),
 	IOCTL_OP(IOMMU_HWPT_ALLOC, iommufd_hwpt_alloc, struct iommu_hwpt_alloc,
 		 __reserved),
+	IOCTL_OP(IOMMU_HWPT_SET_DIRTY_TRACKING, iommufd_hwpt_set_dirty_tracking,
+		 struct iommu_hwpt_set_dirty_tracking, __reserved),
 	IOCTL_OP(IOMMU_IOAS_ALLOC, iommufd_ioas_alloc_ioctl,
 		 struct iommu_ioas_alloc, out_ioas_id),
 	IOCTL_OP(IOMMU_IOAS_ALLOW_IOVAS, iommufd_ioas_allow_iovas,

include/uapi/linux/iommufd.h

@@ -47,6 +47,7 @@ enum {
 	IOMMUFD_CMD_VFIO_IOAS,
 	IOMMUFD_CMD_HWPT_ALLOC,
 	IOMMUFD_CMD_GET_HW_INFO,
+	IOMMUFD_CMD_HWPT_SET_DIRTY_TRACKING,
 };
 
 /**
@@ -453,4 +454,31 @@ struct iommu_hw_info {
 	__u32 __reserved;
 };
 #define IOMMU_GET_HW_INFO _IO(IOMMUFD_TYPE, IOMMUFD_CMD_GET_HW_INFO)
+
+/*
+ * enum iommufd_hwpt_set_dirty_tracking_flags - Flags for steering dirty
+ *                                              tracking
+ * @IOMMU_HWPT_DIRTY_TRACKING_ENABLE: Enable dirty tracking
+ */
+enum iommufd_hwpt_set_dirty_tracking_flags {
+	IOMMU_HWPT_DIRTY_TRACKING_ENABLE = 1,
+};
+
+/**
+ * struct iommu_hwpt_set_dirty_tracking - ioctl(IOMMU_HWPT_SET_DIRTY_TRACKING)
+ * @size: sizeof(struct iommu_hwpt_set_dirty_tracking)
+ * @flags: Combination of enum iommufd_hwpt_set_dirty_tracking_flags
+ * @hwpt_id: HW pagetable ID that represents the IOMMU domain
+ * @__reserved: Must be 0
+ *
+ * Toggle dirty tracking on an HW pagetable.
+ */
+struct iommu_hwpt_set_dirty_tracking {
+	__u32 size;
+	__u32 flags;
+	__u32 hwpt_id;
+	__u32 __reserved;
+};
+#define IOMMU_HWPT_SET_DIRTY_TRACKING _IO(IOMMUFD_TYPE, \
+					  IOMMUFD_CMD_HWPT_SET_DIRTY_TRACKING)
 #endif