IB/mlx5: Implements disassociate_ucontext API

Implements the IB core disassociate_ucontext API.
The driver detaches the HW resources for a given user context to
prevent a dependency between application termination and device
disconnect. This is done by managing the VMAs that were mapped
to the HW bars such as doorbell and blueflame. When need to detach,
remap them to an arbitrary kernel page returned by the zap API.

Signed-off-by: Maor Gottlieb <maorg@mellanox.com>
Signed-off-by: Leon Romanovsky <leon@kernel.org>
Signed-off-by: Doug Ledford <dledford@redhat.com>

drivers/infiniband/hw/mlx5/main.c

@@ -42,11 +42,13 @@
 #include <asm/pat.h>
 #endif
 #include <linux/sched.h>
+#include <linux/delay.h>
 #include <rdma/ib_user_verbs.h>
 #include <rdma/ib_addr.h>
 #include <rdma/ib_cache.h>
 #include <linux/mlx5/port.h>
 #include <linux/mlx5/vport.h>
+#include <linux/list.h>
 #include <rdma/ib_smi.h>
 #include <rdma/ib_umem.h>
 #include <linux/in.h>
@@ -983,6 +985,7 @@ static struct ib_ucontext *mlx5_ib_alloc_ucontext(struct ib_device *ibdev,
 			goto out_uars;
 	}
 
+	INIT_LIST_HEAD(&context->vma_private_list);
 	INIT_LIST_HEAD(&context->db_page_list);
 	mutex_init(&context->db_page_mutex);
 
@@ -1086,6 +1089,125 @@ static int get_index(unsigned long offset)
 	return get_arg(offset);
 }
 
+static void  mlx5_ib_vma_open(struct vm_area_struct *area)
+{
+	/* vma_open is called when a new VMA is created on top of our VMA.  This
+	 * is done through either mremap flow or split_vma (usually due to
+	 * mlock, madvise, munmap, etc.) We do not support a clone of the VMA,
+	 * as this VMA is strongly hardware related.  Therefore we set the
+	 * vm_ops of the newly created/cloned VMA to NULL, to prevent it from
+	 * calling us again and trying to do incorrect actions.  We assume that
+	 * the original VMA size is exactly a single page, and therefore all
+	 * "splitting" operation will not happen to it.
+	 */
+	area->vm_ops = NULL;
+}
+
+static void  mlx5_ib_vma_close(struct vm_area_struct *area)
+{
+	struct mlx5_ib_vma_private_data *mlx5_ib_vma_priv_data;
+
+	/* It's guaranteed that all VMAs opened on a FD are closed before the
+	 * file itself is closed, therefore no sync is needed with the regular
+	 * closing flow. (e.g. mlx5 ib_dealloc_ucontext)
+	 * However need a sync with accessing the vma as part of
+	 * mlx5_ib_disassociate_ucontext.
+	 * The close operation is usually called under mm->mmap_sem except when
+	 * process is exiting.
+	 * The exiting case is handled explicitly as part of
+	 * mlx5_ib_disassociate_ucontext.
+	 */
+	mlx5_ib_vma_priv_data = (struct mlx5_ib_vma_private_data *)area->vm_private_data;
+
+	/* setting the vma context pointer to null in the mlx5_ib driver's
+	 * private data, to protect a race condition in
+	 * mlx5_ib_disassociate_ucontext().
+	 */
+	mlx5_ib_vma_priv_data->vma = NULL;
+	list_del(&mlx5_ib_vma_priv_data->list);
+	kfree(mlx5_ib_vma_priv_data);
+}
+
+static const struct vm_operations_struct mlx5_ib_vm_ops = {
+	.open = mlx5_ib_vma_open,
+	.close = mlx5_ib_vma_close
+};
+
+static int mlx5_ib_set_vma_data(struct vm_area_struct *vma,
+				struct mlx5_ib_ucontext *ctx)
+{
+	struct mlx5_ib_vma_private_data *vma_prv;
+	struct list_head *vma_head = &ctx->vma_private_list;
+
+	vma_prv = kzalloc(sizeof(*vma_prv), GFP_KERNEL);
+	if (!vma_prv)
+		return -ENOMEM;
+
+	vma_prv->vma = vma;
+	vma->vm_private_data = vma_prv;
+	vma->vm_ops =  &mlx5_ib_vm_ops;
+
+	list_add(&vma_prv->list, vma_head);
+
+	return 0;
+}
+
+static void mlx5_ib_disassociate_ucontext(struct ib_ucontext *ibcontext)
+{
+	int ret;
+	struct vm_area_struct *vma;
+	struct mlx5_ib_vma_private_data *vma_private, *n;
+	struct mlx5_ib_ucontext *context = to_mucontext(ibcontext);
+	struct task_struct *owning_process  = NULL;
+	struct mm_struct   *owning_mm       = NULL;
+
+	owning_process = get_pid_task(ibcontext->tgid, PIDTYPE_PID);
+	if (!owning_process)
+		return;
+
+	owning_mm = get_task_mm(owning_process);
+	if (!owning_mm) {
+		pr_info("no mm, disassociate ucontext is pending task termination\n");
+		while (1) {
+			put_task_struct(owning_process);
+			usleep_range(1000, 2000);
+			owning_process = get_pid_task(ibcontext->tgid,
+						      PIDTYPE_PID);
+			if (!owning_process ||
+			    owning_process->state == TASK_DEAD) {
+				pr_info("disassociate ucontext done, task was terminated\n");
+				/* in case task was dead need to release the
+				 * task struct.
+				 */
+				if (owning_process)
+					put_task_struct(owning_process);
+				return;
+			}
+		}
+	}
+
+	/* need to protect from a race on closing the vma as part of
+	 * mlx5_ib_vma_close.
+	 */
+	down_read(&owning_mm->mmap_sem);
+	list_for_each_entry_safe(vma_private, n, &context->vma_private_list,
+				 list) {
+		vma = vma_private->vma;
+		ret = zap_vma_ptes(vma, vma->vm_start,
+				   PAGE_SIZE);
+		WARN_ONCE(ret, "%s: zap_vma_ptes failed", __func__);
+		/* context going to be destroyed, should
+		 * not access ops any more.
+		 */
+		vma->vm_ops = NULL;
+		list_del(&vma_private->list);
+		kfree(vma_private);
+	}
+	up_read(&owning_mm->mmap_sem);
+	mmput(owning_mm);
+	put_task_struct(owning_process);
+}
+
 static inline char *mmap_cmd2str(enum mlx5_ib_mmap_cmd cmd)
 {
 	switch (cmd) {
@@ -1101,8 +1223,10 @@ static inline char *mmap_cmd2str(enum mlx5_ib_mmap_cmd cmd)
 }
 
 static int uar_mmap(struct mlx5_ib_dev *dev, enum mlx5_ib_mmap_cmd cmd,
-		    struct vm_area_struct *vma, struct mlx5_uuar_info *uuari)
+		    struct vm_area_struct *vma,
+		    struct mlx5_ib_ucontext *context)
 {
+	struct mlx5_uuar_info *uuari = &context->uuari;
 	int err;
 	unsigned long idx;
 	phys_addr_t pfn, pa;
@@ -1152,14 +1276,13 @@ static int uar_mmap(struct mlx5_ib_dev *dev, enum mlx5_ib_mmap_cmd cmd,
 	mlx5_ib_dbg(dev, "mapped %s at 0x%lx, PA %pa\n", mmap_cmd2str(cmd),
 		    vma->vm_start, &pa);
 
-	return 0;
+	return mlx5_ib_set_vma_data(vma, context);
 }
 
 static int mlx5_ib_mmap(struct ib_ucontext *ibcontext, struct vm_area_struct *vma)
 {
 	struct mlx5_ib_ucontext *context = to_mucontext(ibcontext);
 	struct mlx5_ib_dev *dev = to_mdev(ibcontext->device);
-	struct mlx5_uuar_info *uuari = &context->uuari;
 	unsigned long command;
 	phys_addr_t pfn;
 
@@ -1168,7 +1291,7 @@ static int mlx5_ib_mmap(struct ib_ucontext *ibcontext, struct vm_area_struct *vm
 	case MLX5_IB_MMAP_WC_PAGE:
 	case MLX5_IB_MMAP_NC_PAGE:
 	case MLX5_IB_MMAP_REGULAR_PAGE:
-		return uar_mmap(dev, command, vma, uuari);
+		return uar_mmap(dev, command, vma, context);
 
 	case MLX5_IB_MMAP_GET_CONTIGUOUS_PAGES:
 		return -ENOSYS;
@@ -2428,6 +2551,8 @@ static void *mlx5_ib_add(struct mlx5_core_dev *mdev)
 		dev->ib_dev.set_vf_guid		= mlx5_ib_set_vf_guid;
 	}
 
+	dev->ib_dev.disassociate_ucontext = mlx5_ib_disassociate_ucontext;
+
 	mlx5_ib_internal_fill_odp_caps(dev);
 
 	if (MLX5_CAP_GEN(mdev, imaicl)) {

drivers/infiniband/hw/mlx5/mlx5_ib.h

@@ -105,6 +105,11 @@ enum {
 	MLX5_CQE_VERSION_V1,
 };
 
+struct mlx5_ib_vma_private_data {
+	struct list_head list;
+	struct vm_area_struct *vma;
+};
+
 struct mlx5_ib_ucontext {
 	struct ib_ucontext	ibucontext;
 	struct list_head	db_page_list;
@@ -116,6 +121,7 @@ struct mlx5_ib_ucontext {
 	u8			cqe_version;
 	/* Transport Domain number */
 	u32			tdn;
+	struct list_head	vma_private_list;
 };
 
 static inline struct mlx5_ib_ucontext *to_mucontext(struct ib_ucontext *ibucontext)