[RFC PATCH 13/24] vhost-vdpa: introduce ASID based IOTLB

[Jason Wang <jasowang@redhat.com>]

This patch introduces the support of ASID based IOTLB by tagging IOTLB
with a unique ASID. This is a must for supporting ASID based vhost
IOTLB API by the following patches.

IOTLB were stored in a hlist and new IOTLB will be allocated when a
new ASID is seen via IOTLB API and destoryed when there's no mapping
associated with an ASID.

Signed-off-by: Jason Wang <jasowang@redhat.com>
---
 drivers/vhost/vdpa.c | 94 +++++++++++++++++++++++++++++++++-----------
 1 file changed, 72 insertions(+), 22 deletions(-)

diff --git a/drivers/vhost/vdpa.c b/drivers/vhost/vdpa.c
index 6552987544d7..1ba7e95619b5 100644
--- a/drivers/vhost/vdpa.c
+++ b/drivers/vhost/vdpa.c
@@ -34,13 +34,21 @@ enum {
 
 #define VHOST_VDPA_DEV_MAX (1U << MINORBITS)
 
+#define VHOST_VDPA_IOTLB_BUCKETS 16
+
+struct vhost_vdpa_as {
+	struct hlist_node hash_link;
+	struct vhost_iotlb iotlb;
+	u32 id;
+};
+
 struct vhost_vdpa {
 	struct vhost_dev vdev;
 	struct iommu_domain *domain;
 	struct vhost_virtqueue *vqs;
 	struct completion completion;
 	struct vdpa_device *vdpa;
-	struct vhost_iotlb *iotlb;
+	struct hlist_head as[VHOST_VDPA_IOTLB_BUCKETS];
 	struct device dev;
 	struct cdev cdev;
 	atomic_t opened;
@@ -49,12 +57,64 @@ struct vhost_vdpa {
 	int minor;
 	struct eventfd_ctx *config_ctx;
 	int in_batch;
+	int used_as;
 };
 
 static DEFINE_IDA(vhost_vdpa_ida);
 
 static dev_t vhost_vdpa_major;
 
+static struct vhost_vdpa_as *asid_to_as(struct vhost_vdpa *v, u32 asid)
+{
+	struct hlist_head *head = &v->as[asid % VHOST_VDPA_IOTLB_BUCKETS];
+	struct vhost_vdpa_as *as;
+
+	hlist_for_each_entry(as, head, hash_link)
+		if (as->id == asid)
+			return as;
+
+	return NULL;
+}
+
+static struct vhost_vdpa_as *vhost_vdpa_alloc_as(struct vhost_vdpa *v, u32 asid)
+{
+	struct hlist_head *head = &v->as[asid % VHOST_VDPA_IOTLB_BUCKETS];
+	struct vhost_vdpa_as *as;
+
+	if (asid_to_as(v, asid))
+		return NULL;
+
+	as = kmalloc(sizeof(*as), GFP_KERNEL);
+	if (!as)
+		return NULL;
+
+	vhost_iotlb_init(&as->iotlb, 0, 0);
+	as->id = asid;
+	hlist_add_head(&as->hash_link, head);
+	++v->used_as;
+
+	return as;
+}
+
+static int vhost_vdpa_remove_as(struct vhost_vdpa *v, u32 asid)
+{
+	struct vhost_vdpa_as *as = asid_to_as(v, asid);
+
+	/* Remove default address space is not allowed */
+	if (asid == 0)
+		return -EINVAL;
+
+	if (!as)
+		return -EINVAL;
+
+	hlist_del(&as->hash_link);
+	vhost_iotlb_reset(&as->iotlb);
+	kfree(as);
+	--v->used_as;
+
+	return 0;
+}
+
 static void handle_vq_kick(struct vhost_work *work)
 {
 	struct vhost_virtqueue *vq = container_of(work, struct vhost_virtqueue,
@@ -513,15 +573,6 @@ static void vhost_vdpa_iotlb_unmap(struct vhost_vdpa *v,
 	}
 }
 
-static void vhost_vdpa_iotlb_free(struct vhost_vdpa *v)
-{
-	struct vhost_iotlb *iotlb = v->iotlb;
-
-	vhost_vdpa_iotlb_unmap(v, iotlb, 0ULL, 0ULL - 1);
-	kfree(v->iotlb);
-	v->iotlb = NULL;
-}
-
 static int perm_to_iommu_flags(u32 perm)
 {
 	int flags = 0;
@@ -681,7 +732,8 @@ static int vhost_vdpa_process_iotlb_msg(struct vhost_dev *dev, u32 asid,
 	struct vhost_vdpa *v = container_of(dev, struct vhost_vdpa, vdev);
 	struct vdpa_device *vdpa = v->vdpa;
 	const struct vdpa_config_ops *ops = vdpa->config;
-	struct vhost_iotlb *iotlb = v->iotlb;
+	struct vhost_vdpa_as *as = asid_to_as(v, 0);
+	struct vhost_iotlb *iotlb = &as->iotlb;
 	int r = 0;
 
 	if (asid != 0)
@@ -775,6 +827,7 @@ static void vhost_vdpa_cleanup(struct vhost_vdpa *v)
 {
 	vhost_dev_cleanup(&v->vdev);
 	kfree(v->vdev.vqs);
+	vhost_vdpa_remove_as(v, 0);
 }
 
 static int vhost_vdpa_open(struct inode *inode, struct file *filep)
@@ -807,23 +860,18 @@ static int vhost_vdpa_open(struct inode *inode, struct file *filep)
 	vhost_dev_init(dev, vqs, nvqs, 0, 0, 0, false,
 		       vhost_vdpa_process_iotlb_msg);
 
-	dev->iotlb = vhost_iotlb_alloc(0, 0);
-	if (!dev->iotlb) {
-		r = -ENOMEM;
-		goto err_init_iotlb;
-	}
+	if (!vhost_vdpa_alloc_as(v, 0))
+		goto err_alloc_as;
 
 	r = vhost_vdpa_alloc_domain(v);
 	if (r)
-		goto err_alloc_domain;
+		goto err_alloc_as;
 
 	filep->private_data = v;
 
 	return 0;
 
-err_alloc_domain:
-	vhost_vdpa_iotlb_free(v);
-err_init_iotlb:
+err_alloc_as:
 	vhost_vdpa_cleanup(v);
 err:
 	atomic_dec(&v->opened);
@@ -851,7 +899,6 @@ static int vhost_vdpa_release(struct inode *inode, struct file *filep)
 	filep->private_data = NULL;
 	vhost_vdpa_reset(v);
 	vhost_dev_stop(&v->vdev);
-	vhost_vdpa_iotlb_free(v);
 	vhost_vdpa_free_domain(v);
 	vhost_vdpa_config_put(v);
 	vhost_vdpa_clean_irq(v);
@@ -950,7 +997,7 @@ static int vhost_vdpa_probe(struct vdpa_device *vdpa)
 	const struct vdpa_config_ops *ops = vdpa->config;
 	struct vhost_vdpa *v;
 	int minor;
-	int r;
+	int i, r;
 
 	/* Only support 1 address space */
 	if (vdpa->ngroups != 1)
@@ -1002,6 +1049,9 @@ static int vhost_vdpa_probe(struct vdpa_device *vdpa)
 	init_completion(&v->completion);
 	vdpa_set_drvdata(vdpa, v);
 
+	for (i = 0; i < VHOST_VDPA_IOTLB_BUCKETS; i++)
+		INIT_HLIST_HEAD(&v->as[i]);
+
 	return 0;
 
 err:
-- 
2.20.1