[Xen-devel] [PATCH v2 12/18] argo: implement the unregister op

[Christopher Clark <christopher.w.clark@xxxxxxxxx>]

Takes a single argument: a handle to the registered ring.

The ring's entry is removed from the hashtable of registered rings;
any entries for pending notifications are removed; and the ring is
unmapped from Xen's address space.

Signed-off-by: Christopher Clark <christopher.clark6@xxxxxxxxxxxxxx>
---
Changes since v1:

v1 #5 (#14) feedback Paul: use currd in do_argo_message_op
v1 #5 (#14) feedback Paul: full use currd in argo_unregister_ring
v1 #13 (#14) feedback Paul: replace do/while with goto; reindent
v1 self: add blank lines in unregister case in do_argo_message_op
v1: #13 feedback Jan: public namespace: prefix with xen
v1: #13 feedback Jan: blank line after op case in do_argo_message_op
v1: #14 feedback Jan: replace domain id override with validation
v1: #18 feedback Jan: meld the ring count limit into the series
v1: feedback #15 Jan: verify zero in unused hypercall args

 xen/common/argo.c         | 76 +++++++++++++++++++++++++++++++++++++++++++++++
 xen/include/public/argo.h | 12 ++++++++
 2 files changed, 88 insertions(+)

diff --git a/xen/common/argo.c b/xen/common/argo.c
index 81f8341..cbb17a3 100644
--- a/xen/common/argo.c
+++ b/xen/common/argo.c
@@ -565,6 +565,65 @@ argo_ring_find_info(const struct domain *d, const struct 
xen_argo_ring_id *id)
     return NULL;
 }
 
+static long
+argo_unregister_ring(struct domain *currd,
+                     XEN_GUEST_HANDLE_PARAM(xen_argo_ring_t) ring_hnd)
+{
+    struct xen_argo_ring ring;
+    struct argo_ring_info *ring_info;
+    int ret = 0;
+
+    read_lock(&argo_lock);
+
+    if ( !currd->argo )
+    {
+        ret = -ENODEV;
+        goto out;
+    }
+
+    ret = copy_from_guest_errno(&ring, ring_hnd, 1);
+    if ( ret )
+        goto out;
+
+    if ( ring.magic != XEN_ARGO_RING_MAGIC )
+    {
+        argo_dprintk(
+            "ring.magic(%"PRIx64") != XEN_ARGO_RING_MAGIC(%llx), EINVAL\n",
+            ring.magic, XEN_ARGO_RING_MAGIC);
+        ret = -EINVAL;
+        goto out;
+    }
+
+    if ( unlikely(ring.id.addr.domain_id != currd->domain_id) )
+    {
+        ret = -EPERM;
+        goto out;
+    }
+
+    write_lock(&currd->argo->lock);
+
+    ring_info = argo_ring_find_info(currd, &ring.id);
+    if ( ring_info )
+    {
+        argo_ring_remove_info(currd, ring_info);
+        currd->argo->ring_count--;
+    }
+
+    write_unlock(&currd->argo->lock);
+
+    if ( !ring_info )
+    {
+        argo_dprintk("ENOENT\n");
+        ret = -ENOENT;
+        goto out;
+    }
+
+ out:
+    read_unlock(&argo_lock);
+
+    return ret;
+}
+
 static int
 argo_verify_ring_magic(struct argo_ring_info *ring_info)
 {
@@ -882,6 +941,23 @@ do_argo_message_op(unsigned int cmd, 
XEN_GUEST_HANDLE_PARAM(void) arg1,
         break;
     }
 
+    case XEN_ARGO_MESSAGE_OP_unregister_ring:
+    {
+        XEN_GUEST_HANDLE_PARAM(xen_argo_ring_t) ring_hnd =
+            guest_handle_cast(arg1, xen_argo_ring_t);
+
+        if ( unlikely(!guest_handle_okay(ring_hnd, 1)) )
+            break;
+        if ( unlikely((!guest_handle_is_null(arg2)) || arg3 || arg4) )
+        {
+            rc = -EINVAL;
+            break;
+        }
+
+        rc = argo_unregister_ring(currd, ring_hnd);
+        break;
+    }
+
     default:
         rc = -EOPNOTSUPP;
         break;
diff --git a/xen/include/public/argo.h b/xen/include/public/argo.h
index e73faea..24696e2 100644
--- a/xen/include/public/argo.h
+++ b/xen/include/public/argo.h
@@ -138,4 +138,16 @@ struct xen_argo_ring_message_header
 /* Mask for all defined flags. unsigned long type so ok for both 32/64-bit */
 #define XEN_ARGO_REGISTER_FLAG_MASK 0x1UL
 
+/*
+ * XEN_ARGO_MESSAGE_OP_unregister_ring
+ *
+ * Unregister a previously-registered ring, ending communication.
+ *
+ * arg1: XEN_GUEST_HANDLE(xen_argo_ring_t)
+ * arg2: NULL
+ * arg3: 0 (ZERO)
+ * arg4: 0 (ZERO)
+ */
+#define XEN_ARGO_MESSAGE_OP_unregister_ring     2
+
 #endif
-- 
2.7.4


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