[Xen-devel] [PATCH v5 08/15] argo: implement the unregister op

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

Takes a single argument: a handle to the ring unregistration struct,
which specifies the port and partner domain id or wildcard.

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.

If the ring had been registered to communicate with a single specified
domain (ie. a non-wildcard ring) then the partner domain state is removed
from the partner domain's argo send_info hash table.

Signed-off-by: Christopher Clark <christopher.clark6@xxxxxxxxxxxxxx>
---
The logic in unregister_ring got pretty heavily reordered in this version
of the patch, to shrink the critical sections. I'm happy with the result.
I've added a couple of ASSERT_UNREACHABLEs where it seems appropriate.

v4 # Jan: shrink the critical sections in unregister
v4 : use standard data structures as per common code
v4 #08 Roger: skip send_info lookup for wildcard rings
v4: add ASSERT_UNREACHABLE for missing sender domain or send_info
v4: reduce indentation by using goto
v4: add unlikely to currd->argo check
v4 #08 Jan: move put_domain outside L2 critical section
v4: include ring data in debug output when ring not found

v3 #08 Jan: pull xfree out of exclusive critical sections in unregister_ring
v3 #08 Jan: rename send_find_info to find_send_info
v3 #07 Jan: rename ring_find_info to find_ring_info
v3 #08 Roger: use return and remove the out label in unregister_ring
v3 #08 Roger: better debug output in send_find_info
v3 #10 Roger: move find functions to top of file and drop prototypes
v3 #04 Jan: meld compat check for unregister_ring struct
v3 #04 Roger/Jan: make lock names clearer and assert their state
v3 #04 Jan: port -> aport with type; distinguish argo port from evtchn
v3 feedback Roger/Jan: ASSERT currd is current->domain or use 'd' variable name
v3 feedback #07 Roger: const the argo_ring_id structs in send_find_info
v2 feedback Jan: drop cookie, implement teardown
v2 feedback Jan: drop message from argo_message_op
v2 self: OVERHAUL
v2 self: reorder logic to shorten critical section
v1 #13 feedback Jan: revise use of guest_handle_okay vs __copy ops
v1 feedback Roger, Jan: drop argo prefix on static functions
v1,2 feedback Jan/Roger/Paul: drop errno returning guest access functions
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         | 126 ++++++++++++++++++++++++++++++++++++++++++++++
 xen/common/compat/argo.c  |   1 +
 xen/include/public/argo.h |  19 +++++++
 xen/include/xlat.lst      |   1 +
 4 files changed, 147 insertions(+)

diff --git a/xen/common/argo.c b/xen/common/argo.c
index a7ec0e0..e4cd446 100644
--- a/xen/common/argo.c
+++ b/xen/common/argo.c
@@ -43,6 +43,7 @@ DEFINE_XEN_GUEST_HANDLE(xen_argo_addr_t);
 DEFINE_XEN_GUEST_HANDLE(xen_argo_gfn_t);
 DEFINE_XEN_GUEST_HANDLE(xen_argo_register_ring_t);
 DEFINE_XEN_GUEST_HANDLE(xen_argo_ring_t);
+DEFINE_XEN_GUEST_HANDLE(xen_argo_unregister_ring_t);
 
 static bool __read_mostly opt_argo;
 static bool __read_mostly opt_argo_mac_permissive;
@@ -351,6 +352,37 @@ find_ring_info(const struct domain *d, const struct 
argo_ring_id *id)
     return NULL;
 }
 
+static struct argo_send_info *
+find_send_info(const struct domain *d, const struct argo_ring_id *id)
+{
+    struct list_head *cursor, *bucket;
+
+    ASSERT(LOCKING_send_L2(d));
+
+    /* List is not modified here. Search and return the match if found. */
+    bucket = &d->argo->send_hash[hash_index(id)];
+
+    for ( cursor = bucket->next; cursor != bucket; cursor = cursor->next )
+    {
+        struct argo_send_info *send_info =
+            list_entry(cursor, struct argo_send_info, node);
+        const struct argo_ring_id *cmpid = &send_info->id;
+
+        if ( cmpid->aport == id->aport &&
+             cmpid->domain_id == id->domain_id &&
+             cmpid->partner_id == id->partner_id )
+        {
+            argo_dprintk("found send_info for ring(%u:%x %u)\n",
+                         id->domain_id, id->aport, id->partner_id);
+            return send_info;
+        }
+    }
+    argo_dprintk("no send_info for ring(%u:%x %u)\n",
+                 id->domain_id, id->aport, id->partner_id);
+
+    return NULL;
+}
+
 static void
 ring_unmap(const struct domain *d, struct argo_ring_info *ring_info)
 {
@@ -735,6 +767,85 @@ find_ring_mfns(struct domain *d, struct argo_ring_info 
*ring_info,
 }
 
 static long
+unregister_ring(struct domain *currd,
+                XEN_GUEST_HANDLE_PARAM(xen_argo_unregister_ring_t) unreg_hnd)
+{
+    xen_argo_unregister_ring_t unreg;
+    struct argo_ring_id ring_id;
+    struct argo_ring_info *ring_info = NULL;
+    struct argo_send_info *send_info = NULL;
+    struct domain *dst_d = NULL;
+
+    ASSERT(currd == current->domain);
+
+    if ( copy_from_guest(&unreg, unreg_hnd, 1) )
+        return -EFAULT;
+
+    if ( unreg.pad )
+        return -EINVAL;
+
+    ring_id.partner_id = unreg.partner_id;
+    ring_id.aport = unreg.aport;
+    ring_id.domain_id = currd->domain_id;
+
+    read_lock(&L1_global_argo_rwlock);
+
+    if ( unlikely(!currd->argo) )
+    {
+        read_unlock(&L1_global_argo_rwlock);
+        return -ENODEV;
+    }
+
+    write_lock(&currd->argo->rings_L2_rwlock);
+
+    ring_info = find_ring_info(currd, &ring_id);
+    if ( !ring_info )
+        goto out;
+
+    ring_remove_info(currd, ring_info);
+    currd->argo->ring_count--;
+
+    if ( ring_id.partner_id == XEN_ARGO_DOMID_ANY )
+        goto out;
+
+    dst_d = get_domain_by_id(ring_id.partner_id);
+    if ( !dst_d || !dst_d->argo )
+    {
+        ASSERT_UNREACHABLE();
+        goto out;
+    }
+
+    spin_lock(&dst_d->argo->send_L2_lock);
+
+    send_info = find_send_info(dst_d, &ring_id);
+    if ( send_info )
+        list_del(&send_info->node);
+    else
+        ASSERT_UNREACHABLE();
+
+    spin_unlock(&dst_d->argo->send_L2_lock);
+
+ out:
+    write_unlock(&currd->argo->rings_L2_rwlock);
+
+    read_unlock(&L1_global_argo_rwlock);
+
+    if ( dst_d )
+        put_domain(dst_d);
+
+    xfree(send_info);
+
+    if ( !ring_info )
+    {
+        argo_dprintk("unregister_ring: no ring_info found for ring(%u:%x 
%u)\n",
+                     ring_id.domain_id, ring_id.aport, ring_id.partner_id);
+        return -ENOENT;
+    }
+
+    return 0;
+}
+
+static long
 register_ring(struct domain *currd,
               XEN_GUEST_HANDLE_PARAM(xen_argo_register_ring_t) reg_hnd,
               XEN_GUEST_HANDLE_PARAM(xen_argo_gfn_t) gfn_hnd,
@@ -1019,6 +1130,21 @@ do_argo_op(unsigned int cmd, 
XEN_GUEST_HANDLE_PARAM(void) arg1,
         break;
     }
 
+    case XEN_ARGO_OP_unregister_ring:
+    {
+        XEN_GUEST_HANDLE_PARAM(xen_argo_unregister_ring_t) unreg_hnd =
+            guest_handle_cast(arg1, xen_argo_unregister_ring_t);
+
+        if ( unlikely((!guest_handle_is_null(arg2)) || arg3 || arg4) )
+        {
+            rc = -EINVAL;
+            break;
+        }
+
+        rc = unregister_ring(currd, unreg_hnd);
+        break;
+    }
+
     default:
         rc = -EOPNOTSUPP;
         break;
diff --git a/xen/common/compat/argo.c b/xen/common/compat/argo.c
index 9437a7a..6a1671c 100644
--- a/xen/common/compat/argo.c
+++ b/xen/common/compat/argo.c
@@ -22,3 +22,4 @@
 CHECK_argo_addr;
 CHECK_argo_register_ring;
 CHECK_argo_ring;
+CHECK_argo_unregister_ring;
diff --git a/xen/include/public/argo.h b/xen/include/public/argo.h
index f822756..2371510 100644
--- a/xen/include/public/argo.h
+++ b/xen/include/public/argo.h
@@ -79,6 +79,13 @@ typedef struct xen_argo_register_ring
     uint32_t len;
 } xen_argo_register_ring_t;
 
+typedef struct xen_argo_unregister_ring
+{
+    xen_argo_port_t aport;
+    domid_t partner_id;
+    uint16_t pad;
+} xen_argo_unregister_ring_t;
+
 /* Messages on the ring are padded to a multiple of this size. */
 #define XEN_ARGO_MSG_SLOT_SIZE 0x10
 
@@ -134,4 +141,16 @@ struct xen_argo_ring_message_header
 #define XEN_ARGO_REGISTER_FLAG_MASK XEN_ARGO_REGISTER_FLAG_FAIL_EXIST
 #endif
 
+/*
+ * XEN_ARGO_OP_unregister_ring
+ *
+ * Unregister a previously-registered ring, ending communication.
+ *
+ * arg1: XEN_GUEST_HANDLE(xen_argo_unregister_ring_t)
+ * arg2: NULL
+ * arg3: 0 (ZERO)
+ * arg4: 0 (ZERO)
+ */
+#define XEN_ARGO_OP_unregister_ring     2
+
 #endif
diff --git a/xen/include/xlat.lst b/xen/include/xlat.lst
index 9c9d33f..411c661 100644
--- a/xen/include/xlat.lst
+++ b/xen/include/xlat.lst
@@ -151,3 +151,4 @@
 ?      argo_addr                       argo.h
 ?      argo_ring                       argo.h
 ?      argo_register_ring              argo.h
+?      argo_unregister_ring            argo.h
-- 
2.7.4


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