# HG changeset patch
# User yamahata@xxxxxxxxxxxxx
# Date 1187579719 -32400
# Node ID 61346fe0eba4572eae3be811f83e8e3a42dda675
# Parent  b5fdf02c38f4765697196f5fad5d1262f2c157f4
work around for xencomm memory reservation op.
- Xencomm has single page size limit caused by xencomm_alloc()/xencomm_free()
  so that we have to repeat the hypercall. This limitation can be removed.
- Even if the above limitation is removed, the hypercall with large number of
  extents may cause the soft lockup warning.
  In order to avoid the warning, we limit the number of extents and repeat
  the hypercall. If the following limit causes soft lockup warning,
  we should decrease this value.
PATCHNAME: repeat_memory_reservation_op

Signed-off-by: Isaku Yamahata <yamahata@xxxxxxxxxxxxx>

diff -r b5fdf02c38f4 -r 61346fe0eba4 arch/ia64/xen/xcom_privcmd.c
--- a/arch/ia64/xen/xcom_privcmd.c	Thu Aug 16 13:44:51 2007 -0600
+++ b/arch/ia64/xen/xcom_privcmd.c	Mon Aug 20 12:15:19 2007 +0900
@@ -377,6 +377,94 @@ xencomm_privcmd_acm_op(privcmd_hypercall
 }
 
 static int
+xencomm_privcmd_memory_reservation_op(privcmd_hypercall_t *hypercall)
+{
+	const unsigned long cmd = hypercall->arg[0];
+	int ret = 0;
+	xen_memory_reservation_t kern_op;
+	xen_memory_reservation_t __user *user_op;
+	struct xencomm_handle *desc = NULL;
+	struct xencomm_handle *desc_op;
+
+	user_op = (xen_memory_reservation_t __user *)hypercall->arg[1];
+	if (copy_from_user(&kern_op, user_op,
+			   sizeof(xen_memory_reservation_t)))
+		return -EFAULT;
+	desc_op = xencomm_map_no_alloc(&kern_op, sizeof(kern_op));
+
+	if (!xen_guest_handle(kern_op.extent_start)) {
+		ret = xencomm_arch_hypercall_memory_op(cmd, desc_op);
+		if (ret < 0)
+			return ret;
+	} else {
+		xen_ulong_t nr_done = 0;
+		xen_ulong_t nr_extents = kern_op.nr_extents;
+		void *addr = xen_guest_handle(kern_op.extent_start);
+			
+		/*
+		 * Work around.
+		 * - Xencomm has single page size limit caused
+		 *   by xencomm_alloc()/xencomm_free() so that
+		 *   we have to repeat the hypercall.
+		 *   This limitation can be removed.
+		 * - Even if the above limitation is removed,
+		 *   the hypercall with large number of extents 
+		 *   may cause the soft lockup warning.
+		 *   In order to avoid the warning, we limit
+		 *   the number of extents and repeat the hypercall.
+		 *   If the following limit causes soft lockup warning,
+		 *   we should decrease this value.
+		 */
+#define MEMORYOP_MAX_EXTENTS						\
+		(((((PAGE_SIZE - sizeof(struct xencomm_desc)) /		\
+		    sizeof(uint64_t)) - 2) * PAGE_SIZE) /		\
+		 sizeof(*xen_guest_handle(kern_op.extent_start)))
+
+		while (nr_extents > 0) {
+			xen_ulong_t nr_tmp = nr_extents;
+			if (nr_tmp > MEMORYOP_MAX_EXTENTS)
+				nr_tmp = MEMORYOP_MAX_EXTENTS;
+
+			kern_op.nr_extents = nr_tmp;
+			desc = xencomm_map
+				(addr + nr_done * sizeof(*xen_guest_handle(kern_op.extent_start)),
+				 nr_tmp * sizeof(*xen_guest_handle(kern_op.extent_start)));
+			if (addr != NULL && nr_tmp > 0 && desc == NULL)
+				return (nr_done > 0)? nr_done: -ENOMEM;
+
+			set_xen_guest_handle(kern_op.extent_start,
+					     (void *)desc);
+
+			ret = xencomm_arch_hypercall_memory_op(
+				cmd, desc_op);
+			xencomm_free(desc);
+			if (ret < 0)
+				return (nr_done > 0)? nr_done: ret;
+
+			nr_done += ret;
+			nr_extents -= ret;
+			if (ret < nr_tmp)
+				break;
+
+			/*
+			 * prevent softlock up message.
+			 * give cpu to soft lockup kernel thread.
+			 */
+			if (nr_extents > 0)
+				schedule();
+		}
+		ret = nr_done;
+		set_xen_guest_handle(kern_op.extent_start, addr);
+	}
+
+	if (copy_to_user(user_op, &kern_op,
+			 sizeof(xen_memory_reservation_t)))
+		return -EFAULT;
+
+	return ret;
+}
+
+static int
 xencomm_privcmd_memory_op(privcmd_hypercall_t *hypercall)
 {
 	const unsigned long cmd = hypercall->arg[0];
@@ -386,48 +474,7 @@ xencomm_privcmd_memory_op(privcmd_hyperc
 	case XENMEM_increase_reservation:
 	case XENMEM_decrease_reservation:
 	case XENMEM_populate_physmap:
-	{
-		xen_memory_reservation_t kern_op;
-		xen_memory_reservation_t __user *user_op;
-		struct xencomm_handle *desc = NULL;
-		struct xencomm_handle *desc_op;
-
-		user_op = (xen_memory_reservation_t __user *)hypercall->arg[1];
-		if (copy_from_user(&kern_op, user_op,
-		                   sizeof(xen_memory_reservation_t)))
-			return -EFAULT;
-		desc_op = xencomm_map_no_alloc(&kern_op, sizeof(kern_op));
-
-		if (xen_guest_handle(kern_op.extent_start)) {
-			void * addr;
-
-			addr = xen_guest_handle(kern_op.extent_start);
-			desc = xencomm_map
-				(addr,
-				 kern_op.nr_extents *
-				 sizeof(*xen_guest_handle
-					(kern_op.extent_start)));
-			if (addr != NULL && kern_op.nr_extents > 0 &&
-			    desc == NULL)
-				return -ENOMEM;
-
-			set_xen_guest_handle(kern_op.extent_start,
-			                     (void *)desc);
-		}
-
-		ret = xencomm_arch_hypercall_memory_op(cmd, desc_op);
-
-		xencomm_free(desc);
-
-		if (ret != 0)
-			return ret;
-
-		if (copy_to_user(user_op, &kern_op,
-		                 sizeof(xen_memory_reservation_t)))
-			return -EFAULT;
-
-		return ret;
-	}
+		return xencomm_privcmd_memory_reservation_op(hypercall);
 	case XENMEM_maximum_gpfn:
 	{
 		domid_t kern_domid;