4 files changed, 70 insertions, 12 deletions

diff --git a/drivers/net/xen-netback/netback.c b/drivers/net/xen-netback/netback.c
index 682633bfe00f..05593d882023 100644
--- a/drivers/net/xen-netback/netback.c
+++ b/drivers/net/xen-netback/netback.c
@@ -635,9 +635,7 @@ static void xen_netbk_rx_action(struct xen_netbk *netbk)
                 return;
 
         BUG_ON(npo.copy_prod > ARRAY_SIZE(netbk->grant_copy_op));
-        ret = HYPERVISOR_grant_table_op(GNTTABOP_copy, &netbk->grant_copy_op,
-                                        npo.copy_prod);
-        BUG_ON(ret != 0);
+        gnttab_batch_copy(netbk->grant_copy_op, npo.copy_prod);
 
         while ((skb = __skb_dequeue(&rxq)) != NULL) {
                 sco = (struct skb_cb_overlay *)skb->cb;
@@ -1460,18 +1458,15 @@ static void xen_netbk_tx_submit(struct xen_netbk *netbk)
 static void xen_netbk_tx_action(struct xen_netbk *netbk)
 {
         unsigned nr_gops;
-        int ret;
 
         nr_gops = xen_netbk_tx_build_gops(netbk);
 
         if (nr_gops == 0)
                 return;
-        ret = HYPERVISOR_grant_table_op(GNTTABOP_copy,
-                                        netbk->tx_copy_ops, nr_gops);
-        BUG_ON(ret);
 
-        xen_netbk_tx_submit(netbk);
+        gnttab_batch_copy(netbk->tx_copy_ops, nr_gops);
 
+        xen_netbk_tx_submit(netbk);
 }
 
 static void xen_netbk_idx_release(struct xen_netbk *netbk, u16 pending_idx)
diff --git a/drivers/xen/grant-table.c b/drivers/xen/grant-table.c
index eea81cf8a2a5..3a567b15600b 100644
--- a/drivers/xen/grant-table.c
+++ b/drivers/xen/grant-table.c
@@ -38,6 +38,7 @@
 #include <linux/vmalloc.h>
 #include <linux/uaccess.h>
 #include <linux/io.h>
+#include <linux/delay.h>
 #include <linux/hardirq.h>
 
 #include <xen/xen.h>
@@ -823,6 +824,52 @@ unsigned int gnttab_max_grant_frames(void)
 }
 EXPORT_SYMBOL_GPL(gnttab_max_grant_frames);
 
+/* Handling of paged out grant targets (GNTST_eagain) */
+#define MAX_DELAY 256
+static inline void
+gnttab_retry_eagain_gop(unsigned int cmd, void *gop, int16_t *status,
+                                                const char *func)
+{
+        unsigned delay = 1;
+
+        do {
+                BUG_ON(HYPERVISOR_grant_table_op(cmd, gop, 1));
+                if (*status == GNTST_eagain)
+                        msleep(delay++);
+        } while ((*status == GNTST_eagain) && (delay < MAX_DELAY));
+
+        if (delay >= MAX_DELAY) {
+                printk(KERN_ERR "%s: %s eagain grant\n", func, current->comm);
+                *status = GNTST_bad_page;
+        }
+}
+
+void gnttab_batch_map(struct gnttab_map_grant_ref *batch, unsigned count)
+{
+        struct gnttab_map_grant_ref *op;
+
+        if (HYPERVISOR_grant_table_op(GNTTABOP_map_grant_ref, batch, count))
+                BUG();
+        for (op = batch; op < batch + count; op++)
+                if (op->status == GNTST_eagain)
+                        gnttab_retry_eagain_gop(GNTTABOP_map_grant_ref, op,
+                                                &op->status, __func__);
+}
+EXPORT_SYMBOL_GPL(gnttab_batch_map);
+
+void gnttab_batch_copy(struct gnttab_copy *batch, unsigned count)
+{
+        struct gnttab_copy *op;
+
+        if (HYPERVISOR_grant_table_op(GNTTABOP_copy, batch, count))
+                BUG();
+        for (op = batch; op < batch + count; op++)
+                if (op->status == GNTST_eagain)
+                        gnttab_retry_eagain_gop(GNTTABOP_copy, op,
+                                                &op->status, __func__);
+}
+EXPORT_SYMBOL_GPL(gnttab_batch_copy);
+
 int gnttab_map_refs(struct gnttab_map_grant_ref *map_ops,
                     struct gnttab_map_grant_ref *kmap_ops,
                     struct page **pages, unsigned int count)
@@ -836,6 +883,12 @@ int gnttab_map_refs(struct gnttab_map_grant_ref *map_ops,
         if (ret)
                 return ret;
 
+        /* Retry eagain maps */
+        for (i = 0; i < count; i++)
+                if (map_ops[i].status == GNTST_eagain)
+                        gnttab_retry_eagain_gop(GNTTABOP_map_grant_ref, map_ops + i,
+                                                &map_ops[i].status, __func__);
+
         if (xen_feature(XENFEAT_auto_translated_physmap))
                 return ret;
 
diff --git a/drivers/xen/xenbus/xenbus_client.c b/drivers/xen/xenbus/xenbus_client.c
index b3e146edb51d..bcf3ba4a6ec1 100644
--- a/drivers/xen/xenbus/xenbus_client.c
+++ b/drivers/xen/xenbus/xenbus_client.c
@@ -490,8 +490,7 @@ static int xenbus_map_ring_valloc_pv(struct xenbus_device *dev,
 
         op.host_addr = arbitrary_virt_to_machine(pte).maddr;
 
-        if (HYPERVISOR_grant_table_op(GNTTABOP_map_grant_ref, &op, 1))
-                BUG();
+        gnttab_batch_map(&op, 1);
 
         if (op.status != GNTST_okay) {
                 free_vm_area(area);
@@ -572,8 +571,7 @@ int xenbus_map_ring(struct xenbus_device *dev, int gnt_ref,
         gnttab_set_map_op(&op, (unsigned long)vaddr, GNTMAP_host_map, gnt_ref,
                           dev->otherend_id);
 
-        if (HYPERVISOR_grant_table_op(GNTTABOP_map_grant_ref, &op, 1))
-                BUG();
+        gnttab_batch_map(&op, 1);
 
         if (op.status != GNTST_okay) {
                 xenbus_dev_fatal(dev, op.status,
diff --git a/include/xen/grant_table.h b/include/xen/grant_table.h
index 11e27c3af3cb..ba0d77529a29 100644
--- a/include/xen/grant_table.h
+++ b/include/xen/grant_table.h
@@ -189,4 +189,16 @@ int gnttab_map_refs(struct gnttab_map_grant_ref *map_ops,
 int gnttab_unmap_refs(struct gnttab_unmap_grant_ref *unmap_ops,
                       struct page **pages, unsigned int count, bool clear_pte);
 
+/* Perform a batch of grant map/copy operations. Retry every batch slot
+ * for which the hypervisor returns GNTST_eagain. This is typically due
+ * to paged out target frames.
+ *
+ * Will retry for 1, 2, ... 255 ms, i.e. 256 times during 32 seconds.
+ *
+ * Return value in each iand every status field of the batch guaranteed
+ * to not be GNTST_eagain.
+ */
+void gnttab_batch_map(struct gnttab_map_grant_ref *batch, unsigned count);
+void gnttab_batch_copy(struct gnttab_copy *batch, unsigned count);
+
 #endif /* __ASM_GNTTAB_H__ */