[PATCH RFC 37/39] xen-netback: xen_shim_domain() support

[Joao Martins]

GNTTABOP_map_grant_ref treats host_address as an OUT parameter for
xen_shim_domain(). After doing gnttab_map_refs, we check each map op
struct and replace the page passed with the page returned by the
hypercall.

Note that mmap_pages is just a placeholder when netback runs in
xen_shim_domain() mode.

Signed-off-by: Joao Martins <joao.m.mart...@oracle.com>
---
 drivers/net/xen-netback/netback.c | 25 +++++++++++++++++++++----
 1 file changed, 21 insertions(+), 4 deletions(-)

diff --git a/drivers/net/xen-netback/netback.c 
b/drivers/net/xen-netback/netback.c
index 80aae3a32c2a..a5dd6de6d3e6 100644
--- a/drivers/net/xen-netback/netback.c
+++ b/drivers/net/xen-netback/netback.c
@@ -324,6 +324,9 @@ struct xenvif_tx_cb {
 
 #define XENVIF_TX_CB(skb) ((struct xenvif_tx_cb *)(skb)->cb)
 
+/* Selects host map only if on native Xen */
+#define GNTTAB_host_map (xen_shim_domain() ? 0 : GNTMAP_host_map)
+
 static inline void xenvif_tx_create_map_op(struct xenvif_queue *queue,
                                           u16 pending_idx,
                                           struct xen_netif_tx_request *txp,
@@ -332,9 +335,12 @@ static inline void xenvif_tx_create_map_op(struct 
xenvif_queue *queue,
 {
        queue->pages_to_map[mop-queue->tx_map_ops] = 
queue->mmap_pages[pending_idx];
        gnttab_set_map_op(mop, idx_to_kaddr(queue, pending_idx),
-                         GNTMAP_host_map | GNTMAP_readonly,
+                         GNTTAB_host_map | GNTMAP_readonly,
                          txp->gref, queue->vif->domid);
 
+       if (xen_shim_domain())
+               mop->host_addr = 0;
+
        memcpy(&queue->pending_tx_info[pending_idx].req, txp,
               sizeof(*txp));
        queue->pending_tx_info[pending_idx].extra_count = extra_count;
@@ -405,6 +411,12 @@ static struct gnttab_map_grant_ref 
*xenvif_get_requests(struct xenvif_queue *que
        return gop;
 }
 
+static inline void xenvif_grant_replace_page(struct xenvif_queue *queue,
+                                            u16 pending_idx, u32 mapping_idx)
+{
+       queue->mmap_pages[pending_idx] = queue->pages_to_map[mapping_idx];
+}
+
 static inline void xenvif_grant_handle_set(struct xenvif_queue *queue,
                                           u16 pending_idx,
                                           grant_handle_t handle)
@@ -481,6 +493,10 @@ static int xenvif_tx_check_gop(struct xenvif_queue *queue,
                        xenvif_grant_handle_set(queue,
                                                pending_idx,
                                                gop_map->handle);
+
+                       if (!err && xen_shim_domain())
+                               xenvif_grant_replace_page(queue, pending_idx,
+                                                   gop_map - 
queue->tx_map_ops);
                        /* Had a previous error? Invalidate this fragment. */
                        if (unlikely(err)) {
                                xenvif_idx_unmap(queue, pending_idx);
@@ -1268,7 +1284,7 @@ static inline void xenvif_tx_dealloc_action(struct 
xenvif_queue *queue)
                                queue->mmap_pages[pending_idx];
                        gnttab_set_unmap_op(gop,
                                            idx_to_kaddr(queue, pending_idx),
-                                           GNTMAP_host_map,
+                                           GNTTAB_host_map,
                                            
queue->grant_tx_handle[pending_idx]);
                        xenvif_grant_handle_reset(queue, pending_idx);
                        ++gop;
@@ -1394,7 +1410,7 @@ void xenvif_idx_unmap(struct xenvif_queue *queue, u16 
pending_idx)
 
        gnttab_set_unmap_op(&tx_unmap_op,
                            idx_to_kaddr(queue, pending_idx),
-                           GNTMAP_host_map,
+                           GNTTAB_host_map,
                            queue->grant_tx_handle[pending_idx]);
        xenvif_grant_handle_reset(queue, pending_idx);
 
@@ -1622,7 +1638,7 @@ static int __init netback_init(void)
 {
        int rc = 0;
 
-       if (!xen_domain())
+       if (!xen_domain() && !xen_shim_domain_get())
                return -ENODEV;
 
        /* Allow as many queues as there are CPUs but max. 8 if user has not
@@ -1663,6 +1679,7 @@ static void __exit netback_fini(void)
        debugfs_remove_recursive(xen_netback_dbg_root);
 #endif /* CONFIG_DEBUG_FS */
        xenvif_xenbus_fini();
+       xen_shim_domain_put();
 }
 module_exit(netback_fini);
 
-- 
2.11.0