path: root/drivers/xen/xenbus
diff options
authorAndres Lagar-Cavilla <andres@lagarcavilla.org>2012-09-14 14:26:59 +0000
committerKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>2012-09-21 09:23:51 -0400
commitc571898ffc24a1768e1b2dabeac0fc7dd4c14601 (patch)
tree65070baf01dd31aecfb9c15d2a3c1fa20fdba0da /drivers/xen/xenbus
parentc3cb4709809e655a4ba5a716086c8bc5bbbbccdb (diff)
xen/gndev: Xen backend support for paged out grant targets V4.
Since Xen-4.2, hvm domains may have portions of their memory paged out. When a foreign domain (such as dom0) attempts to map these frames, the map will initially fail. The hypervisor returns a suitable errno, and kicks an asynchronous page-in operation carried out by a helper. The foreign domain is expected to retry the mapping operation until it eventually succeeds. The foreign domain is not put to sleep because itself could be the one running the pager assist (typical scenario for dom0). This patch adds support for this mechanism for backend drivers using grant mapping and copying operations. Specifically, this covers the blkback and gntdev drivers (which map foreign grants), and the netback driver (which copies foreign grants). * Add a retry method for grants that fail with GNTST_eagain (i.e. because the target foreign frame is paged out). * Insert hooks with appropriate wrappers in the aforementioned drivers. The retry loop is only invoked if the grant operation status is GNTST_eagain. It guarantees to leave a new status code different from GNTST_eagain. Any other status code results in identical code execution as before. The retry loop performs 256 attempts with increasing time intervals through a 32 second period. It uses msleep to yield while waiting for the next retry. V2 after feedback from David Vrabel: * Explicit MAX_DELAY instead of wrap-around delay into zero * Abstract GNTST_eagain check into core grant table code for netback module. V3 after feedback from Ian Campbell: * Add placeholder in array of grant table error descriptions for unrelated error code we jump over. * Eliminate single map and retry macro in favor of a generic batch flavor. * Some renaming. * Bury most implementation in grant_table.c, cleaner interface. V4 rebased on top of sync of Xen grant table interface headers. Signed-off-by: Andres Lagar-Cavilla <andres@lagarcavilla.org> Acked-by: Ian Campbell <ian.campbell@citrix.com> [v5: Fixed whitespace issues] Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Diffstat (limited to 'drivers/xen/xenbus')
1 files changed, 2 insertions, 4 deletions
diff --git a/drivers/xen/xenbus/xenbus_client.c b/drivers/xen/xenbus/xenbus_client.c
index b3e146edb51..bcf3ba4a6ec 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) {
@@ -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,
- 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,