[Xen-changelog] [qemu-upstream-unstable] qemu/xendisk: set maximum number of grants to be used

[patchbot@xxxxxxx]

commit f7f8c33cd49885d69efc2e5f7f9a613d631762e2
Author: Jan Beulich <JBeulich@xxxxxxxx>
Date:   Wed Jun 13 10:45:07 2012 +0000

    qemu/xendisk: set maximum number of grants to be used
    
    Legacy (non-pvops) gntdev drivers may require this to be done when the
    number of grants intended to be used simultaneously exceeds a certain
    driver specific default limit.
    
    upstream-commit: 64c27e5b1fdb6d94bdc0bda3b1869d7383a35c65
    
    Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
    Signed-off-by: Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>
---
 hw/xen_disk.c |   14 ++++++++++++++
 1 files changed, 14 insertions(+), 0 deletions(-)

diff --git a/hw/xen_disk.c b/hw/xen_disk.c
index a76cd73..88544b1 100644
--- a/hw/xen_disk.c
+++ b/hw/xen_disk.c
@@ -534,6 +534,15 @@ static void blk_bh(void *opaque)
     blk_handle_requests(blkdev);
 }
 
+/*
+ * We need to account for the grant allocations requiring contiguous
+ * chunks; the worst case number would be
+ *     max_req * max_seg + (max_req - 1) * (max_seg - 1) + 1,
+ * but in order to keep things simple just use
+ *     2 * max_req * max_seg.
+ */
+#define MAX_GRANTS(max_req, max_seg) (2 * (max_req) * (max_seg))
+
 static void blk_alloc(struct XenDevice *xendev)
 {
     struct XenBlkDev *blkdev = container_of(xendev, struct XenBlkDev, xendev);
@@ -545,6 +554,11 @@ static void blk_alloc(struct XenDevice *xendev)
     if (xen_mode != XEN_EMULATE) {
         batch_maps = 1;
     }
+    if (xc_gnttab_set_max_grants(xendev->gnttabdev,
+            MAX_GRANTS(max_requests, BLKIF_MAX_SEGMENTS_PER_REQUEST)) < 0) {
+        xen_be_printf(xendev, 0, "xc_gnttab_set_max_grants failed: %s\n",
+                      strerror(errno));
+    }
 }
 
 static int blk_init(struct XenDevice *xendev)
--
generated by git-patchbot for /home/xen/git/qemu-upstream-unstable.git

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