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qemu/xendisk: set maximum number of grants to be used

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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.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
This commit is contained in:
Jan Beulich 2012-06-11 09:52:27 +00:00 committed by Stefano Stabellini
parent 78260a5f08
commit 64c27e5b1f
1 changed files with 14 additions and 0 deletions
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14
hw/xen_disk.c
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@ -537,6 +537,15 @@ 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);
@ -548,6 +557,11 @@ 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)