intel-iommu: Flush unmaps at domain_exit

Backported Alex Williamson's commit to 2.6.32.y
http://git.kernel.org/linus/7b668357810ecb5fdda4418689d50f5d95aea6a8

It resolves the following assert when module is immediately reloaded.

kernel BUG at drivers/pci/iova.c:155!
<snip>
Call Trace:
[<ffffffff812645c5>] intel_alloc_iova+0xb5/0xe0
[<ffffffff8126725e>] __intel_map_single+0xbe/0x210
[<ffffffff812674ae>] intel_alloc_coherent+0xae/0x120
[<ffffffffa035f909>] be_queue_alloc+0xb9/0x140 [be2net]
[<ffffffffa035fa5a>] be_rx_qs_create+0xca/0x370 [be2net]
<snip>

The issue is reproducible in 2.6.32.60 and also gets resolved
by passing intel-iommu=strict to kernel.
Signed-off-by: Jitendra Bhivare <jitendra.bhivare@gmail.com>
Signed-off-by: Willy Tarreau <w@1wt.eu>

drivers/pci/intel-iommu.c

@@ -1434,6 +1434,10 @@ static void domain_exit(struct dmar_domain *domain)
 	if (!domain)
 		return;
 
+	/* Flush any lazy unmaps that may reference this domain */
+	if (!intel_iommu_strict)
+		flush_unmaps_timeout(0);
+
 	domain_remove_dev_info(domain);
 	/* destroy iovas */
 	put_iova_domain(&domain->iovad);