iommu/vt-d: Fix infinite loop in free_all_cpu_cached_iovas

Per VT-d spec Section 10.4.2 ("Capability Register"), the maximum
number of possible domains is 64K; indeed this is the maximum value
that the cap_ndoms() macro will expand to.  Since the value 65536
will not fix in a u16, the 'did' variable must be promoted to an
int, otherwise the test for < 65536 will always be true and the
loop will never end.

The symptom, in my case, was a hung machine during suspend.

Fixes: 3bd4f911 ("iommu/vt-d: Fix overflow of iommu->domains array")
Signed-off-by: Aaron Campbell <aaron@monkey.org>
Signed-off-by: Joerg Roedel <jroedel@suse.de>

drivers/iommu/intel-iommu.c

@@ -4602,13 +4602,13 @@ static void free_all_cpu_cached_iovas(unsigned int cpu)
 	for (i = 0; i < g_num_of_iommus; i++) {
 		struct intel_iommu *iommu = g_iommus[i];
 		struct dmar_domain *domain;
-		u16 did;
+		int did;
 
 		if (!iommu)
 			continue;
 
 		for (did = 0; did < cap_ndoms(iommu->cap); did++) {
-			domain = get_iommu_domain(iommu, did);
+			domain = get_iommu_domain(iommu, (u16)did);
 
 			if (!domain)
 				continue;