iommu/vt-d: Really use upper context table when necessary

There is a bug in iommu_context_addr() which will always use
the lower context table, even when the upper context table
needs to be used. Fix this issue.

Fixes: 03ecc32c ("iommu/vt-d: support extended root and context entries")
Reported-by: Xiao, Nan <nan.xiao@hp.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>

drivers/iommu/intel-iommu.c

@@ -803,6 +803,7 @@ static inline struct context_entry *iommu_context_addr(struct intel_iommu *iommu
 	struct context_entry *context;
 	u64 *entry;
 
+	entry = &root->lo;
 	if (ecs_enabled(iommu)) {
 		if (devfn >= 0x80) {
 			devfn -= 0x80;
@@ -810,7 +811,6 @@ static inline struct context_entry *iommu_context_addr(struct intel_iommu *iommu
 		}
 		devfn *= 2;
 	}
-	entry = &root->lo;
 	if (*entry & 1)
 		context = phys_to_virt(*entry & VTD_PAGE_MASK);
 	else {