iommu/vt-d: Tylersburg isoch identity map check is done too late.

BugLink: http://bugs.launchpad.net/bugs/1673538

commit 21e722c4 upstream.

The check to set identity map for tylersburg is done too late. It needs
to be done before the check for identity_map domain is done.

To: Joerg Roedel <joro@8bytes.org>
To: David Woodhouse <dwmw2@infradead.org>
Cc: iommu@lists.linux-foundation.org
Cc: linux-kernel@vger.kernel.org
Cc: Ashok Raj <ashok.raj@intel.com>

Fixes: 86080ccc ("iommu/vt-d: Allocate si_domain in init_dmars()")
Signed-off-by: Ashok Raj <ashok.raj@intel.com>
Reported-by: Yunhong Jiang <yunhong.jiang@intel.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>

drivers/iommu/intel-iommu.c

@@ -3238,13 +3238,14 @@ static int __init init_dmars(void)
 	iommu_identity_mapping |= IDENTMAP_GFX;
 #endif
 
+	check_tylersburg_isoch();
+
 	if (iommu_identity_mapping) {
 		ret = si_domain_init(hw_pass_through);
 		if (ret)
 			goto free_iommu;
 	}
 
-	check_tylersburg_isoch();
 
 	/*
 	 * If we copied translations from a previous kernel in the kdump