iommu/vt-d: Avoid calling virt_to_phys() on null pointer

New kernels with debug show panic() from __phys_addr() checks. Avoid
calling virt_to_phys()  when pasid_state_tbl pointer is null

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

Fixes: 2f26e0a9c9860 ('iommu/vt-d: Add basic SVM PASID support')
Signed-off-by: Ashok Raj <ashok.raj@intel.com>
Acked-by: David Woodhouse <dwmw@amazon.co.uk>
Signed-off-by: Joerg Roedel <jroedel@suse.de>

drivers/iommu/intel-iommu.c

@@ -5349,7 +5349,8 @@ int intel_iommu_enable_pasid(struct intel_iommu *iommu, struct intel_svm_dev *sd
 	sdev->sid = PCI_DEVID(info->bus, info->devfn);
 
 	if (!(ctx_lo & CONTEXT_PASIDE)) {
-		context[1].hi = (u64)virt_to_phys(iommu->pasid_state_table);
+		if (iommu->pasid_state_table)
+			context[1].hi = (u64)virt_to_phys(iommu->pasid_state_table);
 		context[1].lo = (u64)virt_to_phys(iommu->pasid_table) |
 			intel_iommu_get_pts(iommu);