iommu/vt-d: Set SRE bit only when hardware has SRS cap

SRS cap is the hardware cap telling if the hardware IOMMU can support
requests seeking supervisor privilege or not. SRE bit in scalable-mode
PASID table entry is treated as Reserved(0) for implementation not
supporting SRS cap.

Checking SRS cap before setting SRE bit can avoid the non-recoverable
fault of "Non-zero reserved field set in PASID Table Entry" caused by
setting SRE bit while there is no SRS cap support. The fault messages
look like below:

DMAR: DRHD: handling fault status reg 2
DMAR: [DMA Read NO_PASID] Request device [00:0d.0] fault addr 0x1154e1000
[fault reason 0x5a]
SM: Non-zero reserved field set in PASID Table Entry

Fixes: 6f7db75e1c46 ("iommu/vt-d: Add second level page table interface")
Cc: [e-mail]
Signed-off-by: Tina Zhang <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Lu Baolu <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Joerg Roedel <[e-mail]>

drivers/iommu/intel/pasid.c

···
 	 * Since it is a second level only translation setup, we should
 	 * set SRE bit as well (addresses are expected to be GPAs).
 	 */
-	if (pasid != PASID_RID2PASID)
+	if (pasid != PASID_RID2PASID && ecap_srs(iommu->ecap))
 		pasid_set_sre(pte);
 	pasid_set_present(pte);
 	spin_unlock(&iommu->lock);
···
 	 * We should set SRE bit as well since the addresses are expected
 	 * to be GPAs.
 	 */
-	pasid_set_sre(pte);
+	if (ecap_srs(iommu->ecap))
+		pasid_set_sre(pte);
 	pasid_set_present(pte);
 	spin_unlock(&iommu->lock);