[PATCH 2/2] iommu/vt-d: Set SRE bit only when hardware has SRS cap

[Lu Baolu]

From: Tina Zhang <tina.zhang@xxxxxxxxx>

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: stable@xxxxxxxxxxxxxxx
Signed-off-by: Tina Zhang <tina.zhang@xxxxxxxxx>
Link: https://lore.kernel.org/r/20221115070346.1112273-1-tina.zhang@xxxxxxxxx
Signed-off-by: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>
---
 drivers/iommu/intel/pasid.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/iommu/intel/pasid.c b/drivers/iommu/intel/pasid.c
index c30ddac40ee5..e13d7e5273e1 100644
--- a/drivers/iommu/intel/pasid.c
+++ b/drivers/iommu/intel/pasid.c
@@ -642,7 +642,7 @@ int intel_pasid_setup_second_level(struct intel_iommu *iommu,
 	 * 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);
@@ -685,7 +685,8 @@ int intel_pasid_setup_pass_through(struct intel_iommu *iommu,
 	 * 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);
 
-- 
2.34.1