[PATCH 6.1 122/181] iommu/vt-d: Allow zero SAGAW if second-stage not supported

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From: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>

[ Upstream commit bfd3c6b9fa4a1dc78139dd1621d5bea321ffa69d ]

The VT-d spec states (in section 11.4.2) that hardware implementations
reporting second-stage translation support (SSTS) field as Clear also
report the SAGAW field as 0. Fix an inappropriate check in alloc_iommu().

Fixes: 792fb43ce2c9 ("iommu/vt-d: Enable Intel IOMMU scalable mode by default")
Suggested-by: Raghunathan Srinivasan <raghunathan.srinivasan@xxxxxxxxx>
Reviewed-by: Kevin Tian <kevin.tian@xxxxxxxxx>
Signed-off-by: Jacob Pan <jacob.jun.pan@xxxxxxxxxxxxxxx>
Signed-off-by: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/20230318024824.124542-1-baolu.lu@xxxxxxxxxxxxxxx
Link: https://lore.kernel.org/r/20230329134721.469447-3-baolu.lu@xxxxxxxxxxxxxxx
Signed-off-by: Joerg Roedel <jroedel@xxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 drivers/iommu/intel/dmar.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/iommu/intel/dmar.c b/drivers/iommu/intel/dmar.c
index bc94059a5b870..f800989ea0462 100644
--- a/drivers/iommu/intel/dmar.c
+++ b/drivers/iommu/intel/dmar.c
@@ -1057,7 +1057,8 @@ static int alloc_iommu(struct dmar_drhd_unit *drhd)
 	}
 
 	err = -EINVAL;
-	if (cap_sagaw(iommu->cap) == 0) {
+	if (!cap_sagaw(iommu->cap) &&
+	    (!ecap_smts(iommu->ecap) || ecap_slts(iommu->ecap))) {
 		pr_info("%s: No supported address widths. Not attempting DMA translation.\n",
 			iommu->name);
 		drhd->ignored = 1;
-- 
2.39.2






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