linux-kernel - [PATCH 1/1] iommu/vt-d: Treat PAGE

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Message-ID: <20260205084941.3982847-2-baolu.lu@linux.intel.com>
Date: Thu,  5 Feb 2026 16:49:41 +0800
From: Lu Baolu <baolu.lu@...ux.intel.com>
To: Joerg Roedel <joro@...tes.org>
Cc: Viktor Kleen <viktor@...en.org>,
	iommu@...ts.linux.dev,
	linux-kernel@...r.kernel.org
Subject: [PATCH 1/1] iommu/vt-d: Treat PAGE_SNOOP and PWSNP separately

From: Viktor Kleen <viktor@...en.org>

The PASID_FLAG_PAGE_SNOOP and PASID_FLAG_PWSNP constants are identical.
This will cause the pasid code to always set both or neither of the
PGSNP and PWSNP bits in PASID table entries. However, PWSNP is a
reserved bit if SMPWC is not set in the IOMMU's extended capability
register, even if SC is supported.

This has resulted in DMAR errors when testing the iommufd code on an
Arrow Lake platform. With this patch, those errors disappear and the
PASID table entries look correct.

Fixes: 101a2854110fa ("iommu/vt-d: Follow PT_FEAT_DMA_INCOHERENT into the PASID entry")
Cc: stable@...r.kernel.org
Signed-off-by: Viktor Kleen <viktor@...en.org>
Reviewed-by: Jason Gunthorpe <jgg@...dia.com>
Link: https://lore.kernel.org/r/20260202192109.1665799-1-viktor@kleen.org
Signed-off-by: Lu Baolu <baolu.lu@...ux.intel.com>
---
 drivers/iommu/intel/pasid.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/iommu/intel/pasid.h b/drivers/iommu/intel/pasid.h
index c3c8c907983e..48d3bb6b68de 100644
--- a/drivers/iommu/intel/pasid.h
+++ b/drivers/iommu/intel/pasid.h
@@ -24,7 +24,7 @@
 
 #define PASID_FLAG_NESTED		BIT(1)
 #define PASID_FLAG_PAGE_SNOOP		BIT(2)
-#define PASID_FLAG_PWSNP		BIT(2)
+#define PASID_FLAG_PWSNP		BIT(3)
 
 /*
  * The PASID_FLAG_FL5LP flag Indicates using 5-level paging for first-
-- 
2.43.0