linux-kernel - [PATCH v5 3/5] iommu/io-pgtable: Add DART subpage protection support

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Date:   Fri, 16 Sep 2022 11:41:50 +0200
From:   Janne Grunau <j@...nau.net>
To:     iommu@...ts.linux.dev
Cc:     Konrad Dybcio <konrad.dybcio@...ainline.org>,
        asahi@...ts.linux.dev, Sven Peter <sven@...npeter.dev>,
        Alyssa Rosenzweig <alyssa@...enzweig.io>,
        Hector Martin <marcan@...can.st>,
        Joerg Roedel <joro@...tes.org>, Will Deacon <will@...nel.org>,
        iommu@...ts.linux-foundation.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: [PATCH v5 3/5] iommu/io-pgtable: Add DART subpage protection support

From: Sven Peter <sven@...npeter.dev>

DART allows to only expose a subpage to the device. While this is an
optional feature on the M1 DARTs the new ones present on the Pro/Max
models require this field in every PTE.

Signed-off-by: Sven Peter <sven@...npeter.dev>
Signed-off-by: Janne Grunau <j@...nau.net>

---

(no changes since v3)

Changes in v3:
- apply change to io-pgtable-dart.c

 drivers/iommu/io-pgtable-dart.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/drivers/iommu/io-pgtable-dart.c b/drivers/iommu/io-pgtable-dart.c
index 312d40528748..665a52e5c9b0 100644
--- a/drivers/iommu/io-pgtable-dart.c
+++ b/drivers/iommu/io-pgtable-dart.c
@@ -14,6 +14,7 @@
 #define pr_fmt(fmt)	"dart io-pgtable: " fmt
 
 #include <linux/atomic.h>
+#include <linux/bitfield.h>
 #include <linux/bitops.h>
 #include <linux/io-pgtable.h>
 #include <linux/kernel.h>
@@ -40,6 +41,9 @@
 #define DART_PTES_PER_TABLE(d)					\
 	(DART_GRANULE(d) >> ilog2(sizeof(dart_iopte)))
 
+#define APPLE_DART_PTE_SUBPAGE_START   GENMASK_ULL(63, 52)
+#define APPLE_DART_PTE_SUBPAGE_END     GENMASK_ULL(51, 40)
+
 #define APPLE_DART1_PADDR_MASK	GENMASK_ULL(35, 12)
 
 /* Apple DART1 protection bits */
@@ -108,6 +112,10 @@ static int dart_init_pte(struct dart_io_pgtable *data,
 			return -EEXIST;
 		}
 
+	/* subpage protection: always allow access to the entire page */
+	pte |= FIELD_PREP(APPLE_DART_PTE_SUBPAGE_START, 0);
+	pte |= FIELD_PREP(APPLE_DART_PTE_SUBPAGE_END, 0xfff);
+
 	pte |= APPLE_DART1_PTE_PROT_SP_DIS;
 	pte |= APPLE_DART_PTE_VALID;
 
-- 
2.35.1