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

From: Janne Grunau
Date: Fri Sep 16 2022 - 05:42:08 EST


From: Sven Peter <sven@xxxxxxxxxxxxx>

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@xxxxxxxxxxxxx>
Signed-off-by: Janne Grunau <j@xxxxxxxxxx>

---

(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