[PATCH 4/6] iommu/generic_pt: Add Broadcom BCM2712 page table format
Daniel Drake
dan at reactivated.net
Sun Jul 12 14:18:54 PDT 2026
The BCM2712 IOMMU implements a 2-level page table format. It is relatively
simple, with one unusual aspect: leaf entries can only be installed at
Level 0.
Adapted from Raspberry Pi's downstream bcm2712-iommu driver (original
author Nick Hollinghurst).
Signed-off-by: Daniel Drake <dan at reactivated.net>
---
drivers/iommu/generic_pt/.kunitconfig | 1 +
drivers/iommu/generic_pt/Kconfig | 10 ++
drivers/iommu/generic_pt/fmt/Makefile | 2 +
drivers/iommu/generic_pt/fmt/bcm2712.h | 259 +++++++++++++++++++++++++++
drivers/iommu/generic_pt/fmt/defs_bcm2712.h | 18 ++
drivers/iommu/generic_pt/fmt/iommu_bcm2712.c | 10 ++
include/linux/generic_pt/common.h | 7 +
include/linux/generic_pt/iommu.h | 13 ++
8 files changed, 320 insertions(+)
diff --git a/drivers/iommu/generic_pt/.kunitconfig b/drivers/iommu/generic_pt/.kunitconfig
index 0bb98fe581fe..a3da74328f12 100644
--- a/drivers/iommu/generic_pt/.kunitconfig
+++ b/drivers/iommu/generic_pt/.kunitconfig
@@ -7,6 +7,7 @@ CONFIG_IOMMU_PT_AMDV1=y
CONFIG_IOMMU_PT_VTDSS=y
CONFIG_IOMMU_PT_RISCV64=y
CONFIG_IOMMU_PT_X86_64=y
+CONFIG_IOMMU_PT_BCM2712=y
CONFIG_IOMMU_PT_KUNIT_TEST=y
CONFIG_IOMMUFD=y
diff --git a/drivers/iommu/generic_pt/Kconfig b/drivers/iommu/generic_pt/Kconfig
index f4ed1add58b7..5c01cebb365f 100644
--- a/drivers/iommu/generic_pt/Kconfig
+++ b/drivers/iommu/generic_pt/Kconfig
@@ -72,6 +72,16 @@ config IOMMU_PT_X86_64
Selected automatically by an IOMMU driver that uses this format.
+config IOMMU_PT_BCM2712
+ tristate "IOMMU page table for Broadcom BCM2712"
+ depends on !GENERIC_ATOMIC64 # for cmpxchg64
+ help
+ iommu_domain implementation for the Broadcom BCM2712 IOMMU found on
+ Raspberry Pi 5. It supports 4K page sizes over a 2-level page table
+ format.
+
+ Selected automatically by an IOMMU driver that uses this format.
+
config IOMMU_PT_KUNIT_TEST
tristate "IOMMU Page Table KUnit Test" if !KUNIT_ALL_TESTS
depends on KUNIT
diff --git a/drivers/iommu/generic_pt/fmt/Makefile b/drivers/iommu/generic_pt/fmt/Makefile
index ea024d582594..82ca3c36823d 100644
--- a/drivers/iommu/generic_pt/fmt/Makefile
+++ b/drivers/iommu/generic_pt/fmt/Makefile
@@ -9,6 +9,8 @@ iommu_pt_fmt-$(CONFIG_IOMMU_PT_RISCV64) += riscv64
iommu_pt_fmt-$(CONFIG_IOMMU_PT_X86_64) += x86_64
+iommu_pt_fmt-$(CONFIG_IOMMU_PT_BCM2712) += bcm2712
+
IOMMU_PT_KUNIT_TEST :=
define create_format
obj-$(2) += iommu_$(1).o
diff --git a/drivers/iommu/generic_pt/fmt/bcm2712.h b/drivers/iommu/generic_pt/fmt/bcm2712.h
new file mode 100644
index 000000000000..e62d59181bfe
--- /dev/null
+++ b/drivers/iommu/generic_pt/fmt/bcm2712.h
@@ -0,0 +1,259 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (c) 2026 Daniel Drake
+ *
+ * BCM2712 IOMMU simple two level page table
+ */
+#ifndef __GENERIC_PT_FMT_BCM2712_H
+#define __GENERIC_PT_FMT_BCM2712_H
+
+#include "defs_bcm2712.h"
+#include "../pt_defs.h"
+
+#include <linux/bitfield.h>
+#include <linux/container_of.h>
+#include <linux/log2.h>
+#include <linux/sizes.h>
+
+enum {
+ /* Hardware provides a two-level page table */
+ PT_MAX_TOP_LEVEL = 1,
+
+ /* Hardware page size is strictly 4kb */
+ PT_GRANULE_LG2SZ = ilog2(SZ_4K),
+ PT_TABLEMEM_LG2SZ = PT_GRANULE_LG2SZ,
+
+ /* Table entries and leaf entries are 32 bits */
+ PT_ITEM_WORD_SIZE = sizeof(pt_bcm2712_entry_t),
+
+ /* Leaf entries encode a 28-bit PFN */
+ PT_MAX_OUTPUT_ADDRESS_LG2 = 28 + PT_GRANULE_LG2SZ,
+
+ /*
+ * For simplicity, only manage mappings within an address space of
+ * exactly 4GB. This is because our Level 1 directory page will be 4kb
+ * in the smallest case, permitting 1024 entries pointing at Level 0
+ * pages, each permitting 4mb of mapped memory.
+ */
+ PT_MAX_VA_ADDRESS_LG2 = ilog2(SZ_4G),
+
+ /* Level 1 base address is programmed as a 32-bit PFN */
+ PT_TOP_PHYS_MASK = GENMASK_ULL(31 + PT_GRANULE_LG2SZ, PT_GRANULE_LG2SZ),
+};
+
+/* PTE bits */
+enum {
+ BCM2712PT_VALID = BIT(28),
+ BCM2712PT_WRITE = BIT(29),
+ BCM2712PT_PAGESIZE = GENMASK(31, 30),
+ BCM2712PT_PFN = GENMASK(27, 0),
+};
+
+#define common_to_bcm2712pt(common_ptr) \
+ container_of_const(common_ptr, struct pt_bcm2712, common)
+#define to_bcm2712pt(pts) common_to_bcm2712pt((pts)->range->common)
+
+static inline pt_oaddr_t bcm2712pt_table_pa(const struct pt_state *pts)
+{
+ return oalog2_mul(FIELD_GET(BCM2712PT_PFN, pts->entry),
+ PT_GRANULE_LG2SZ);
+}
+#define pt_table_pa bcm2712pt_table_pa
+#define pt_item_oa bcm2712pt_table_pa
+
+/* All leaf entries are installed at level 0 */
+static inline bool bcm2712pt_can_have_leaf(const struct pt_state *pts)
+{
+ return pts->level == 0;
+}
+#define pt_can_have_leaf bcm2712pt_can_have_leaf
+
+/* All leaf entries are installed at level 0 */
+static inline unsigned int bcm2712pt_pgsz_lg2_to_level(struct pt_common *common,
+ unsigned int pgsize_lg2)
+{
+ return 0;
+}
+#define pt_pgsz_lg2_to_level bcm2712pt_pgsz_lg2_to_level
+
+static inline pt_vaddr_t bcm2712pt_possible_sizes(const struct pt_state *pts)
+{
+ struct pt_bcm2712 *table = common_to_bcm2712pt(pts->range->common);
+
+ if (!bcm2712pt_can_have_leaf(pts))
+ return 0;
+
+ return table->pgsize_bitmap;
+}
+#define pt_possible_sizes bcm2712pt_possible_sizes
+
+static inline unsigned int
+bcm2712pt_entry_num_contig_lg2(const struct pt_state *pts)
+{
+ struct pt_bcm2712 *table = common_to_bcm2712pt(pts->range->common);
+ u32 pgsz = FIELD_GET(BCM2712PT_PAGESIZE, pts->entry);
+
+ if (pts->level != 0 || !(pts->entry & BCM2712PT_VALID))
+ return 0;
+
+ /*
+ * Hardware only supports contiguous mapping (really just hinting) via
+ * PAGESIZE hints on each leaf entry.
+ */
+ if (pgsz == 3)
+ return ilog2(SZ_4M) - PT_GRANULE_LG2SZ;
+ else if (pgsz == 2 && table->superpage_lg2)
+ return table->superpage_lg2 - PT_GRANULE_LG2SZ;
+ else if (pgsz == 1 && table->bigpage_lg2)
+ return table->bigpage_lg2 - PT_GRANULE_LG2SZ;
+ return 0;
+}
+#define pt_entry_num_contig_lg2 bcm2712pt_entry_num_contig_lg2
+
+static inline unsigned int bcm2712pt_num_items_lg2(const struct pt_state *pts)
+{
+ return PT_TABLEMEM_LG2SZ - ilog2(PT_ITEM_WORD_SIZE);
+}
+#define pt_num_items_lg2 bcm2712pt_num_items_lg2
+
+static inline enum pt_entry_type bcm2712pt_load_entry_raw(struct pt_state *pts)
+{
+ const pt_bcm2712_entry_t *tablep =
+ pt_cur_table(pts, pt_bcm2712_entry_t);
+
+ pts->entry = READ_ONCE(tablep[pts->index]);
+ if (!(pts->entry & BCM2712PT_VALID))
+ return PT_ENTRY_EMPTY;
+ return pts->level == 0 ? PT_ENTRY_OA : PT_ENTRY_TABLE;
+}
+#define pt_load_entry_raw bcm2712pt_load_entry_raw
+
+static inline void
+bcm2712pt_install_leaf_entry(struct pt_state *pts, pt_oaddr_t oa,
+ unsigned int oasz_lg2,
+ const struct pt_write_attrs *attrs)
+{
+ pt_bcm2712_entry_t *tablep = pt_cur_table(pts, pt_bcm2712_entry_t);
+ pt_bcm2712_entry_t entry;
+
+ if (!pt_check_install_leaf_args(pts, oa, oasz_lg2))
+ return;
+
+ entry = BCM2712PT_VALID | attrs->descriptor_bits |
+ FIELD_PREP(BCM2712PT_PFN, oalog2_div(oa, PT_GRANULE_LG2SZ));
+
+ if (oasz_lg2 == PT_GRANULE_LG2SZ) {
+ WRITE_ONCE(tablep[pts->index], entry);
+ pts->entry = entry;
+ } else {
+ struct pt_bcm2712 *table =
+ common_to_bcm2712pt(pts->range->common);
+ u32 *end;
+
+ tablep += pts->index;
+ end = tablep + log2_to_int(oasz_lg2 - PT_GRANULE_LG2SZ);
+
+ /*
+ * Leaf entries can contain hints indicating multi-page
+ * contiguous mappings, presumably to permit TLB optimization
+ */
+ if (oasz_lg2 == ilog2(SZ_4M))
+ entry |= FIELD_PREP(BCM2712PT_PAGESIZE, 3);
+ else if (oasz_lg2 == table->superpage_lg2)
+ entry |= FIELD_PREP(BCM2712PT_PAGESIZE, 2);
+ else if (oasz_lg2 == table->bigpage_lg2)
+ entry |= FIELD_PREP(BCM2712PT_PAGESIZE, 1);
+
+ pts->entry = entry;
+ for (; tablep != end; tablep++, entry++)
+ WRITE_ONCE(*tablep, entry);
+ }
+}
+#define pt_install_leaf_entry bcm2712pt_install_leaf_entry
+
+static inline bool bcm2712pt_install_table(struct pt_state *pts,
+ pt_oaddr_t table_pa,
+ const struct pt_write_attrs *attrs)
+{
+ pt_bcm2712_entry_t entry =
+ BCM2712PT_VALID |
+ FIELD_PREP(BCM2712PT_PFN,
+ oalog2_div(table_pa, PT_GRANULE_LG2SZ));
+
+ return pt_table_install32(pts, entry);
+}
+#define pt_install_table bcm2712pt_install_table
+
+static inline void bcm2712pt_attr_from_entry(const struct pt_state *pts,
+ struct pt_write_attrs *attrs)
+{
+ attrs->descriptor_bits = pts->entry & BCM2712PT_WRITE;
+}
+#define pt_attr_from_entry bcm2712pt_attr_from_entry
+
+/* --- iommu */
+#include <linux/generic_pt/iommu.h>
+#include <linux/iommu.h>
+
+#define pt_iommu_table pt_iommu_bcm2712
+
+/* The common struct is in the per-format common struct */
+static inline struct pt_common *common_from_iommu(struct pt_iommu *iommu_table)
+{
+ return &container_of(iommu_table, struct pt_iommu_table, iommu)
+ ->bcm2712pt.common;
+}
+
+static inline struct pt_iommu *iommu_from_common(struct pt_common *common)
+{
+ return &container_of(common, struct pt_iommu_table, bcm2712pt.common)
+ ->iommu;
+}
+
+static inline int bcm2712_pt_iommu_set_prot(struct pt_common *common,
+ struct pt_write_attrs *attrs,
+ unsigned int iommu_prot)
+{
+ attrs->descriptor_bits = 0;
+ if (iommu_prot & IOMMU_WRITE)
+ attrs->descriptor_bits |= BCM2712PT_WRITE;
+ return 0;
+}
+#define pt_iommu_set_prot bcm2712_pt_iommu_set_prot
+
+static inline int bcm2712_pt_fmt_init(struct pt_iommu_table *fmt_table,
+ const struct pt_iommu_bcm2712_cfg *cfg)
+{
+ fmt_table->bcm2712pt.pgsize_bitmap = cfg->pgsize_bitmap;
+ fmt_table->bcm2712pt.bigpage_lg2 = cfg->bigpage_lg2;
+ fmt_table->bcm2712pt.superpage_lg2 = cfg->superpage_lg2;
+ pt_top_set_level(&fmt_table->bcm2712pt.common, PT_MAX_TOP_LEVEL);
+ return 0;
+}
+#define pt_iommu_fmt_init bcm2712_pt_fmt_init
+
+static inline void
+bcm2712pt_iommu_fmt_hw_info(struct pt_iommu_bcm2712 *table,
+ const struct pt_range *top_range,
+ struct pt_iommu_bcm2712_hw_info *info)
+{
+ info->pt_base = virt_to_phys(top_range->top_table);
+ PT_WARN_ON(info->pt_base & ~PT_TOP_PHYS_MASK);
+}
+#define pt_iommu_fmt_hw_info bcm2712pt_iommu_fmt_hw_info
+
+#if defined(GENERIC_PT_KUNIT)
+static const struct pt_iommu_bcm2712_cfg bcm2712_kunit_fmt_cfgs[] = {
+ [0] = {
+ .common.hw_max_vasz_lg2 = 32,
+ .common.hw_max_oasz_lg2 = 40,
+ .pgsize_bitmap = SZ_4K | SZ_64K | SZ_1M | SZ_4M,
+ .bigpage_lg2 = 16,
+ .superpage_lg2 = 20,
+ },
+};
+#define kunit_fmt_cfgs bcm2712_kunit_fmt_cfgs
+enum { KUNIT_FMT_FEATURES = 0 };
+#endif
+
+#endif
diff --git a/drivers/iommu/generic_pt/fmt/defs_bcm2712.h b/drivers/iommu/generic_pt/fmt/defs_bcm2712.h
new file mode 100644
index 000000000000..8d87f7ea25f5
--- /dev/null
+++ b/drivers/iommu/generic_pt/fmt/defs_bcm2712.h
@@ -0,0 +1,18 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+#ifndef __GENERIC_PT_FMT_DEFS_BCM2712_H
+#define __GENERIC_PT_FMT_DEFS_BCM2712_H
+
+#include <linux/generic_pt/common.h>
+#include <linux/types.h>
+
+typedef u32 pt_bcm2712_entry_t;
+typedef pt_bcm2712_entry_t pt_vaddr_t;
+typedef u64 pt_oaddr_t;
+
+struct bcm2712pt_write_attrs {
+ pt_bcm2712_entry_t descriptor_bits;
+ gfp_t gfp;
+};
+#define pt_write_attrs bcm2712pt_write_attrs
+
+#endif
diff --git a/drivers/iommu/generic_pt/fmt/iommu_bcm2712.c b/drivers/iommu/generic_pt/fmt/iommu_bcm2712.c
new file mode 100644
index 000000000000..059c34360785
--- /dev/null
+++ b/drivers/iommu/generic_pt/fmt/iommu_bcm2712.c
@@ -0,0 +1,10 @@
+// SPDX-License-Identifier: GPL-2.0-only
+#define PT_FMT bcm2712
+#define PT_SUPPORTED_FEATURES BIT(PT_FEAT_DMA_INCOHERENT)
+#define PT_FORCE_ENABLED_FEATURES 0
+
+/* BCM2712 has no spare software bits for tracking cache flushes */
+#define PT_SW_BIT_NOT_PRESENT
+
+#include <linux/generic_pt/iommu.h>
+#include "iommu_template.h"
diff --git a/include/linux/generic_pt/common.h b/include/linux/generic_pt/common.h
index 07ef1c8341a4..8418e7fc621e 100644
--- a/include/linux/generic_pt/common.h
+++ b/include/linux/generic_pt/common.h
@@ -204,6 +204,13 @@ struct pt_x86_64 {
struct pt_common common;
};
+struct pt_bcm2712 {
+ struct pt_common common;
+ u64 pgsize_bitmap;
+ u8 bigpage_lg2;
+ u8 superpage_lg2;
+};
+
enum {
/*
* The memory backing the tables is encrypted. Use __sme_set() to adjust
diff --git a/include/linux/generic_pt/iommu.h b/include/linux/generic_pt/iommu.h
index dd0edd02a48a..c4ee54561373 100644
--- a/include/linux/generic_pt/iommu.h
+++ b/include/linux/generic_pt/iommu.h
@@ -346,6 +346,19 @@ struct pt_iommu_x86_64_hw_info {
IOMMU_FORMAT(x86_64, x86_64_pt);
+struct pt_iommu_bcm2712_cfg {
+ struct pt_iommu_cfg common;
+ u64 pgsize_bitmap;
+ u8 bigpage_lg2;
+ u8 superpage_lg2;
+};
+
+struct pt_iommu_bcm2712_hw_info {
+ phys_addr_t pt_base;
+};
+
+IOMMU_FORMAT(bcm2712, bcm2712pt);
+
#undef IOMMU_PROTOTYPES
#undef IOMMU_FORMAT
#endif
--
2.55.0
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