Re: [PATCH 1/3] iommu: io-pgtable: add DART pagetable format
From: Robin Murphy
Date: Wed Mar 24 2021 - 12:38:58 EST
On 2021-03-20 15:19, Sven Peter wrote:
Apple's DART iommu uses a pagetable format that's very similar to the ones
already implemented by io-pgtable.c.
Add a new format variant to support the required differences.
TBH there look to be more differences than similarities, but I guess we
already opened that door with the Mali format, and nobody likes writing
pagetable code :)
Signed-off-by: Sven Peter <sven@xxxxxxxxxxxxx>
---
drivers/iommu/Kconfig | 13 +++++++
drivers/iommu/io-pgtable-arm.c | 70 ++++++++++++++++++++++++++++++++++
drivers/iommu/io-pgtable.c | 3 ++
include/linux/io-pgtable.h | 6 +++
4 files changed, 92 insertions(+)
diff --git a/drivers/iommu/Kconfig b/drivers/iommu/Kconfig
index 192ef8f61310..3c95c8524abe 100644
--- a/drivers/iommu/Kconfig
+++ b/drivers/iommu/Kconfig
@@ -39,6 +39,19 @@ config IOMMU_IO_PGTABLE_LPAE
sizes at both stage-1 and stage-2, as well as address spaces
up to 48-bits in size.
+config IOMMU_IO_PGTABLE_APPLE_DART
Does this really need to be configurable? I don't think there's an
appreciable code saving to be had, and it's not like we do it for any of
the other sub-formats.
+ bool "Apple DART Descriptor Format"
+ select IOMMU_IO_PGTABLE
+ select IOMMU_IO_PGTABLE_LPAE
+ depends on ARM64 || (COMPILE_TEST && !GENERIC_ATOMIC64)
+ help
+ Enable support for the Apple DART iommu pagetable format.
+ This format is a variant of the ARMv7/v8 Long Descriptor
+ Format specific to Apple's iommu found in their SoCs.
+
+ Say Y here if you have a Apple SoC like the M1 which
+ contains DART iommus.
+
config IOMMU_IO_PGTABLE_LPAE_SELFTEST
bool "LPAE selftests"
depends on IOMMU_IO_PGTABLE_LPAE
diff --git a/drivers/iommu/io-pgtable-arm.c b/drivers/iommu/io-pgtable-arm.c
index 87def58e79b5..18674469313d 100644
--- a/drivers/iommu/io-pgtable-arm.c
+++ b/drivers/iommu/io-pgtable-arm.c
@@ -127,6 +127,10 @@
#define ARM_MALI_LPAE_MEMATTR_IMP_DEF 0x88ULL
#define ARM_MALI_LPAE_MEMATTR_WRITE_ALLOC 0x8DULL
+/* APPLE_DART_PTE_PROT_NO_WRITE actually maps to ARM_LPAE_PTE_AP_RDONLY */
+#define APPLE_DART_PTE_PROT_NO_WRITE (1<<7)
Given that there's apparently zero similarity with any of the other
attributes/permissions, this seems more like a coincidence that probably
doesn't need to be called out.
+#define APPLE_DART_PTE_PROT_NO_READ (1<<8)
+
Do you have XN permission? How about memory type attributes?
/* IOPTE accessors */
#define iopte_deref(pte,d) __va(iopte_to_paddr(pte, d))
@@ -381,6 +385,17 @@ static arm_lpae_iopte arm_lpae_prot_to_pte(struct arm_lpae_io_pgtable *data,
{
arm_lpae_iopte pte;
+#ifdef CONFIG_IOMMU_IO_PGTABLE_APPLE_DART
As a general tip, prefer IS_ENABLED() to inline #ifdefs.
+ if (data->iop.fmt == ARM_APPLE_DART) { > + pte = 0;
+ if (!(prot & IOMMU_WRITE))
+ pte |= APPLE_DART_PTE_PROT_NO_WRITE;
+ if (!(prot & IOMMU_READ))
+ pte |= APPLE_DART_PTE_PROT_NO_READ;
+ return pte;
+ }
+#endif
+
if (data->iop.fmt == ARM_64_LPAE_S1 ||
data->iop.fmt == ARM_32_LPAE_S1) {
pte = ARM_LPAE_PTE_nG;
@@ -1043,6 +1058,54 @@ arm_mali_lpae_alloc_pgtable(struct io_pgtable_cfg *cfg, void *cookie)
return NULL;
}
+#ifdef CONFIG_IOMMU_IO_PGTABLE_APPLE_DART
Similarly, prefer __maybe_unused rather than #ifdefing functions if they
don't contain any config-dependent references.
+static struct io_pgtable *
+apple_dart_alloc_pgtable(struct io_pgtable_cfg *cfg, void *cookie)
+{
+ struct arm_lpae_io_pgtable *data;
+
+ if (cfg->ias > 38)
+ return NULL;
+ if (cfg->oas > 36)
+ return NULL;
+
+ if (!cfg->coherent_walk)
+ return NULL;
For completeness you should probably also reject any quirks, since none
of them are applicable either.
+
+ cfg->pgsize_bitmap &= SZ_16K;
No block mappings?
+ if (!cfg->pgsize_bitmap)
+ return NULL;
+
+ data = arm_lpae_alloc_pgtable(cfg);
+ if (!data)
+ return NULL;
+
+ /*
+ * the hardware only supports this specific three level pagetable layout with
+ * the first level being encoded into four hardware registers
+ */
+ data->start_level = ARM_LPAE_MAX_LEVELS - 2;
The comment implies that walks should start at level 1 (for a 3-level
table), but the code here says (in an unnecessarily roundabout manner)
level 2 :/
Which is it?
+ data->pgd_bits = 13;
What if ias < 38? Couldn't we get away with only allocating as much as
we actually need?
+ data->bits_per_level = 11;
+
+ data->pgd = __arm_lpae_alloc_pages(ARM_LPAE_PGD_SIZE(data), GFP_KERNEL,
+ cfg);
+ if (!data->pgd)
+ goto out_free_data;
+
+ cfg->apple_dart_cfg.pgd[0] = virt_to_phys(data->pgd);
+ cfg->apple_dart_cfg.pgd[1] = virt_to_phys(data->pgd + 0x4000);
+ cfg->apple_dart_cfg.pgd[2] = virt_to_phys(data->pgd + 0x8000);
+ cfg->apple_dart_cfg.pgd[3] = virt_to_phys(data->pgd + 0xc000);
+
+ return &data->iop;
+
+out_free_data:
+ kfree(data);
+ return NULL;
+}
+#endif
+
struct io_pgtable_init_fns io_pgtable_arm_64_lpae_s1_init_fns = {
.alloc = arm_64_lpae_alloc_pgtable_s1,
.free = arm_lpae_free_pgtable,
@@ -1068,6 +1131,13 @@ struct io_pgtable_init_fns io_pgtable_arm_mali_lpae_init_fns = {
.free = arm_lpae_free_pgtable,
};
+#ifdef CONFIG_IOMMU_IO_PGTABLE_APPLE_DART
+struct io_pgtable_init_fns io_pgtable_apple_dart_init_fns = {
+ .alloc = apple_dart_alloc_pgtable,
+ .free = arm_lpae_free_pgtable,
+};
+#endif
+
#ifdef CONFIG_IOMMU_IO_PGTABLE_LPAE_SELFTEST
static struct io_pgtable_cfg *cfg_cookie __initdata;
diff --git a/drivers/iommu/io-pgtable.c b/drivers/iommu/io-pgtable.c
index 6e9917ce980f..d86590b0673a 100644
--- a/drivers/iommu/io-pgtable.c
+++ b/drivers/iommu/io-pgtable.c
@@ -27,6 +27,9 @@ io_pgtable_init_table[IO_PGTABLE_NUM_FMTS] = {
#ifdef CONFIG_AMD_IOMMU
[AMD_IOMMU_V1] = &io_pgtable_amd_iommu_v1_init_fns,
#endif
+#ifdef CONFIG_IOMMU_IO_PGTABLE_APPLE_DART
+ [ARM_APPLE_DART] = &io_pgtable_apple_dart_init_fns,
+#endif
};
struct io_pgtable_ops *alloc_io_pgtable_ops(enum io_pgtable_fmt fmt,
diff --git a/include/linux/io-pgtable.h b/include/linux/io-pgtable.h
index a4c9ca2c31f1..19d9b631d319 100644
--- a/include/linux/io-pgtable.h
+++ b/include/linux/io-pgtable.h
@@ -16,6 +16,7 @@ enum io_pgtable_fmt {
ARM_V7S,
ARM_MALI_LPAE,
AMD_IOMMU_V1,
+ ARM_APPLE_DART,
IO_PGTABLE_NUM_FMTS,
};
@@ -136,6 +137,10 @@ struct io_pgtable_cfg {
u64 transtab;
u64 memattr;
} arm_mali_lpae_cfg;
+
+ struct {
+ u64 pgd[4];
Nit: in the driver you call the registers "TTBR" rather than "PGD". The
config here tries to represent hardware/architecture definitions rather
than internal abstractions.
Robin.
+ } apple_dart_cfg;
};
};
@@ -250,5 +255,6 @@ extern struct io_pgtable_init_fns io_pgtable_arm_64_lpae_s2_init_fns;
extern struct io_pgtable_init_fns io_pgtable_arm_v7s_init_fns;
extern struct io_pgtable_init_fns io_pgtable_arm_mali_lpae_init_fns;
extern struct io_pgtable_init_fns io_pgtable_amd_iommu_v1_init_fns;
+extern struct io_pgtable_init_fns io_pgtable_apple_dart_init_fns;
#endif /* __IO_PGTABLE_H */
--
2.25.1