Messages in this thread | | | Date | Mon, 28 Jun 2021 12:54:23 +0200 | Subject | Re: [PATCH v4 1/3] iommu: io-pgtable: add DART pagetable format | From | Alexander Graf <> |
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On 27.06.21 16:34, Sven Peter wrote: > > Apple's DART iommu uses a pagetable format that shares some > similarities with the ones already implemented by io-pgtable.c. > Add a new format variant to support the required differences > so that we don't have to duplicate the pagetable handling code. > > Signed-off-by: Sven Peter <sven@svenpeter.dev> > --- > drivers/iommu/io-pgtable-arm.c | 62 ++++++++++++++++++++++++++++++++++ > drivers/iommu/io-pgtable.c | 1 + > include/linux/io-pgtable.h | 7 ++++ > 3 files changed, 70 insertions(+) > > diff --git a/drivers/iommu/io-pgtable-arm.c b/drivers/iommu/io-pgtable-arm.c > index 87def58e79b5..1dd5c45b4b5b 100644 > --- a/drivers/iommu/io-pgtable-arm.c > +++ b/drivers/iommu/io-pgtable-arm.c > @@ -127,6 +127,9 @@ > #define ARM_MALI_LPAE_MEMATTR_IMP_DEF 0x88ULL > #define ARM_MALI_LPAE_MEMATTR_WRITE_ALLOC 0x8DULL > > +#define APPLE_DART_PTE_PROT_NO_WRITE (1<<7) > +#define APPLE_DART_PTE_PROT_NO_READ (1<<8) > + > /* IOPTE accessors */ > #define iopte_deref(pte,d) __va(iopte_to_paddr(pte, d)) > > @@ -381,6 +384,15 @@ static arm_lpae_iopte arm_lpae_prot_to_pte(struct arm_lpae_io_pgtable *data, > { > arm_lpae_iopte pte; > > + 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;
What about the other bits, such as sharability, XN, etc? Do they not exist on DART? Or have they not been reverse engineered and 0s happen to "just work"?
> + } > + > if (data->iop.fmt == ARM_64_LPAE_S1 || > data->iop.fmt == ARM_32_LPAE_S1) { > pte = ARM_LPAE_PTE_nG; > @@ -1043,6 +1055,51 @@ arm_mali_lpae_alloc_pgtable(struct io_pgtable_cfg *cfg, void *cookie) > return NULL; > } > > +static struct io_pgtable * > +apple_dart_alloc_pgtable(struct io_pgtable_cfg *cfg, void *cookie) > +{ > + struct arm_lpae_io_pgtable *data; > + int i; > + > + if (cfg->oas > 36) > + return NULL; > + > + data = arm_lpae_alloc_pgtable(cfg); > + if (!data) > + return NULL; > + > + /* > + * Apple's DART always requires three levels with the first level being > + * stored in four MMIO registers. We always concatenate the first and > + * second level so that we only have to setup the MMIO registers once. > + * This results in an effective two level pagetable. > + */ > + if (data->start_level < 1) > + return NULL; > + if (data->start_level == 1 && data->pgd_bits > 2) > + return NULL; > + if (data->start_level > 1) > + data->pgd_bits = 0; > + data->start_level = 2; > + cfg->apple_dart_cfg.n_ttbrs = 1 << data->pgd_bits;
Maybe add a BUG_ON if n_ttbrs > ARRAY_SIZE(ttbr)? Or alternatively, do a normal runtime check and bail out then.
Alex
Amazon Development Center Germany GmbH Krausenstr. 38 10117 Berlin Geschaeftsfuehrung: Christian Schlaeger, Jonathan Weiss Eingetragen am Amtsgericht Charlottenburg unter HRB 149173 B Sitz: Berlin Ust-ID: DE 289 237 879
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