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mmu: add virtual memory Kconfigs

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Specify the virtual address range for kernel mappings.

Signed-off-by: Andrew Boie <andrew.p.boie@intel.com>
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Andrew Boie 2020-07-08 21:34:02 -07:00 committed by Anas Nashif
parent 88ddce652c
commit 2c3523e421
1 changed files with 39 additions and 0 deletions
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39
arch/Kconfig
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@ -519,6 +519,45 @@ config SRAM_REGION_PERMISSIONS
If not enabled, all SRAM mappings will allow supervisor mode to
read, write, and execute. User mode support requires this.
config KERNEL_VM_BASE
hex "Base virtual address for the kernel"
depends on MMU
default 0xFFFF800000000000 if 64BIT
default 0xC0000000
help
Define the base virtual memory address for the core kernel. There will
be a permemant mapping of all RAM starting at this virtual address,
with any unused space up to the KERNEL_VM_LIMIT available for memory
mappings. This denotes the start of the RAM mapping and may not be
the base address of the kernel itself, but the offset of the kernel here
will be the same as the offset from the beginning of physical memory
where it was loaded.
The value here must have similar alignment to the base physical address,
such that the same page tables can be mapped to the top-level paging
structure entries for the virtual and physical address.
It is valid to set this to SRAM_BASE_ADDRESS, in which case RAM will
be identity-mapped. Otherwise, the SRAM and KERNEL_VM regions must
not overlap.
The default for 64-bit presumes a 48-bit canonical address space.
config KERNEL_VM_LIMIT
hex "Upper bound on kernel address space"
depends on MMU
default 0xFFFFFFFFFFFFFFFF if 64BIT
default 0xFFFFFFFF
help
Inclusive upper bound on the virtual memory area reserved for the kernel.
No mappings will be made past this point. Constraining this helps control
how much memory is used for page tables.
The area defined by KERNEL_VM_BASE to KERNEL_VM_LIMIT must have enough
room to map system RAM, plus any driver mappings. Further mappings
may be made at runtime depending on configuration options (such as
memory-mapping stacks, VDSO pages, etc).
config MEMORY_PROTECTION
bool
help