[PATCH 0/8] arm64: improved memory map handling for /dev/mem, ACPI etc

Dave Young dyoung at redhat.com
Fri Dec 26 01:35:28 PST 2014

On 12/22/14 at 07:08pm, Ard Biesheuvel wrote:
> This series was split off from the UEFI virtmap for kexec series that I posted
> earlier today. The main purpose is to deal with the need to classify memory
> ranges as RAM or non-RAM in a consistent and comprehensive manner. This series
> applies on top of the other series.
> Patch #1 avoids an early panic if the UEFI memory map is available but UEFI
> support itself fails to initialize. In this case, there is no need to panic
> early, and we have a better chance of being able to inform the user if we deal
> with this error condition at a later time.
> Patch #2 adds iomem resource registration of UEFI memory regions. This is
> necessary because otherwise, drivers could potentially claim regions that
> are in active use by the firmware. This applies to both MMIO (NOR flash, RTC)
> and RAM ranges (runtime services code and data).
> Patch #3-6 adds support to UEFI and non-UEFI code paths to record all memory
> known to the system in the 'physmem' memblock table (if enabled). This fulfils
> a need in the /dev/mem and (upcoming) ACPI layers to be able to classify ranges
> as being backed by normal RAM even if they are not covered by the 'memory'
> memblock table, and are hence not covered by the linear direct mapping.
> The physmem code is pre-existing code that only needs minor tweaking to be made
> suitable for this purpose.
> Patch #7 enables the 'physmem' memblock table for arm64, and wires it into the
> handling of /dev/mem mappings, both to decide whether it should be mapped as
> MT_NORMAL, and whether read-write access can be allowed. (Non-RAM regions can
> be mapped read-write as long as they are not claimed by a driver in the iomem
> resource table. RAM regions can only be mapped read-only, and only if they are
> not covered by the 'memory' memblock table, and hence not covered by the linear
> mapping)
> Finally, patch #8 changes the way the virtual memory map is handled by the
> early UEFI code. Specifically, it memblock_remove()s rather than _reserves()
> UEFI reserved RAM regions, so that they are removed entirely from the linear
> mapping.
> Ard Biesheuvel (8):
>   arm64/efi: use UEFI memory map unconditionally if available
>   arm64/efi: register UEFI reserved regions as iomem resources
>   memblock: add physmem to memblock_dump_all() output
>   memblock: introduce memblock_add_phys() and memblock_is_physmem()
>   of: fdt: register physmem in early_init_dt_scan_memory()
>   arm64/efi: register physmem in reserve_regions()
>   arm64: use 'physmem' memblock to improve CONFIG_STRICT_DEVMEM handling
>   arm64/efi: memblock_remove rather than _reserve UEFI reserved RAM

Ard, It is much cleaner for this splitting.

I wonder if some of them can become general code such as register reserved
regions as iomem resources?


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