On 12/30/14 at 01:21pm, Ard Biesheuvel wrote:

On 30 December 2014 at 09:25, Dave Young [off-list ref] wrote:

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On 12/29/14 at 09:22am, Ard Biesheuvel wrote:

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On 26 December 2014 at 09:35, Dave Young [off-list ref] wrote:

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On 12/22/14 at 07:08pm, Ard Biesheuvel wrote:

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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.

Thanks for having a look.

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

AFAICT, the x86 code adds reservations for such regions to the E820
memory map, which in turn is used to memblock_reserve() the actual
memory. Also, sharing of the RTC is handled with a dedicated mutex in
the runtime services wrapper code (and x86 does not even use the time
related runtime services as they are broken on many firmware
implementations) so blindly applying the same logic to x86 or ia64
would likely break stuff.

Ok, I think bootloader will pass the E820 ranges though it can not tell
which region is for what.

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Do you (or Mark) have any feedback on the utility of this series in
the ACPI context? I failed to mention in the cover letter that
memblock_is_physmem() now serves the purpose of page_is_ram(), i.e.,
whether a physical region is backed by a slice of RAM that was left
out of the kernel's linear mapping.

I will do some test later along with the stable mapping stuff.

The whole patchset works well without the last patch.

I found that patch 8/8 caused system boot hangs very early.
Just after stub print something about virtmap..

Any idea about it? I tested your patches upon 3.18.

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Cheers.

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BTW, with previous stable mapping patches on modified 3.18 tree kexec kernel
panics because of damaged efi mempry map arrays. It contains some
random value instead of right addresses so that virt_to_phys return
same value for vendor field. Will do more debugging maybe I missed something.
Any clue for debugging above issue will be appreciated.

No clues, unfortunately. The memory map is not used after early boot,
so it may be getting clobbered at any point between the first boot and
the second boot.

It was caused by uefi sys table/mmap start addresses changes.
I generate dtb from acpi=off boot /proc/device-tree, and use the dtb for kexec
boot, but seems mmap addresses changes sometimes.

Do you know have plan or status in Linaro for exporting dtb for acpi booting?

Thanks
Dave