[PATCH 0/7] ARM: NOMMU: MPU updates

Hi Alex,

On 28/07/17 16:51, Alexandre Torgue wrote:

Hi Vlad,

On 06/13/2017 11:05 AM, Vladimir Murzin wrote:

quoted

Hi,

This is an update of the existent MPU code which consist set of
clean-ups and enhancements. The most significant changes are in the way
how MPU settings sync-up for secondaries (PATCH 3/7) and more flexible
layout for memory (PATCH 7/7). Since there is no in-tree user of MPU,
support for M-class has been added (PATCH 6/7).

Thanks!

Changelog:

         RFC v2 -> v1
                - dropped RFC tag
           - Tested-by from Andr?s
           - rebased on 4.12-rc5

            RFC -> RFC v2
           - fixed MPU enable for v7m (PATCH 6/7)

Vladimir Murzin (7):
   ARM: NOMMU: Move out MPU setup in separate module
   ARM: NOMMU: Update MPU accessors to use cp15 helpers
   ARM: NOMMU: Rework MPU to be mostly done in C
   ARM: NOMMU: Disallow MPU for XIP
   ARM: Kconfig: Kill CONFIG_VECTORS_BASE
   ARM: V7M: Add support for MPU to M-class
   ARM: NOMMU: Use more MPU regions to cover memory

  arch/arm/Kconfig               |   9 -
  arch/arm/Kconfig-nommu         |   4 +-
  arch/arm/include/asm/cputype.h |  10 +
  arch/arm/include/asm/mpu.h     |  23 ++-
  arch/arm/include/asm/smp.h     |   2 +-
  arch/arm/include/asm/v7m.h     |  10 +
  arch/arm/kernel/asm-offsets.c  |  11 +
  arch/arm/kernel/head-nommu.S   | 128 +++++++++---
  arch/arm/kernel/smp.c          |   2 +-
  arch/arm/mm/Makefile           |   1 +
  arch/arm/mm/nommu.c            | 254 +----------------------
  arch/arm/mm/pmsa-v7.c          | 445 +++++++++++++++++++++++++++++++++++++++++
  12 files changed, 598 insertions(+), 301 deletions(-)
  create mode 100644 arch/arm/mm/pmsa-v7.c

I tested two cases on stm32h743 (based on cortes-M7):

 - NO XIP: it works fine.
 - XIP: it is ko Kernel doesn't boot.

I assume you are referring to v2...

I started investigations but no big success.
I have a question:
In arch/arm/kernel/head-nommu.S, I see that background region is set after the XIP region. It seems due to save CPU register value. But doing that you remove the XIP region just created. No ?

No. We have dedicated MPU slots for XIP and background regions, so it doesn't
matter which order they are programmed.

Other point, why (in arch/arm/kernel/head-nommu.S) we couldn't create:

1-backup region strongly-ordered
2-create SDRAM region (normal one)
3-create XIP region

By debugging I saw that issue was due to the backup region. If I remove, backup region settings done by Kernel, and I put the sequence above in my bootloader, it works fine in XIP.

It'd be handy if you can say a bit more of that issue, how far Linux was able
to boot?

Sorry to not have more precise analysis.

Thanks for giving it a try!

Vladimir

Regards
Alex