[PATCH v3 0/7] arm: cache: cp15: don't map reserved region with no-map property

Patrick Delaunay patrick.delaunay at foss.st.com
Wed Apr 28 12:23:38 CEST 2021


It it the v3 serie of [1].

This v3 serie is rebased on top of v2021.07-rc1 with integrated previous series:
- [2] for stm32mp parts and added dram_bank_mmu_setup
- [3] for LMB impacts

On STM32MP15x platform we can use OP-TEE, loaded in DDR in a region
protected by a firewall. This region is reserved in device with "no-map"

Sometime the platform boot failed in U-Boot on a Cortex A7 access to
this region (depending of the binary and the issue can change with compiler
version or with code alignment), then the firewall raise an error,
for example:

E/TC:0   tzc_it_handler:19 TZC permission failure
E/TC:0   dump_fail_filter:420 Permission violation on filter 0
E/TC:0   dump_fail_filter:425 Violation @0xde5c6bf0, non-secure privileged read,
         AXI ID 5c0
E/TC:0   Panic

After investigation, the forbidden access is a speculative request performed
by the Cortex A7 because all the DDR is mapped as MEMORY with CACHEABLE

The issue is solved only when the region reserved by OP-TEE is no more
mapped in U-Boot as it is already done in Linux kernel.

Tested on DK2 board with OP-TEE 3.12 / TF-A 2.4:

With hard-coded address for OP-TEE reserved memory,
the error doesn't occur.

 void dram_bank_mmu_setup(int bank)

    	for (i = start >> MMU_SECTION_SHIFT;
 	     i < (start >> MMU_SECTION_SHIFT) + (size >> MMU_SECTION_SHIFT);
 	     i++) {
 		if (i >= 0xde0)
 			option = INVALID_ENTRY;
 		set_section_dcache(i, option);

Just by modifying the test on 0xde0 to 0xdf0, the OP-TEE memory protected
by firewall is mapped cacheable and the error occurs.

I think that can be a general issue for ARM architecture: the no-map tag
in device should be respected by U-Boot.

But I don't propose a generic
solution in arm/lib/cache-cp15.c:dram_bank_mmu_setup()
because the device tree parsing done in lmb_init_and_reserve() take a
long time when it is executed without data cache.

=> the previous path 7/7 of v2 series is dropped to avoid
   performance issue on other ARM target.

To avoid this issue on stm32mp32mp platform, this V3 series moves
the lmb initialization in enable_caches() and the lmb variable becomes a
static struct.

This v3 series is composed by 7 patches
- 1..3/7: preliminary steps to support flags in library in lmb
  (as it is done in memblock.c in Linux)
- 4/7: unitary test on the added feature in lmb lib
- 5/7: save the no-map flags in lmb when the device tree is parsed
- 6/7: solve issue for the size of cacheable area in pre-reloc case
- 7/7: update the stm32mp mmu support

See also [4] which handle same speculative access on armv8 for area
with Executable attribute.

[1] http://patchwork.ozlabs.org/project/uboot/list/?series=228543&state=*
[2] http://patchwork.ozlabs.org/project/uboot/list/?series=228202&state=*
[3] http://patchwork.ozlabs.org/project/uboot/list/?series=227570&state=*
[4] http://patchwork.ozlabs.org/project/uboot/patch/20200903000106.5016-1-marek.bykowski@gmail.com/


Changes in v3:
- NEW: solve performance issue as relocated DT is not marked cacheable
- call lmb_init_and_reserve when data cache is activated in enable_caches()
- drop v2 patch "arm: cache: cp15: don't map the reserved region
  with no-map property"

Changes in v2:
- remove unnecessary comments in lmb.h
- rebase on latest lmb patches
- NEW: update in stm32mp specific MMU setup functions

Patrick Delaunay (7):
  lmb: Add support of flags for no-map properties
  lmb: add lmb_is_reserved_flags
  lmb: add lmb_dump_region() function
  test: lmb: add test for lmb_reserve_flags
  image-fdt: save no-map parameter of reserve-memory
  stm32mp: Increase the reserved memory in board_get_usable_ram_top
  stm32mp: don't map the reserved region with no-map property

 arch/arm/mach-stm32mp/cpu.c       | 17 +++++-
 arch/arm/mach-stm32mp/dram_init.c |  3 +-
 common/image-fdt.c                | 23 +++++---
 include/lmb.h                     | 21 +++++++
 lib/lmb.c                         | 94 ++++++++++++++++++++++---------
 test/lib/lmb.c                    | 89 +++++++++++++++++++++++++++++
 6 files changed, 209 insertions(+), 38 deletions(-)


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