arm: cache: cp15: don't map reserved region with no-map property
Hi,
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" property.
But 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 a 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 property.
The issue is solved only when the region reserved by OP-TEE is no more mapped in U-Boot (mapped as DEVICE/NON-CACHEABLE wasn't enough) as it is already done in Linux kernel.
I think that can be a general issue for ARM architecture: the no-map tag in device should be respected by U-boot, so I propose a generic solution in arm/lib/cache-cp15.c:dram_bank_mmu_setup().
This RFC serie is composed by 7 patches - 1..4/7: preliminary steps to support flags in library in lmb (as it is done in memblock.c in Linux) - 5/7: unitary test on the added feature in lmb lib - 6/7: save the no-map flags in lmb when the device tree is parsed - 7/7: update the generic behavior for "no-map" region in arm/lib/cache-cp15.c::dram_bank_mmu_setup()
I can change this last patch if it is required by other ARM architecture; it is a weak function so I can avoid to map the region with "no-map" property in device tree only for STM32MP architecture (in arch/arm/mach-stm32mp/cpu.c).
See also [1] which handle same speculative access on armv8 for area with Executable attribute.
[1] http://patchwork.ozlabs.org/project/uboot/patch/20200903000106.5016-1-marek....
Regards Patrick
Patrick Delaunay (7): lmb: Add support of flags for no-map properties lmb: add lmb_is_reserved_flags lmb: remove lmb_region.size lmb: add lmb_dump_region() function test: lmb: add test for lmb_reserve_flags image-fdt: save no-map parameter of reserve-memory arm: cache: cp15: don't map the reserved region with no-map property
arch/arm/include/asm/system.h | 3 + arch/arm/lib/cache-cp15.c | 17 +++++- common/image-fdt.c | 23 +++++--- include/lmb.h | 22 +++++++- lib/lmb.c | 100 +++++++++++++++++++++++----------- test/lib/lmb.c | 89 ++++++++++++++++++++++++++++++ 6 files changed, 210 insertions(+), 44 deletions(-)