On Fri, 5 Feb 2021 at 18:38, Igor Opaniuk igor.opaniuk@foundries.io wrote:
Hi,
With this commit 3fa914af82("arm: qemu: implement enable_caches()") introduced, which enables instruction/data caches for qemu-arm target, U-Boot sometimes hangs during MMU init procedure :
DRAM: 1 GiB initcall: 60011df8 initcall: 60011904 New Stack Pointer is: 80fffe90 initcall: 60011a20 initcall: 60011bcc initcall: 60011bd4 initcall: 600119b4 Relocation Offset is: 22042000 Relocating to 82042000, new gd at 81001ed0, sp at 80fffe90 initcall: 60011b8c initcall: 82053ea0 initcall: 82053ea8 initcall: 60012040 (relocated to 82054040) dram_bank_mmu_setup: bank: 0
This issue reproduces every time when the amount of memory provided to QEMU is not 2MB granular. Looks like it might be some unexpected alignment issue.
Test results (QEMU v5.2.0 release): qemu-system-arm -machine virt -m 1058 -nographic -bios u-boot.bin - boots OK qemu-system-arm -machine virt -m 1057 -nographic -bios u-boot.bin - hangs qemu-system-arm -machine virt -m 1056 -nographic -bios u-boot.bin - boots OK qemu-system-arm -machine virt -m 1055 -nographic -bios u-boot.bin - hangs
Unfortunately I didn't have a chance to investigate this further, so just sharing my current observations. Thanks for any input.
Hello Igor,
enable_caches() results in a 1:1 mapping to be created, and since LPAE has been enabled as well, the 1:1 mapping is created using 2 MB blocks. So I am not surprised that using a value that is not a multiple of 2 MB causes problems.
I'd suggest implementing a simple fix, e.g., just round down the amount of available memory, as this is not something that is likely to ever be a problem on real systems.