QEMU's -m option can take fractional megabyte values, and lowest granularity seems to be 0x2000. For example, run qemu with amount of memory set to 100005k (0x61A9400):
$ qemu-system-arm -machine virt -cpu cortex-a15 -m 100005k \ -bios denx/u-boot.bin -nographic
=> fdt addr $fdt_addr => fdt print /memory@40000000 memory@40000000 { reg = <0x00000000 0x40000000 0x00000000 0x061aa000>; device_type = "memory"; };
When LPAE is enabled, 1:1 mapping is created using 2 MB blocks. In case amount of memory provided to QEMU is not multiple of 2 MB, hang occurs during MMU initialization.
How to reproduce: qemu-system-arm -machine virt -m 1058 -nographic -bios u-boot.bin - boots qemu-system-arm -machine virt -m 1057 -nographic -bios u-boot.bin - hangs
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 - hang here during mmu init -
This patches rounds down to the nearest multiple of 2MB when CONFIG_ARMV7_LPAE=y.
Fixes: 3fa914af82("arm: qemu: implement enable_caches()") Signed-off-by: Igor Opaniuk igor.opaniuk@foundries.io ---
Changes in v2: - Adjust commit message, add more details
board/emulation/qemu-arm/qemu-arm.c | 12 ++++++++++++ 1 file changed, 12 insertions(+)
diff --git a/board/emulation/qemu-arm/qemu-arm.c b/board/emulation/qemu-arm/qemu-arm.c index 942f1fff571..ecfd19f1a7e 100644 --- a/board/emulation/qemu-arm/qemu-arm.c +++ b/board/emulation/qemu-arm/qemu-arm.c @@ -127,6 +127,18 @@ int dram_init(void) if (fdtdec_setup_mem_size_base() != 0) return -EINVAL;
+ /* + * When LPAE is enabled (ARMv7), + * 1:1 mapping is created using 2 MB blocks. + * + * In case amount of memory provided to QEMU + * is not multiple of 2 MB, round down the amount + * of available memory to avoid hang during MMU + * initialization. + */ + if (CONFIG_IS_ENABLED(ARMV7_LPAE)) + gd->ram_size -= (gd->ram_size % 0x200000); + return 0; }