On 5/25/24 13:50, Bernhard Beschow wrote:
Am 25. Mai 2024 13:41:54 UTC schrieb Bernhard Beschow <shen...@gmail.com>:
Am 5. März 2024 13:52:34 UTC schrieb Peter Maydell <peter.mayd...@linaro.org>:
From: Richard Henderson <richard.hender...@linaro.org>
If translation is disabled, the default memory type is Device, which
requires alignment checking. This is more optimally done early via
the MemOp given to the TCG memory operation.
Reviewed-by: Philippe Mathieu-Daudé <phi...@linaro.org>
Reported-by: Idan Horowitz <idan.horow...@gmail.com>
Signed-off-by: Richard Henderson <richard.hender...@linaro.org>
Message-id: 20240301204110.656742-6-richard.hender...@linaro.org
Resolves: https://gitlab.com/qemu-project/qemu/-/issues/1204
Signed-off-by: Richard Henderson <richard.hender...@linaro.org>
Signed-off-by: Peter Maydell <peter.mayd...@linaro.org>
Hi,
This change causes an old 4.14.40 Linux kernel to panic on boot using the
sabrelite machine:
[snip]
Alignment trap: init (1) PC=0x76f1e3d4 Instr=0x14913004 Address=0x76f34f3e FSR
0x001
Alignment trap: init (1) PC=0x76f1e3d8 Instr=0x148c3004 Address=0x7e8492bd FSR
0x801
Alignment trap: init (1) PC=0x76f0dab0 Instr=0x6823 Address=0x7e849fbb FSR 0x001
Alignment trap: init (1) PC=0x76f0dab2 Instr=0x6864 Address=0x7e849fbf FSR 0x001
scsi 0:0:0:0: Direct-Access QEMU QEMU HARDDISK 2.5+ PQ: 0 ANSI: 5
fsl-asoc-card sound: ASoC: CODEC DAI sgtl5000 not registered
imx-sgtl5000 sound: ASoC: CODEC DAI sgtl5000 not registered
imx-sgtl5000 sound: snd_soc_register_card failed (-517)
Alignment trap: init (1) PC=0x76eac95a Instr=0xf8dd5015 Address=0x7e849b05 FSR
0x001
Alignment trap: not handling instruction f8dd5015 at [<76eac95a>]
Unhandled fault: alignment exception (0x001) at 0x7e849b05
pgd = 9c59c000
[7e849b05] *pgd=2c552831, *pte=109eb34f, *ppte=109eb83f
Kernel panic - not syncing: Attempted to kill init! exitcode=0x00000007
---[ end Kernel panic - not syncing: Attempted to kill init! exitcode=0x00000007
As you can see, some alignment exceptions are handled by the kernel, the last one
isn't. I added some additional printk()'s and traced it down to this location in the
kernel:
<https://github.com/torvalds/linux/blob/v4.14/arch/arm/mm/alignment.c#L762>
which claims that ARMv6++ CPUs can handle up to word-sized unaligned accesses, thus
no fixup is needed.
I hope that this will be sufficient for a fix. Let me know if you need any
additional information.
I'm performing a direct kernel boot. On real hardware, a bootloader is involved
which probably enables unaligned access. This may explain why it works there
but not in QEMU any longer.
To fix direct kernel boot, it seems as if the "built-in bootloader" would need
to be adapted/extended [1]. Any ideas?
I strongly suspect a kernel bug. Either mmu disabled or attempting unaligned access on
pages mapped as Device instead of Normal.
r~
