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Re: [PATCH] hw/acpi: Set memory regions to native endian as a work aroun

From: BALATON Zoltan
Subject: Re: [PATCH] hw/acpi: Set memory regions to native endian as a work around
Date: Mon, 8 Nov 2021 16:16:35 +0100 (CET)

On Mon, 8 Nov 2021, Paolo Bonzini wrote:
On 11/8/21 15:30, Paolo Bonzini wrote:
On 11/8/21 14:05, BALATON Zoltan wrote:
When using ACPI on big endian machine (such as ppc/pegasos2 which has
a VT8231 south bridge with ACPI) writes to ACPI registers come out
byte swapped. This may be caused by a bug in memory subsystem but
until that is fixed setting the ACPI memory regions to native endian
makes it usable for big endian machines. This fixes ACPI shutdown with
pegasos2 when using the board firmware for now.
This could be reverted when the memory layer is fixed.

What is the path to the swapped writes?  Even just a backtrace might be enough to understand what's going on, and especially where the bug is.

Ok, Michael pointed me at https://lore.kernel.org/all/20211011080528-mutt-send-email-mst@kernel.org/.

I was about to say that here's the original thread:


and here's the backtrace:

#0  acpi_pm1_cnt_write (val=40, ar=0x55555695f340) at ../hw/acpi/core.c:556
#1  acpi_pm_cnt_write (opaque=0x55555695f340, addr=1, val=40, width=2) at 
#2  0x0000555555b3a82f in memory_region_write_accessor
    (mr=mr@entry=0x55555695f590, addr=1, value=value@entry=0x7fffefffdd08, 
size=size@entry=2, shift=<optimized out>, mask=mask@entry=65535, attrs=...)
    at ../softmmu/memory.c:492
#3  0x0000555555b3813e in access_with_adjusted_size
    (addr=addr@entry=1, value=value@entry=0x7fffefffdd08, size=size@entry=1, 
access_size_min=<optimized out>, access_size_max=<optimized out>, access_fn=
    0x555555b3a7b0 <memory_region_write_accessor>, mr=0x55555695f590, 
attrs=...) at ../softmmu/memory.c:554
#4  0x0000555555b3c449 in memory_region_dispatch_write (mr=mr@entry=0x55555695f590, addr=1, 
data=<optimized out>, op=<optimized out>, attrs=attrs@entry=...)
    at ../softmmu/memory.c:1511
#5  0x0000555555b2c121 in flatview_write_continue
    (fv=fv@entry=0x7fff84d23b30, addr=addr@entry=4261416709, attrs=attrs@entry=..., 
ptr=ptr@entry=0x7fffefffdec0, len=len@entry=1, addr1=<optimized out>,
     l=<optimized out>, mr=0x55555695f590) at host-utils.h:165
#6  0x0000555555b2c399 in flatview_write (len=1, buf=0x7fffefffdec0, attrs=..., 
addr=4261416709, fv=0x7fff84d23b30) at ../softmmu/physmem.c:2822
#7  subpage_write (opaque=<optimized out>, addr=<optimized out>, value=<optimized 
out>, len=1, attrs=...) at ../softmmu/physmem.c:2488
#8  0x0000555555b380de in access_with_adjusted_size
    (addr=addr@entry=3845, value=value@entry=0x7fffefffdf88, size=size@entry=1, 
access_size_min=<optimized out>, access_size_max=<optimized out>, access_fn=
    0x555555b3aa80 <memory_region_write_with_attrs_accessor>, 
mr=0x7fff84710bb0, attrs=...) at ../softmmu/memory.c:549
#9  0x0000555555b3c449 in memory_region_dispatch_write (mr=mr@entry=0x7fff84710bb0, 
addr=addr@entry=3845, data=<optimized out>, data@entry=40, op=op@entry=MO_8, 
    at ../softmmu/memory.c:1511
#10 0x0000555555c07b4c in io_writex
    (env=env@entry=0x55555666a820, iotlbentry=iotlbentry@entry=0x7fff843367f0, 
mmu_idx=1, val=val@entry=40, addr=addr@entry=4261416709,
     retaddr=retaddr@entry=140736116523268, op=MO_8) at 
#11 0x0000555555c0b5df in store_helper (op=MO_8, retaddr=<optimized out>, 
oi=<optimized out>, val=40, addr=4261416709, env=0x55555666a820) at 
#12 full_stb_mmu (env=0x55555666a820, addr=4261416709, val=40, oi=<optimized 
out>, retaddr=140736116523268) at ../accel/tcg/cputlb.c:2404
#13 0x00007fffae3b8104 in code_gen_buffer ()
#14 0x0000555555bfcfab in cpu_tb_exec (cpu=cpu@entry=0x555556661360, 
itb=itb@entry=0x7fffae3b7fc0 <code_gen_buffer+56197011>, 
    at ../accel/tcg/cpu-exec.c:357
#15 0x0000555555bfe089 in cpu_loop_exec_tb (tb_exit=0x7fffefffe668, last_tb=<synthetic 
pointer>, tb=0x7fffae3b7fc0 <code_gen_buffer+56197011>, cpu=0x555556661360)
    at ../accel/tcg/cpu-exec.c:833
#16 cpu_exec (cpu=cpu@entry=0x555556661360) at ../accel/tcg/cpu-exec.c:992
#17 0x0000555555c1bba0 in tcg_cpus_exec (cpu=cpu@entry=0x555556661360) at 
#18 0x0000555555c1c3d7 in rr_cpu_thread_fn (arg=arg@entry=0x555556661360) at 
#19 0x0000555555d5c049 in qemu_thread_start (args=0x7fffefffe750) at 
#20 0x00007ffff6a95dea in start_thread () at /lib64/libpthread.so.0
#21 0x00007ffff69c8fdf in clone () at /lib64/libc.so.6

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