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

["Michael S. Tsirkin" <mst@redhat.com>]

On Mon, Feb 20, 2023 at 07:24:59PM +0100, BALATON Zoltan wrote:
> On Tue, 22 Feb 2022, Michael S. Tsirkin wrote:
> > On Wed, Jan 19, 2022 at 04:19:14AM -0500, Michael S. Tsirkin wrote:
> > > On Sat, Nov 13, 2021 at 07:47:20PM +0100, BALATON Zoltan wrote:
> > > > On Mon, 8 Nov 2021, BALATON Zoltan wrote:
> > > > > 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/.
> > > > 
> > > > Ping? I haven't seen an alternative fix yet. If you don't have time now this
> > > > could be postponed to next version with the native endian work around for
> > > > now.
> > > > 
> > > > Regards,
> > > > BALATON Zoltan
> > > 
> > > Paolo, ping?
> > 
> > ping
> 
> Can this be fixed please or my proposed workaround taken until it will be?
> Original patch I've sent is here:
> http://patchew.org/QEMU/20211108130934.59B48748F52@zero.eik.bme.hu/
> 
> I hope to make pegasos2 more usable in next release so maybe more people
> will want to use it soon.
> 
> Regards,
> BALATON Zoltan

Any chance of fixing it in memory core? No one else seems to care.


I think fundamentally you need to check for the condition
Size < mr->ops->impl.min_access_size in memory_region_dispatch_write
and then make a read, combine the result with
the value and make a write.






> > > > > I was about to say that here's the original thread:
> > > > > 
> > > > > https://lists.nongnu.org/archive/html/qemu-devel/2021-10/msg01972.html
> > > > > 
> > > > > 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 ../hw/acpi/core.c:602
> > > > > #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, attrs=...)
> > > > >    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
> > > > > ../accel/tcg/cputlb.c:1420
> > > > > #11 0x0000555555c0b5df in store_helper (op=MO_8, retaddr=<optimized
> > > > > out>, oi=<optimized out>, val=40, addr=4261416709, env=0x55555666a820)
> > > > > at ../accel/tcg/cputlb.c:2355
> > > > > #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>,
> > > > > tb_exit=tb_exit@entry=0x7fffefffe668)
> > > > >    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 ../accel/tcg/tcg-accel-ops.c:67
> > > > > #18 0x0000555555c1c3d7 in rr_cpu_thread_fn
> > > > > (arg=arg@entry=0x555556661360) at ../accel/tcg/tcg-accel-ops-rr.c:214
> > > > > #19 0x0000555555d5c049 in qemu_thread_start (args=0x7fffefffe750) at
> > > > > ../util/qemu-thread-posix.c:556
> > > > > #20 0x00007ffff6a95dea in start_thread () at /lib64/libpthread.so.0
> > > > > #21 0x00007ffff69c8fdf in clone () at /lib64/libc.so.6
> > > > > 
> > > 
> > 
> >