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ACPI endianness

From: BALATON Zoltan
Subject: ACPI endianness
Date: Sun, 10 Oct 2021 15:24:32 +0200 (CEST)


I'm trying to fix shutdown and reboot on pegasos2 which uses ACPI as part of the VIA VT8231 (similar to and modelled in hw/isa/vt82c686b.c) and found that the guest writes to ACPI PM1aCNT register come out with wrong endianness but not shure why. I have this:

$ qemu-system-ppc -M pegasos2 -monitor stdio
(qemu) info mtree
memory-region: pci1-io
  0000000000000000-000000000000ffff (prio 0, i/o): pci1-io
    0000000000000f00-0000000000000f7f (prio 0, i/o): via-pm
      0000000000000f00-0000000000000f03 (prio 0, i/o): acpi-evt
      0000000000000f04-0000000000000f05 (prio 0, i/o): acpi-cnt
      0000000000000f08-0000000000000f0b (prio 0, i/o): acpi-tmr

memory-region: system
  0000000000000000-ffffffffffffffff (prio 0, i/o): system
    0000000000000000-000000001fffffff (prio 0, ram): pegasos2.ram
    0000000080000000-00000000bfffffff (prio 0, i/o): alias pci1-mem0-win 
@pci1-mem 0000000080000000-00000000bfffffff
    00000000c0000000-00000000dfffffff (prio 0, i/o): alias pci0-mem0-win 
@pci0-mem 00000000c0000000-00000000dfffffff
    00000000f1000000-00000000f100ffff (prio 0, i/o): mv64361
    00000000f8000000-00000000f8ffffff (prio 0, i/o): alias pci0-io-win @pci0-io 
    00000000f9000000-00000000f9ffffff (prio 0, i/o): alias pci0-mem1-win 
@pci0-mem 0000000000000000-0000000000ffffff
    00000000fd000000-00000000fdffffff (prio 0, i/o): alias pci1-mem1-win 
@pci1-mem 0000000000000000-0000000000ffffff
    00000000fe000000-00000000feffffff (prio 0, i/o): alias pci1-io-win @pci1-io 
    00000000ff800000-00000000ffffffff (prio 0, i/o): alias pci1-mem3-win 
@pci1-mem 00000000ff800000-00000000ffffffff
    00000000fff00000-00000000fff7ffff (prio 0, rom): pegasos2.rom

The guest (which is big endian PPC and I think wotks on real hardware) writes to 0xf05 in the io region which should be the high byte of the little endian register but in the acpi code it comes out wrong, instead of 0x2800 I get in acpi_pm1_cnt_write: val=0x28

The memory regions involved are:

acpi-cnt (hw/acpi/core.c):

static const MemoryRegionOps acpi_pm_cnt_ops = {
    .read = acpi_pm_cnt_read,
    .write = acpi_pm_cnt_write,
    .impl.min_access_size = 2,
    .valid.min_access_size = 1,
    .valid.max_access_size = 2,
    .endianness = DEVICE_LITTLE_ENDIAN,

via-pm (hw/isa/vt82c686.c):

static const MemoryRegionOps pm_io_ops = {
    .read = pm_io_read,
    .write = pm_io_write,
    .endianness = DEVICE_NATIVE_ENDIAN,
    .impl = {
        .min_access_size = 1,
        .max_access_size = 1,

Also tried removing .impl from pm_io_ops but that does not help. Changing acpi_pm_cnt_ops to DEVICE_NATIVE_ENDIAN fixes it but not sure what else could that break. Should these ACPI regions be native endian or how else to fix this for the vt82xx case?


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