Re: [PATCH] hw/mips/gt64xxx_pci: Don't endian-swap GT_PCI0_CFGADDR

[Rob Landley]

On 3/29/23 11:07, Philippe Mathieu-Daudé wrote:
> On 29/3/23 18:09, Rob Landley wrote:
>> On 3/28/23 12:02, Philippe Mathieu-Daudé wrote:
>>> On 20/3/23 17:58, Nathan Chancellor wrote:
>>>> On Wed, Mar 08, 2023 at 12:33:38AM +0100, Philippe Mathieu-Daudé wrote:
>>>>> On 23/2/23 17:19, Jiaxun Yang wrote:
>>>>>> 145e2198d749 ("hw/mips/gt64xxx_pci: Endian-swap using PCI_HOST_BRIDGE
>>>>>> MemoryRegionOps") converted CFGADDR/CFGDATA registers to use 
>>>>>> PCI_HOST_BRIDGE's
>>>>>> accessor facility and enabled byte swap for both CFGADDR/CFGDATA 
>>>>>> register.
>>>>>>
>>>>>> However CFGADDR as a ISD internal register is not controled by MByteSwap
>>>>>> bit, it follows endian of all other ISD register, which means it ties to
>>>>>> little endian.
>>>>>>
>>>>>> Move mapping of CFGADDR out of gt64120_update_pci_cfgdata_mapping to 
>>>>>> disable
>>>>>> endian-swapping.
>>>>>>
>>>>>> This should fix some recent reports about poweroff hang.
>>>>>>
>>>>>> Fixes: 145e2198d749 ("hw/mips/gt64xxx_pci: Endian-swap using 
>>>>>> PCI_HOST_BRIDGE MemoryRegionOps")
>>>>>> Signed-off-by: Jiaxun Yang <jiaxun.yang@flygoat.com>
>>>>>> ---
>>>>>>     hw/pci-host/gt64120.c | 18 ++++++------------
>>>>>>     1 file changed, 6 insertions(+), 12 deletions(-)
>>>>>
>>>>> So this works on little-endian hosts, but fails on
>>>>> big-endian ones :(
>>>>>
>>>>> I.e. on Linux we have early_console_write() -> prom_putchar()
>>>>> looping:
>>>>>
>>>>> IN: prom_putchar
>>>>> 0x8010fab8:  lbu  v0,0(v1)
>>>>> 0x8010fabc:  andi v0,v0,0x20
>>>>> 0x8010fac0:  beqz v0,0x8010fab8
>>>>> 0x8010fac4:  andi v0,a0,0xff
>>>>>
>>>>> gt64120: Illegal register read reg:0x3fc size:4 value:0x00000000
>>>>> gt64120: Illegal register read reg:0x3fc size:4 value:0x00000000
>>>>> gt64120: Illegal register read reg:0x3fc size:4 value:0x00000000
>>>>> gt64120: Illegal register read reg:0x3fc size:4 value:0x00000000
>>>>> gt64120: Illegal register read reg:0x3fc size:4 value:0x00000000
>>>>> ...
>>>>>
>>>>
>>>> Is there going to be a new version of this patch or a different solution
>>>> to the poweroff hang then? I am still seeing that with tip of tree QEMU
>>>> and I see 8.0.0-rc0 has been tagged; I would hate for this to end up in
>>>> a release version.
>>>
>>> I couldn't work a fix, however I ran our (new) tests on merge
>>> commit 3db29dcac2 which is before the offending commit 145e2198d749,
>>> and they fail. So I suppose Malta on big-endian host is badly broken
>>> since quite some time. Thus clearly nobody tests/runs Malta there.
>> 
>> I test/run malta with the mips and mipsel binaries at
>> https://landley.net/toybox/downloads/binaries/mkroot/0.8.9/ but I'm still
>> locally applying the first patch I saw to fix this (attached) until upstream
>> sorts itself out.
>> 
>> Works fine for me. Somebody said it was the wrong fix but I don't remember 
>> why...
> 
> This is a correct /partial/ fix. With this patch, Malta works on little
> endian hosts. No luck with big-endian hosts, but this was broken
> previous to 3db29dcac2 rework, so apparently not a big deal ¯\_(ツ)_/¯

No, big endian worked for me with that patch?

The build in my $PATH is QEMU emulator version 7.2.50
(v7.2.0-873-g65cc5ccf06-dirty) with that patch, and if you wget
https://landley.net/toybox/downloads/binaries/mkroot/0.8.9/mips.tgz and
./run-emulator.sh in there, the virtual net can wget http://site (the sample
image hasn't got https:// support enabled because I didn't include the build
dependency), and the virtual disk works (if you do "./run-emulator.sh -hda
blah.img" anyway, the test wrapper I mentioned creates a squashfs image for it
to mount)). Without the patch I don't even get a PCI bus. Running "file
/bin/toybox" says MSB, and the mipsel image is the little endian one anyway. I
also test s390x (which is big endian 64 bit), but I don't think this needed a
patch? (Hadn't been broken last I checked?)

I vaguely recall having tested newer qemu, but couldn't say when that was (early
february at the latest, and if so I didn't install it into /usr/bin/local. It
takes a while to build all the targets so I only really do it quarterly, usually
when I'm about to cut a toybox release and want to make sure qemu hasn't broken
anything important while I wasn't looking...)

Rob