Re: [Qemu-devel] [PATCH v3 11/14] ioport: Switch dispatching to memory core layer

["Hervé Poussineau" <hpoussin@reactos.org>]

Anthony Liguori a écrit :
> On Sat, Jul 13, 2013 at 9:38 AM, Paolo Bonzini <pbonzini@redhat.com> wrote:
>> Il 11/07/2013 14:46, Andreas Färber ha scritto:
>>> sPAPR has its MemoryRegion marked Little Endian:
>>>
>>> http://git.qemu.org/?p=qemu.git;a=blobdiff;f=hw/spapr_pci.c;h=a08ed11166595bdc493065beb64d4ce5b7b0dded;hp=c2c3079d21d5be2647faf85a8c608ac995d2ca62;hb=a3cfa18eb075c7ef78358ca1956fe7b01caa1724;hpb=286d52ebfc0d0d53c2a878e454292fea14bad41b
>>>
>>> Possibly we can now apply Hervé's patches on top to remove that hack again?
>> I can post a pull request with Herve's patch, if we agree that it's the
>> right thing.
> 
> http://permalink.gmane.org/gmane.comp.emulators.qemu/221950
> 
> Here's what's happening:
> 
> 1) MMIO request goes to sPAPR PIO area, the vCPU was in BE mode but by
> the time the handler is called, the value is in host byte order.
> 
> 2) sPAPR (incorrectly) byte swaps by marking the region as little
> endian (data is now garbage)
> 
> 3) The portio layer (incorrectly) byte swaps because it is marked as
> little endian (data is now good)
> 
> 4) Dispatch happens to VGA device which (incorrectly) byte swaps
> because it is marked as little endian (data is now bad)
> 
> (2), (3), and (4) are all wrong.  By removing either (2) or (3) we can
> "fix" the regression but that's just because two wrongs make a right
> in this situation.
> 
> We should remove *all* of the LE markings from ISA devices, remove the
> portio mark, and the sPAPR mark.  That's the right fix.

OK for that if that fixes sPAPR.

Hervé