Re: [Qemu-devel] [PATCH for-2.0 V3] tests/acpi-test: do not run iasl on big endian machines

[Michael S. Tsirkin]

On Sun, Mar 23, 2014 at 03:17:32PM +0200, Marcel Apfelbaum wrote:
> On Sun, 2014-03-23 at 13:51 +0100, Paolo Bonzini wrote:
> > Il 23/03/2014 13:32, Marcel Apfelbaum ha scritto:
> > >> > That's the endianness of the machine we're compiling QEMU
> > >> > for, not the endianness of the machine we're compiling QEMU
> > >> > on. If for instance you're on x86_64 cross-compiling for PPC
> > >> > then HOST_WORDS_BIGENDIAN is true, but the iasl you use
> > >> > in the build process will be running on a little endian machine.
> > > Hi Peter, are you sure about this?
> > > I saw the 'target_bigendian' that does what you described above.
> > > $bigendian is the result of a little C program that checks *host's* 
> > > endian-ness.
> > > Of course I might have missed something.
> > 
> > Peter is right.  There are three systems: build (what you run on), host 
> > (what you compile for), target (always x86-64 for now for acpi-test). 
> > $bigendian and G_BYTE_ORDER check the host system.  If you wanted to 
> > test the build system's endianness, Laszlo's suggestion would be fine.
> > 
> > However, Michael is also right if we assume that iasl on bigendian can 
> > assemble, and that the problems are only on disassembling.  This is 
> > because in this particular case you'll be running an executable compiled 
> > for the host and you know that host == build.
> > 
> > I think the assumption is sane.  As far as I remember, upstream iasl 
> > doesn't compile at all on big-endian machines.  You need specific 
> > patches such as those shared by Fedora and Debian's.  Unfortunately, the 
> > patches are incomplete, they only fix assembling because that's what was 
> > needed so far to cross-compile SeaBIOS.
> 
> Hi Paolo, thanks for the help!
> I need a decision here :)
> 
> 1.
> If iasl *does* work for the scenarios used by Qemu until now,
> I can conclude that the only part that suffers from it is the
> test itself, because it dis-assembles AML code. In this case
> I can handle it in the test itself by checking the endian-ness
> (V2 already posted), or trying to dis-assemble the expected AML
> file and not failing the test if this fails.

The last option seems best to me.
It will automatically start working when iasl
disassembler is fixed and will handle any other
case of breakage, not just BE.


> 2. If iasl causes problems to run a x86_64 guest if one or both build/host
> machines are BE, we need to tweak the configuration file.
> 
> After this discussion it seems that (2.) is not the case, I think maybe 
> re-sending:
>  [PATCH for-2.0 V2] tests/acpi-test: do not run iasl on big endian machines
> 
> Is everyone OK with this?
> Thanks,
> Marcel
> 
> > Paolo
> 
>