Re: [Qemu-devel] mipsIV support for mips-linux-user

[Vince Weaver <vince@csl.cornell.edu>]

>> Because of this the generated assembly in the debug output
>> unconditionally generates an illegal instruction exception the first time
>> a cop1x instruction is executed (in my case, "msub.d")
>
> This instruction is clearly marked as MIPS64 only in the manual.

I'm running MIPSIV compiled o32 binaries.  Even though the binaries
are 32-bits, they are running on a 64-bit enabled OS.  (I have actual r12k 
and r5k machines running Debian Linux.  They have 64-bit kernels but 
32-bit userspace).

mips-linux-user can run these executables fine if you hack it so that
cop1x instructions are enabled.

Perhaps the proper solution is to run the binaries under 
mips64-linux-user, but there you run into the 64-bit qemu-linux-user
can't load 32-bit ELF files problem.  I'm also not sure if 
mips64-linux-user implements the o32 syscalls.

> I think this should be enabled in cpu_reset(), where env->hflags is
> setup for user mode.

That's currently what I am doing to enable these binaries to run.

> But I am actually concern about the results you get when enabling
> MIPS_HFLAG_COP1X. If your program is expecting to have the FPU in 64-bit
> mode you may have really strange results. Did you check them?

I'm running the Spec2k benchmarks and the results are as close as can be 
expected to the actual hardware.

Vince