Re: [Qemu-devel] [PATCH] MIPS instruction set configuration

[Thiemo Seufer]

Dirk Behme wrote:
> Thiemo Seufer wrote:
> ...
> >I recommend to go for a sufficiently flexible interface first, and then
> >introduce it gradually in all appropriate places. A macro like:
> >
> >MIPS_OPC(ISA, ASE, CPU)
> >
> >which compares the arguments with the currently selected CPU emulation
> >and throws an RI exception if the feature doesn't exist:
> >
> >    ...
> >    case OPC_LD:
> >        MIPS_OPC(MIPS-III, 0, 0);
> >     ...
> >     break;
> >    ...
> >
> ...
> >My point is those MIPS_USES_*/MIPS_FEATURE_* should be abstracted
> >better, that is, they should move in the implementation of the
> >MIPS_OPC macro.
> 
> I really like your proposals of MIPS_OPC() and better
> abstraction of MIPS_USES_*/MIPS_FEATURE_*!
> 
> Do you think you can post a patch which introduces the basic
> parts of this functionality in the short term? Then we can
> use it as a starter for more improvements.

I'm busy this weekend.

[snip]
> >Well, there is no CPU named "R4Kc". What qemu emulates today resembles
> >mostly a 4kc, that is a MIPS32R1 CPU which has no FPU support.
> 
> Yes, I understand this. But two things:
> 
> First, in the current MIPS configuration FPU is enabled for
> "R4Kc". I think we shouldn't disable anything what is there
> at the moment, without giving an alternative for people
> using this (e.g. introducing an additional machine). And
> this only because there is no real world equivalent for this.

I agree we should have a generic "emulate everything" configuration
with MIPS64R2 + FPU + all ASEs + all non-conflicting CPU extensions.

> Second, while I agree that there is no real world equivalent
> for this, I think this is one of the biggest advantages of a
> simulator like qemu: Your are able to configure and test
> machine and feature combinations which will never exist in
> real world really quickly.

Probably, but the generic configuration will cover most of that
already.


Thiemo