Re: [Qemu-devel] [PATCH][RFC] Split non-TCG bits out of exec.c

[Anthony Liguori]

Fabrice Bellard wrote:
> I suggest to go even further: there should be a way in QEMU to define
> CPUs which do not rely on the dynamic translator and this choice should
> be doable at runtime (i.e. not with a bunch of #ifdefs as you may do
> it). This way you could not only plug KVM CPUs without having the
> equivalent TCG one, but also CPUs from other sources (i.e. the x86
> interpreter of malc, or the cycle accurate PTLsim x86 emulator).
>   

Today, we do this with KVM support without any ifdefs (what's in SVN 
right now).  We leave the TCG and the KVM state in CPUState, and then 
just use the appropriate cpu_exec() loop to run depending on the CPU type.

We could go a step further and split out the core x86 CPU state from 
CPUX86State, and then introduce a CPUTCGState and CPUKVMState that both 
include CPUX86State but that seems like a lot of churn for little gain 
(KVM just adds two more fields to CPUX86State).

What I'm trying to do with this patch, is make it possible to get rid of 
the TCG code altogether for targets that only support KVM and not TCG 
(ia64, s390, etc).

How I'll eventually get rid of it is not with #ifdefs, but by just not 
compiling in all the TCG code, cpu-exec.c, exec.c and instead just 
compiling in a kvm-exec.c or something like that.

Regards,

Anthony Liguori

> Fabrice.
>
>