Re: [Qemu-devel] Multi heterogenous CPU archs for SoC sim?

[Lluís Vilanova]

Peter Maydell writes:

>> The only realistic way to get started with such setups I see is to create a
>> new target-xxx for the specific mix, define TARGET_LONG_BITS etc.
>> appropriately in a new cpu.h, compile the needed target-xyz/*.c to unique
>> xxx-softmmu/xyz-*.o and dispatch from a cpu_init() to the two cpu_*_init().

> Yuck. Longer term if we want to support this kind of heterogeneity
> we should be removing all the compile-time assumptions and generally
> making the target-specifics suitably contained rather than leaking
> into the rest of the code.

Yup, this sounds like pointer tables. That's one of the main reasons I advocated
C++. Another reason is improving code maintainability through templates (without
impacting performance).


>> I'm guessing we may need to distinguish the TBs at runtime? Reserving
>> log2(#architectures) bits in the TBFLAGS might do, but feels ugly.
>> Probably a lot of other issues I'm not seeing yet.

> We may want the tb cache to be per-core anyway (and one thread per core),
> which would avoid the problem of trying to wedge everything into one set
> of tb_flags.

Well, AFAIU if targets have different ISAs, the same physical tb will never be
used by differing targets (ignoring the case of different targets but same ISA).



Lluis

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