Re: [Qemu-devel] [PATCH v3 00/22] Steps towards per CPU address-spaces

[Artyom Tarasenko]

Hi Edgar,

On Mon, Jan 13, 2014 at 8:39 AM,  <address@hidden> wrote:
> From: "Edgar E. Iglesias" <address@hidden>
>
> Hi,
>
> I'm looking at modeling systems where multiple CPUs co-exist with
> different views of their attached buses/devs.
>
> With this series I'm trying to take some steps towards having
> an address-space per CPU.

This is a very interesting approach. Would it be also possible to have
multiple address-spaces per CPU?
At least SPARC emulation would profit from that, the CPUs have
separate MMUs for data and code.

Artyom

> It's not complete but good enough for
> making it possible to model (to some extent) CPU local memories
> for MicroBlaze systems in emulation mode (TCG). I'm updating the
> petalogix-ml605 here and will follow-up later with the petalogix-s3adsp.
>
> The per-cpu address space is added into the CPUState. I tried to
> measure performance diff with having it in the CPUState->env.
> For "normal" and even for IO heavy workloads on linux kernels,
> the diff is not measurable. I also tested with a tight guest loop
> that continuously does I/O accesses and there I can see a 2.5% drop in perf.
> I dont think the runtime type check involved when casting from env to CS
> will be much of a problem.
>
> I've reordered the series and moved the AS props to the end, hoping
> we can get through the bulk of the series with less controversy and
> get it commited soon.
> I've kept the interface with properties to set AddressSpace pointers
> which I think is the more flexible approach but we can explore other
> ideas if there are.
>
> There is lots of future work needed, for example to transform more of
> the cpu_* bus accessing functions. To add more usage of AddressSpace
> properties to pass on address spaces to DMA models. Qtest mechanisms
> to target specific address spaces, etc...
>
> Cheers,
> Edgar
>
> v2 -> v3:
> Move CPU address-space prop into CPUState level.
>
> v1 -> v2:
> Add braces in cpu_memory_rw_debug.
> Avoid mixing var/code declarations in tcg_commit.
> Move per-cpu address space into CPUState.
> Reorder patch series to add the AS properties last.



-- 
Regards,
Artyom Tarasenko

linux/sparc and solaris/sparc under qemu blog:
http://tyom.blogspot.com/search/label/qemu