Re: [Qemu-devel] [PATCH v9 00/10] 8bit AVR cores

[Michael Rolnik]

right it accesses CPU registers but from helper context.
the flow is as follows

1. there is a write to [0x0000: 0x0100) region
2. tlb_fill is called, it does the following
    a. sets env->fullwr
    b. calls cpu_loop_exit_restore.
    c. the whole block is retranslated and instead of st it generates
helper_fullwr for each store within this TB.
3. helper_fullwr calls cpu_physical_memory_write
4. sample_io_write is called and register is changed since the whole thing
is done from within a helper



On Wed, Jul 6, 2016 at 12:04 AM, Peter Maydell <address@hidden>
wrote:

> On 5 July 2016 at 21:31, Michael Rolnik <address@hidden> wrote:
> > <quote>
> >     As Richard says you have problems with trying to write
> >     CPU registers from a device anyway, but please consider
> >     trying to have some level of abstraction rather than
> >     just having the device code reach into the CPU object.
> >     The general model here is real hardware and devices, and
> >     a real device has no access into the inside workings of
> >     another one except via whatever interfaces the other
> >     device explicitly provides.
> >
> >     (Better still would be if we don't need to do any of this
> >     at all, because it gets pretty ugly pretty quickly.
> >     The guest has access to its own registers by definition,
> >     so having a second way to read and write them via memory
> >     is a bit weird.)
> > </quote>
> >
> > The code is already fixed.
>
> I just looked back at the v9 patch, and it is still
> just directly reaching into the CPU object, which is
> what I suggested you do not want to do.
>
> thanks
> -- PMM
>



-- 
Best Regards,
Michael Rolnik