Re: [Qemu-devel] [RFC 0/5] execute code from mmio area

[Frederic Konrad]

On 02/04/2017 02:17 PM, Peter Maydell wrote:
> On 4 February 2017 at 12:52, Frederic Konrad <address@hidden> wrote:
>> Is that the case that we might get a Bad RAM address error or some such
>> if we are not on a page boundary (or too small as you say)?
>> I guess this is a limitation. Mapping on a page boundary shouldn't be
>> too much restrictive.
> 
> Yeah. I really ought to look more closely at what the flow of
> execution is here, because I think how it works right now
> is a bit weird and works as much by luck as by judgement
> (we can longjump out of the middle of translating code
> right back to the cpu-exec.c loop, and in some cases
> I think what happens is that we try to translate code,
> and as part of the "load didn't work" code path we
> nestedly try to translate the same thing again which
> of course fails again, only the second time around we
> realize and longjump out.
> 
> (At the moment for linux-user mode this is causing us to
> assert about taking the tb lock twice, because we hold
> the tb lock during translation and then try to grab it
> again to do the cpu_restore_state() in the signal handler.)
> 

Yes it seems there are some scary things happening there.

Fred

> thanks
> -- PMM
>