Re: [Qemu-devel] [PATCH v1 5/5] hw/arm: Add the Netduino Plus 2

[Alistair Francis]

On Fri, May 3, 2019 at 9:26 PM Alistair <address@hidden> wrote:
>
> On Thu, May 2, 2019, at 3:06 AM, Peter Maydell wrote:
> > On Tue, 30 Apr 2019 at 21:29, Alistair Francis <address@hidden> wrote:
> > >
> > > On Tue, Apr 30, 2019 at 9:02 AM Peter Maydell <address@hidden> wrote:
> > > > Can you explain the purpose of the reset code? None of the other
> > > > v7m boards seem to need to do a manual qemu_register_reset().
> > >
> > > The reset code allows the machine to work with the -kernel option.
> > > Without the reset override using -kernel results in the guest starting
> > > at the wrong address. We can use the -device loader option without the
> > > reset code though.
> >
> > That sounds in line with how -kernel works on the other armv7m
> > boards -- the expectation is that your image file includes a
> > full vector table and the CPU will read the PC and SP from it
> > when it resets. If you want "honour the entry point" you can
> > use -device loader, as you say.
> >
> > Ignoring the entry point for -kernel ELF files is certainly
> > a bit confusing, but I think if we want to change this we should
> > do it globally, rather than having one board which behaves
> > differently to the rest. Changing it does have some awkwardness:
>
> Hmm... That is a good point. It is confusing having something just for one 
> board. I'll drop this part and we can re-evaluate later.
>
> > * possibility of breaking previously working images
>
> I have no way to test the other boards, so this might be difficult to change.
>
> > * we can get the initial PC from the ELF entrypoint, but if
> >  we do this what do we do about the initial SP value ?
>
> Not sure about this one either. I'm guessing it changes between the different 
> M cores.

Ah, it seems like -device loader doesn't work, it looks like not
setting the thumb register causes this core dump:

qemu: fatal: Lockup: can't escalate 3 to HardFault (current priority -1)

R00=20000000 R01=00000574 R02=200015d0 R03=200015d0
R04=00000000 R05=00000000 R06=00000000 R07=00000000
R08=00000000 R09=00000000 R10=00000000 R11=00000000
R12=00000000 R13=ffffffe0 R14=fffffff9 R15=0800cba4
XPSR=61000003 -ZC- T handler
s00=00000000 s01=00000000 d00=0000000000000000
s02=00000000 s03=00000000 d01=0000000000000000
s04=00000000 s05=00000000 d02=0000000000000000
s06=00000000 s07=00000000 d03=0000000000000000
s08=00000000 s09=00000000 d04=0000000000000000
s10=00000000 s11=00000000 d05=0000000000000000
s12=00000000 s13=00000000 d06=0000000000000000
s14=00000000 s15=00000000 d07=0000000000000000
s16=00000000 s17=00000000 d08=0000000000000000
s18=00000000 s19=00000000 d09=0000000000000000
s20=00000000 s21=00000000 d10=0000000000000000
s22=00000000 s23=00000000 d11=0000000000000000
s24=00000000 s25=00000000 d12=0000000000000000
s26=00000000 s27=00000000 d13=0000000000000000
s28=00000000 s29=00000000 d14=0000000000000000
s30=00000000 s31=00000000 d15=0000000000000000
s32=00000000 s33=00000000 d16=0000000000000000
s34=00000000 s35=00000000 d17=0000000000000000
s36=00000000 s37=00000000 d18=0000000000000000
s38=00000000 s39=00000000 d19=0000000000000000
s40=00000000 s41=00000000 d20=0000000000000000
s42=00000000 s43=00000000 d21=0000000000000000
s44=00000000 s45=00000000 d22=0000000000000000
s46=00000000 s47=00000000 d23=0000000000000000
s48=00000000 s49=00000000 d24=0000000000000000
s50=00000000 s51=00000000 d25=0000000000000000
s52=00000000 s53=00000000 d26=0000000000000000
s54=00000000 s55=00000000 d27=0000000000000000
s56=00000000 s57=00000000 d28=0000000000000000
s58=00000000 s59=00000000 d29=0000000000000000
s60=00000000 s61=00000000 d30=0000000000000000
s62=00000000 s63=00000000 d31=0000000000000000
FPSCR: 00000000
Aborted (core dumped)

Alistair

>
> Alistair
>
> >
> > thanks
> > -- PMM
> >
> >
>