Hi Jan,

On Thu, May 19, 2022 at 12:39 PM Jan Kiszka <[email protected]> wrote:
>
> On 19.05.22 11:44, Lad, Prabhakar wrote:
> > On Thu, May 19, 2022 at 6:30 AM Jan Kiszka <[email protected]> wrote:
> >> Forgot: that cannot work. The call of arm_dcaches_flush will overwrite
> >> lr, thus the second ret will only return to where the first ret jumped
> >> to - endless loop. You would have to restore lr (x30) from x17 in
> >> arch_entry first:
> >>
> >> mov x30, x17
> >> ret
> >>
> > That did the trick thanks!
> >
> > diff --git a/hypervisor/arch/arm64/entry.S b/hypervisor/arch/arm64/entry.S
> > index a9cabf7f..7b340bd1 100644
> > --- a/hypervisor/arch/arm64/entry.S
> > +++ b/hypervisor/arch/arm64/entry.S
> > @@ -109,6 +109,8 @@ arch_entry:
> >         mov     x0, #LINUX_HVC_SET_VECTORS_LEGACY
> >  1:
> >         hvc     #0
> > +       mov x30, x17
> > +       ret
> >
> >         hvc     #0      /* bootstrap vectors enter EL2 at el2_entry */
> >         b       .       /* we don't expect to return here */
> >
> >
> > With the above diff I do get the below:
> >
> > [   42.980805] jailhouse: loading out-of-tree module taints kernel.
> > Reading configuration set:
> >   Root cell:     Renesas RZ/V2L SMARC (renesas-r9a07g054l2.cell)
> > Overlapping memory regions inside cell: None
> > Overlapping memory regions with hypervisor: None
> > Missing resource interceptions for architecture arm64: None
> > [   46.582588] obcode @arm_dcaches_flush: d53b0024
> > [   46.582616] obcode @arm_dcaches_flush: d53b0024
> > [   46.611311] The Jailhouse is opening.
> >
> > So it looks like something to do with the debug console. This has to
> > be poked in the dark or any easy way to debug?
>
> Well, we do not yet know what goes wrong. We do know that we can call
> into the hyp take-over stub and register Jailhouse with it. We do not
> know if we will then end up in Jailhouse in hyp mode and just lack
> console output or if we crash on entry already.
>
Right agreed.

> To move the uart console out of the picture: Did you already check if
> the driver you select in the Jailhouse config is actually one that
> should support the UART on your board? Next is to double check if poking
The UART on this platform is almost identical to
JAILHOUSE_CON_TYPE_SCIFA type, but with some differences which I have
patched to work on this platform.

> registers in the way the Jailhouse driver will do at the addresses you
> configured will work: Pull the code into the kernel module or even into
> a userspace application with /dev/mem raw register access and try out if
> that works in a "safe" environment (without hypervisor mode).
>
Sure will give that a shot, any pointers on doing this from userspace?

Cheers,
Prabhakar

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