Re: [PATCH v1 09/14] xen/riscv: introduce do_unexpected_trap()

[Oleksii <oleksii.kurochko@xxxxxxxxx>]

On Mon, 2023-01-23 at 09:39 +1000, Alistair Francis wrote:
> On Sat, Jan 21, 2023 at 1:00 AM Oleksii Kurochko
> <oleksii.kurochko@xxxxxxxxx> wrote:
> > 
> > The patch introduces the function the purpose of which is to print
> > a cause of an exception and call "wfi" instruction.
> > 
> > Signed-off-by: Oleksii Kurochko <oleksii.kurochko@xxxxxxxxx>
> > ---
> >  xen/arch/riscv/traps.c | 14 +++++++++++++-
> >  1 file changed, 13 insertions(+), 1 deletion(-)
> > 
> > diff --git a/xen/arch/riscv/traps.c b/xen/arch/riscv/traps.c
> > index dd64f053a5..fc25138a4b 100644
> > --- a/xen/arch/riscv/traps.c
> > +++ b/xen/arch/riscv/traps.c
> > @@ -95,7 +95,19 @@ const char *decode_cause(unsigned long cause)
> >      return decode_trap_cause(cause);
> >  }
> > 
> > -void __handle_exception(struct cpu_user_regs *cpu_regs)
> > +static void do_unexpected_trap(const struct cpu_user_regs *regs)
> >  {
> > +    unsigned long cause = csr_read(CSR_SCAUSE);
> > +
> > +    early_printk("Unhandled exception: ");
> > +    early_printk(decode_cause(cause));
> > +    early_printk("\n");
> > +
> > +    // kind of die...
> >      wait_for_interrupt();
> 
> We could put this in a loop, to ensure we never progress
> 
I think that right now there is no big difference how to stop
because we have only 1 CPU, interrupts are disabled and we are in
exception so it looks like anything can interrupt us.
And in future it will be changed to panic() so we won't need here wfi()
any more.
> 

Oleksii