Re: [PATCH] pnv_lpc: disable reentrancy detection for lpc-hc

[Alexander Bulekov]

On 230511 1104, Cédric Le Goater wrote:
> Hello Alexander
> 
> On 5/11/23 10:53, Alexander Bulekov wrote:
> > As lpc-hc is designed for re-entrant calls from xscom, mark it
> > re-entrancy safe.
> > 
> > Reported-by: Thomas Huth <thuth@redhat.com>
> > Signed-off-by: Alexander Bulekov <alxndr@bu.edu>
> > ---
> >   hw/ppc/pnv_lpc.c | 2 ++
> >   1 file changed, 2 insertions(+)
> > 
> > diff --git a/hw/ppc/pnv_lpc.c b/hw/ppc/pnv_lpc.c
> > index 01f44c19eb..67fd049a7f 100644
> > --- a/hw/ppc/pnv_lpc.c
> > +++ b/hw/ppc/pnv_lpc.c
> > @@ -738,6 +738,8 @@ static void pnv_lpc_realize(DeviceState *dev, Error 
> > **errp)
> >                                   &lpc->opb_master_regs);
> >       memory_region_init_io(&lpc->lpc_hc_regs, OBJECT(dev), &lpc_hc_ops, 
> > lpc,
> >                             "lpc-hc", LPC_HC_REGS_OPB_SIZE);
> > +    /* xscom writes to lpc-hc. As such mark lpc-hc re-entrancy safe */
> > +    lpc->lpc_hc_regs.disable_reentrancy_guard = true;
> >       memory_region_add_subregion(&lpc->opb_mr, LPC_HC_REGS_OPB_ADDR,
> >                                   &lpc->lpc_hc_regs);
> 
> The warning changed :
> 
>   qemu-system-ppc64: warning: Blocked re-entrant IO on MemoryRegion: 
> lpc-opb-master at addr: 0x8
> 
> I will take a look unless you know exactly what to do.
>

That does not show up for me with "./qemu-system-ppc64 -M powernv8" 
Do I need to boot a kernel to see the message?

I was worried that there might be other re-entrant IO in this device.
Maybe there should be a way to just mark the whole device re-entrancy
safe.