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

[Thomas Huth <thuth@redhat.com>]

On 15/05/2023 14.48, Frederic Barrat wrote:
> 
> 
> On 11/05/2023 11:15, Alexander Bulekov wrote:
>> 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.
> 
> Hello,
> 
> I was also started hitting it, with machine powernv10. And indeed, disabling 
> the check on both lpc_hc_regs and opb_master_regs should be all we need (and 
> it's working fine for me).

Alexander, could you please respin your patch to fix the opb_master_regs, too?

  Thomas