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

["Cédric Le Goater" <clg@redhat.com>]

On 5/26/23 09:06, Thomas Huth wrote:
> 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?

I will do it.

C.