Re: [PATCH 4/5] ppc/spapr: Don't kill the guest if a recovered FWNMI machine check delivery fails

[Nicholas Piggin]

Greg Kurz's on March 18, 2020 2:57 am:
> On Tue, 17 Mar 2020 15:02:14 +1000
> Nicholas Piggin <address@hidden> wrote:
> 
>> Try to be tolerant of errors if the machine check had been recovered
>> by the host.
>> 
>> Signed-off-by: Nicholas Piggin <address@hidden>
>> ---
> 
> Same comment as previous patch on multi-line error strings and
> warn_report() in the !recovered case.
> 
>>  hw/ppc/spapr_events.c | 25 ++++++++++++++++++-------
>>  1 file changed, 18 insertions(+), 7 deletions(-)
>> 
>> diff --git a/hw/ppc/spapr_events.c b/hw/ppc/spapr_events.c
>> index d35151eeb0..3f524cb0ca 100644
>> --- a/hw/ppc/spapr_events.c
>> +++ b/hw/ppc/spapr_events.c
>> @@ -807,13 +807,20 @@ static void spapr_mce_dispatch_elog(PowerPCCPU *cpu, 
>> bool recovered)
>>      /* get rtas addr from fdt */
>>      rtas_addr = spapr_get_rtas_addr();
>>      if (!rtas_addr) {
>> -        warn_report("FWNMI: Unable to deliver machine check to guest: "
>> -                    "rtas_addr not found.");
>> -        qemu_system_guest_panicked(NULL);
>> +        if (!recovered) {
>> +            warn_report("FWNMI: Unable to deliver machine check to guest: "
>> +                        "rtas_addr not found.");
>> +            qemu_system_guest_panicked(NULL);
>> +        } else {
>> +            warn_report("FWNMI: Unable to deliver machine check to guest: "
>> +                        "rtas_addr not found. Machine check recovered.");
>> +        }
>>          g_free(ext_elog);
>>          return;
>>      }
>>  
>> +    spapr->fwnmi_machine_check_interlock = cpu->vcpu_id;
>> +
> 
> I don't understand this change.

If we bail out without delivering the interrupt, we can't take the
interlock otherwise the guest can never release it.

Thanks,
Nick