Re: [PATCH v4 01/40] hw/isa: check for current_cpu before generating IRQ

[Philippe Mathieu-Daudé]

On 7/1/20 7:48 PM, Philippe Mathieu-Daudé wrote:
> +MST/Igor for ICH9
> 
> On 7/1/20 7:37 PM, Philippe Mathieu-Daudé wrote:
>> On 7/1/20 7:34 PM, Philippe Mathieu-Daudé wrote:
>>> +Paolo
>>>
>>> On 7/1/20 7:09 PM, Alex Bennée wrote:
>>>> Philippe Mathieu-Daudé <philmd@redhat.com> writes:
>>>>> On 7/1/20 6:40 PM, Alex Bennée wrote:
>>>>>> Philippe Mathieu-Daudé <philmd@redhat.com> writes:
>>>>>>
>>>>>>> On 7/1/20 3:56 PM, Alex Bennée wrote:
>>>>>>>> It's possible to trigger this function from qtest/monitor at which
>>>>>>>> point current_cpu won't point at the right place. Check it and
>>>>>>>> fall back to first_cpu if it's NULL.
>>>>>>>>
>>>>>>>> Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
>>>>>>>> Cc: Bug 1878645 <1878645@bugs.launchpad.net>
>>>>>>>> ---
>>>>>>>>  hw/isa/lpc_ich9.c | 2 +-
>>>>>>>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>>>>>>>
>>>>>>>> diff --git a/hw/isa/lpc_ich9.c b/hw/isa/lpc_ich9.c
>>>>>>>> index cd6e169d47a..791c878eb0b 100644
>>>>>>>> --- a/hw/isa/lpc_ich9.c
>>>>>>>> +++ b/hw/isa/lpc_ich9.c
>>>>>>>> @@ -439,7 +439,7 @@ static void ich9_apm_ctrl_changed(uint32_t val, 
>>>>>>>> void *arg)
>>>>>>>>                  cpu_interrupt(cs, CPU_INTERRUPT_SMI);
>>>>>>>>              }
>>>>>>>>          } else {
>>>>>>>> -            cpu_interrupt(current_cpu, CPU_INTERRUPT_SMI);
>>>>>>>> +            cpu_interrupt(current_cpu ? current_cpu : first_cpu, 
>>>>>>>> CPU_INTERRUPT_SMI);
>>>>>>>
>>>>>>> I'm not sure this change anything, as first_cpu is NULL when using
>>>>>>> qtest accelerator or none-machine, see 508b4ecc39 ("gdbstub.c: fix
>>>>>>> GDB connection segfault caused by empty machines").
>>>>>>
>>>>>> Good point - anyway feel free to ignore - it shouldn't have been in this
>>>>>> series. It was just some random experimentation I was doing when looking
>>>>>> at that bug.
>>>>>
>>>>> See commit c781a2cc42 ("hw/i386/vmport: Allow QTest use without
>>>>> crashing") for a similar approach, but here I was thinking about
>>>>> a more generic fix, not very intrusive:
>>>>>
>>>>> -- >8 --
>>>>> diff --git a/hw/isa/apm.c b/hw/isa/apm.c
>>>>> index bce266b957..809afeb3e4 100644
>>>>> --- a/hw/isa/apm.c
>>>>> +++ b/hw/isa/apm.c
>>>>> @@ -40,7 +40,7 @@ static void apm_ioport_writeb(void *opaque, hwaddr
>>>>> addr, uint64_t val,
>>>>>      if (addr == 0) {
>>>>>          apm->apmc = val;
>>>>>
>>>>> -        if (apm->callback) {
>>>>> +        if (apm->callback && !qtest_enabled()) {
>>>>>              (apm->callback)(val, apm->arg);
>>>>>          }
>>>>
>>>> But the other failure mode reported on the bug thread was via the
>>>> monitor - so I'm not sure just checking for qtest catches that.
>>>
>>> Ah indeed.
>>>
>>> in exec.c:
>>>
>>> /* current CPU in the current thread. It is only valid inside
>>>    cpu_exec() */
>>> __thread CPUState *current_cpu;
>>>
>>> Maybe we shouldn't use current_cpu out of exec.c...
>>
>> I meant, out of cpu_exec(), a cpu thread. Here we access it
>> from an I/O thread.

Ah! we are in the monitor thread... It makes sense there is not
current_cpu assigned :)

> 
> ARM and S390X use:
> 
> hw/arm/boot.c:460:    ARMCPU *armcpu = ARM_CPU(qemu_get_cpu(0));
> hw/arm/virt.c:331:    armcpu = ARM_CPU(qemu_get_cpu(0));
> hw/arm/virt.c:549:    armcpu = ARM_CPU(qemu_get_cpu(0));
> hw/cpu/a15mpcore.c:69:        cpuobj = OBJECT(qemu_get_cpu(0));
> hw/cpu/a9mpcore.c:76:    cpuobj = OBJECT(qemu_get_cpu(0));
> target/s390x/cpu_models.c:155:        cpu = S390_CPU(qemu_get_cpu(0));
> target/s390x/cpu_models.c:169:        cpu = S390_CPU(qemu_get_cpu(0));
> target/s390x/cpu_models.c:184:        cpu = S390_CPU(qemu_get_cpu(0));
> target/s390x/cpu_models.c:204:        cpu = S390_CPU(qemu_get_cpu(0));
> target/s390x/cpu_models.c:218:        cpu = S390_CPU(qemu_get_cpu(0));
> 
> It seems odd that the ICH9 delivers the SMI on a random core.
> Usually the IRQ lines are wired to a particular unit.
>