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

[Philippe Mathieu-Daudé]

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);
         }
     } else {
---