Re: [Qemu-devel] [PATCH] rtc: placing RTC memory region outside BQL

[Peter Maydell <peter.maydell@linaro.org>]

On 1 February 2018 at 14:23, Paolo Bonzini <pbonzini@redhat.com> wrote:
> On 01/02/2018 08:47, Gonglei wrote:
>> diff --git a/hw/timer/mc146818rtc.c b/hw/timer/mc146818rtc.c
>> index 35a05a6..d9d99c5 100644
>> --- a/hw/timer/mc146818rtc.c
>> +++ b/hw/timer/mc146818rtc.c
>> @@ -986,6 +986,7 @@ static void rtc_realizefn(DeviceState *dev, Error **errp)
>>      qemu_register_suspend_notifier(&s->suspend_notifier);
>>
>>      memory_region_init_io(&s->io, OBJECT(s), &cmos_ops, s, "rtc", 2);
>> +    memory_region_clear_global_locking(&s->io);
>>      isa_register_ioport(isadev, &s->io, base);
>>
>>      qdev_set_legacy_instance_id(dev, base, 3);
>>
>
> This is not enough, you need to add a new lock or something like that.
> Otherwise two vCPUs can access the RTC together and make a mess.

Do you also need to do something to take the global lock before
raising the outbound IRQ line (since it might be connected to a device
that does need the global lock), or am I confused ?

thanks
-- PMM