On Fri, Feb 2, 2018 at 12:37 PM, Alex Bennée <alex.ben...@linaro.org> wrote:
>
> Alistair Francis <alistair.fran...@xilinx.com> writes:
>
>> On Thu, Feb 1, 2018 at 9:13 AM, Alistair Francis
>> <alistair.fran...@xilinx.com> wrote:
>>> On Thu, Feb 1, 2018 at 4:01 AM, Alex Bennée <alex.ben...@linaro.org> wrote:
>>>>
>>>> Alistair Francis <alistair.fran...@xilinx.com> writes:
>>>>
>>>>> On Wed, Jan 31, 2018 at 12:32 PM, Alex Bennée <alex.ben...@linaro.org>
>>>>> wrote:
>>>>>>
>>>>>> Alistair Francis <alistair.fran...@xilinx.com> writes:
>>>>>>
>>>>>>> On Tue, Jan 30, 2018 at 8:26 PM, Paolo Bonzini <pbonz...@redhat.com>
>>>>>>> wrote:
>>>>>>>> On 30/01/2018 18:56, Alistair Francis wrote:
>>>>>>>>>
>>>>>>>>> I don't have a good solution though, as setting CPU_INTERRUPT_RESET
>>>>>>>>> doesn't help (that isn't handled while we are halted) and
>>>>>>>>> async_run_on_cpu()/run_on_cpu() doesn't reliably reset the CPU when we
>>>>>>>>> want.
>>>>>>>>>
>>>>>>>>> I've ever tried pausing all CPUs before reseting the CPU and them
>>>>>>>>> resuming them all but that doesn't seem to to work either.
>>>>>>>>
>>>>>>>> async_safe_run_on_cpu would be like async_run_on_cpu, except that it
>>>>>>>> takes care of stopping all other CPUs while the function runs.
>>>>>>>>
>>>>>>>>> Is there
>>>>>>>>> anything I'm missing? Is there no reliable way to reset a CPU?
>>>>>>>>
>>>>>>>> What do you mean by reliable? Executing no instruction after the one
>>>>>>>> you were at?
>>>>>>>
>>>>>>> The reset is called by a GPIO line, so I need the reset to be called
>>>>>>> basically as quickly as the GPIO line changes. The async_ and
>>>>>>> async_safe_ functions seem to not run quickly enough, even if I run a
>>>>>>> process_work_queue() function afterwards.
>>>>>>>
>>>>>>> Is there a way to kick the CPU to act on the async_*?
>>>>>>
>>>>>> Define quickly enough? The async_(safe) functions kick the vCPUs so they
>>>>>> will all exit the run loop as they enter the next TB (even if they loop
>>>>>> to themselves).
>>>>>
>>>>> We have a special power controller CPU that wakes all the CPUs up and
>>>>> at boot the async_* functions don't wake the CPUs up. If I just use
>>>>> the cpu_rest() function directly everything starts fine (but then I
>>>>> hit issues later).
>>>>>
>>>>> If I forcefully run process_queued_cpu_work() then I can get the CPUs
>>>>> up, but I don't think that is the right solution.
>>>>>
>>>>>>
>>>>>> From an external vCPUs point of view those extra instructions have
>>>>>> already executed. If the resetting vCPU needs them to have reset by the
>>>>>> time it executes it's next instruction it should either cpu_loop_exit at
>>>>>> that point or ensure it is the last instruction in it's TB (which is
>>>>>> what we do for the MMU flush cases in ARM, they all end the TB at that
>>>>>> point).
>>>>>
>>>>> cpu_loop_exit() sounds like it would help, but as I'm not in the CPU
>>>>> context it just seg faults.
>>>>
>>>> What context are you in? gdb-stub does have to something like this.
>>>
>>> gdb-stub just seems to use vm_stop() and vm_start().
>>>
>>> That fixes all hangs/asserts, but now Linux only brings up 1 CPU (instead
>>> of 4).
>>
>> Hmmm... Interesting if I do this on reset events:
>>
>> pause_all_vcpus();
>> cpu_reset(cpu);
>> resume_all_vcpus();
>>
>> it hangs, while if I do this
>>
>> if (runstate_is_running()) {
>> vm_stop(RUN_STATE_PAUSED);
>> }
>> cpu_reset(cpu);
>> if (!runstate_needs_reset()) {
>> vm_start();
>> }
>>
>> it doesn't hang but CPU bringup doesn't work.
>
> Hmm I'm still confused what context you are in. Is this an externally
> triggered reset via the (qemu) prompt or something?
This gets called from a variety of places. But most likely it's called
from a second QEMU process that is triggering an interrupt through a
device.
Alistair
>
>>
>> Alistair
>>
>>>
>>> Alistair
>
>
> --
> Alex Bennée
>
