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). Alistair
