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. Alistair > > >> >> Thanks, >> Alistair >> >>> >>> Paolo >>> > > > -- > Alex Bennée >
