On 16/12/15 17:08, Daniel Thompson wrote: > SysRq-L does not generate a backtrace from all CPUs when I test it > on my Inforce IFC6410 platform (Snapdragon 600). The stack dump code, > triggered by IPI_CPU_BACKTRACE, never runs on the other CPUs. > Eventually we hit the 10 second timeout and a subset of the expected > stack dumps on are shown on the console. > > It is likely this is because SGI IDs 14 and 15 have been reserved for > use by secure world on this platform. For IFC6410 platform the code > works as expected when IPI_CPU_BACKTRACE is set to any value in the > interval 9..13. > > Signed-off-by: Daniel Thompson <daniel.thomp...@linaro.org> > --- > arch/arm/kernel/smp.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/arch/arm/kernel/smp.c b/arch/arm/kernel/smp.c > index b26361355dae..78205927fcd4 100644 > --- a/arch/arm/kernel/smp.c > +++ b/arch/arm/kernel/smp.c > @@ -73,7 +73,8 @@ enum ipi_msg_type { > IPI_CPU_STOP, > IPI_IRQ_WORK, > IPI_COMPLETION, > - IPI_CPU_BACKTRACE = 15, > + IPI_CPU_BACKTRACE = 13, > + /* 14 and 15 are reserved; they do not work on some Krait CPUs */ > }; > > static DECLARE_COMPLETION(cpu_running); >
It looks to me that we're just moving the goal posts and keep using a SGI that is likely to be reserved by the secure side. Quoting the GIC spec: In any system that implements the ARM Security Extensions, to support a consistent model for message passing between processors, ARM strongly recommends that all processors reserve: * ID0-ID7 for Non-secure interrupts * ID8-ID15 for Secure interrupts. Of course, this is only a recommendation, but it is one that is likely to be followed... Now, we are already using our 8 "non-secure" SGIs, but we can immediately reclaim one (IPI_CALL_FUNC_SINGLE is not that useful anymore). I'll cook a patch for that. Thanks, M. -- Jazz is not dead. It just smells funny... -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/