Palmer Dabbelt <pal...@dabbelt.com> 於 2020年7月11日 週六 上午1:30寫道： > > On Wed, 24 Jun 2020 02:03:16 PDT (-0700), greentime...@sifive.com wrote: > > This patch implements and enables context tracking for riscv (which is a > > prerequisite for CONFIG_NO_HZ_FULL support) > > > > It adds checking for previous state in the entry that all excepttions and > > interrupts goes to and calls context_tracking_user_exit() if it comes from > > user space. It also calls context_tracking_user_enter() if it will return > > to user space before restore_all. > > > > This patch is tested with the dynticks-testing testcase in > > qemu-system-riscv64 virt machine and Unleashed board. > > git://git.kernel.org/pub/scm/linux/kernel/git/frederic/dynticks-testing.git > > > > We can see the log here. The tick got mostly stopped during the execution > > of the user loop. > > > > _-----=> irqs-off > > / _----=> need-resched > > | / _---=> hardirq/softirq > > || / _--=> preempt-depth > > ||| / delay > > TASK-PID CPU# |||| TIMESTAMP FUNCTION > > | | | |||| | | > > <idle>-0 [001] d..2 604.183512: sched_switch: prev_comm=swapper/1 > > prev_pid=0 prev_prio=120 prev_state=R ==> next_comm=taskset next_pid=273 > > next_prio=120 > > user_loop-273 [001] d.h1 604.184788: hrtimer_expire_entry: > > hrtimer=000000002eda5fab function=tick_sched_timer now=604176096300 > > user_loop-273 [001] d.s2 604.184897: workqueue_queue_work: work > > struct=00000000383402c2 function=vmstat_update workqueue=00000000f36d35d4 > > req_cpu=1 cpu=1 > > user_loop-273 [001] dns2 604.185039: tick_stop: success=0 > > dependency=SCHED > > user_loop-273 [001] dn.1 604.185103: tick_stop: success=0 > > dependency=SCHED > > user_loop-273 [001] d..2 604.185154: sched_switch: prev_comm=taskset > > prev_pid=273 prev_prio=120 prev_state=R+ ==> next_comm=kworker/1:1 > > next_pid=46 next_prio=120 > > <...>-46 [001] .... 604.185194: workqueue_execute_start: work > > struct 00000000383402c2: function vmstat_update > > <...>-46 [001] d..2 604.185266: sched_switch: > > prev_comm=kworker/1:1 prev_pid=46 prev_prio=120 prev_state=I ==> > > next_comm=taskset next_pid=273 next_prio=120 > > user_loop-273 [001] d.h1 604.188812: hrtimer_expire_entry: > > hrtimer=000000002eda5fab function=tick_sched_timer now=604180133400 > > user_loop-273 [001] d..1 604.189050: tick_stop: success=1 > > dependency=NONE > > user_loop-273 [001] d..2 614.251386: sched_switch: prev_comm=user_loop > > prev_pid=273 prev_prio=120 prev_state=X ==> next_comm=swapper/1 next_pid=0 > > next_prio=120 > > <idle>-0 [001] d..2 614.315391: sched_switch: prev_comm=swapper/1 > > prev_pid=0 prev_prio=120 prev_state=R ==> next_comm=taskset next_pid=276 > > next_prio=120 > > > > Signed-off-by: Greentime Hu <greentime...@sifive.com> > > --- > > arch/riscv/Kconfig | 1 + > > arch/riscv/kernel/entry.S | 23 +++++++++++++++++++++++ > > 2 files changed, 24 insertions(+) > > > > diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig > > index 128192e14ff2..17520e11815b 100644 > > --- a/arch/riscv/Kconfig > > +++ b/arch/riscv/Kconfig > > @@ -52,6 +52,7 @@ config RISCV > > select HAVE_ARCH_SECCOMP_FILTER > > select HAVE_ARCH_TRACEHOOK > > select HAVE_ASM_MODVERSIONS > > + select HAVE_CONTEXT_TRACKING > > select HAVE_COPY_THREAD_TLS > > select HAVE_DMA_CONTIGUOUS if MMU > > select HAVE_EBPF_JIT if MMU > > diff --git a/arch/riscv/kernel/entry.S b/arch/riscv/kernel/entry.S > > index cae7e6d4c7ef..6ed579fc1073 100644 > > --- a/arch/riscv/kernel/entry.S > > +++ b/arch/riscv/kernel/entry.S > > @@ -97,6 +97,14 @@ _save_context: > > la gp, __global_pointer$ > > .option pop > > > > +#ifdef CONFIG_CONTEXT_TRACKING > > + /* If previous state is in user mode, call > > context_tracking_user_exit. */ > > + andi a0, s1, SR_SPP > > I've changed that to SR_PP, as I don't see any reason why this should depend > on > MMU. > > I think this is correct: we're using scratch==0 elsewhere to detect recursive > traps, but we've blown that away by this point so it's not an option. I don't > know of any reason why PP wouldn't be accurate.
Hi Palmer, Thank you. That makes sense to me. > > > + bnez a0, skip_context_tracking > > + call context_tracking_user_exit > > + > > +skip_context_tracking: > > +#endif > > la ra, ret_from_exception > > /* > > * MSB of cause differentiates between > > @@ -137,6 +145,17 @@ _save_context: > > tail do_trap_unknown > > > > handle_syscall: > > +#ifdef CONFIG_CONTEXT_TRACKING > > + /* Recover a0 - a7 for system calls */ > > + REG_L x10, PT_A0(sp) > > + REG_L x11, PT_A1(sp) > > + REG_L x12, PT_A2(sp) > > + REG_L x13, PT_A3(sp) > > + REG_L x14, PT_A4(sp) > > + REG_L x15, PT_A5(sp) > > + REG_L x16, PT_A6(sp) > > + REG_L x17, PT_A7(sp) > > +#endif > > /* save the initial A0 value (needed in signal handlers) */ > > REG_S a0, PT_ORIG_A0(sp) > > /* > > @@ -205,6 +224,10 @@ resume_userspace: > > andi s1, s0, _TIF_WORK_MASK > > bnez s1, work_pending > > > > +#ifdef CONFIG_CONTEXT_TRACKING > > + call context_tracking_user_enter > > +#endif > > + > > /* Save unwound kernel stack pointer in thread_info */ > > addi s0, sp, PT_SIZE_ON_STACK > > REG_S s0, TASK_TI_KERNEL_SP(tp)
