Messages in this thread Patch in this message | | | From | Greentime Hu <> | Subject | [PATCH 2/2] riscv: Enable context tracking | Date | Tue, 23 Jun 2020 21:28:52 +0800 |
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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.hu@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 + 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) -- 2.27.0
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