riscv: Enable context tracking
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> Signed-off-by: Palmer Dabbelt <palmerdabbelt@google.com>
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@ -53,6 +53,7 @@ config RISCV
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select HAVE_ARCH_SECCOMP_FILTER
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select HAVE_ARCH_TRACEHOOK
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select HAVE_ASM_MODVERSIONS
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select HAVE_CONTEXT_TRACKING
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select HAVE_COPY_THREAD_TLS
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select HAVE_DMA_CONTIGUOUS if MMU
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select HAVE_EBPF_JIT if MMU
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@ -100,6 +100,16 @@ _save_context:
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#ifdef CONFIG_TRACE_IRQFLAGS
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call trace_hardirqs_off
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#endif
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#ifdef CONFIG_CONTEXT_TRACKING
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/* If previous state is in user mode, call context_tracking_user_exit. */
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li a0, SR_PP
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and a0, s1, a0
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bnez a0, skip_context_tracking
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call context_tracking_user_exit
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skip_context_tracking:
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#endif
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/*
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* MSB of cause differentiates between
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* interrupts and exceptions
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@ -145,7 +155,7 @@ _save_context:
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tail do_trap_unknown
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handle_syscall:
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#ifdef CONFIG_TRACE_IRQFLAGS
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#if defined(CONFIG_TRACE_IRQFLAGS) || defined(CONFIG_CONTEXT_TRACKING)
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/* Recover a0 - a7 for system calls */
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REG_L a0, PT_A0(sp)
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REG_L a1, PT_A1(sp)
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@ -227,6 +237,10 @@ resume_userspace:
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andi s1, s0, _TIF_WORK_MASK
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bnez s1, work_pending
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#ifdef CONFIG_CONTEXT_TRACKING
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call context_tracking_user_enter
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#endif
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/* Save unwound kernel stack pointer in thread_info */
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addi s0, sp, PT_SIZE_ON_STACK
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REG_S s0, TASK_TI_KERNEL_SP(tp)
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