Messages in this thread Patch in this message | | | Date | Sat, 27 Jun 2020 00:28:38 +0800 | From | "guoren" <> | Subject | Re: [PATCH 2/2] riscv: Enable context tracking |
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Hi Greentime,
On 2020/6/23 9:28 下午, Greentime Hu 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.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
It will destroy s1-s5 which are used in entry.S like these:
REG_S s0, PT_SP(sp) REG_S s1, PT_STATUS(sp) REG_S s2, PT_EPC(sp) REG_S s3, PT_BADADDR(sp) REG_S s4, PT_CAUSE(sp) REG_S s5, PT_TP(sp) ... /* * MSB of cause differentiates between * interrupts and exceptions */ bge s4, zero, 1f
...
/* * Exceptions run with interrupts enabled or disabled depending on the * state of SR_PIE in m/sstatus. */ andi t0, s1, SR_PIE
...
/* Handle syscalls */ li t0, EXC_SYSCALL beq s4, t0, handle_syscall
...
I also solved it in my lockdep patches, please have a look: https://lore.kernel.org/linux-riscv/1592323021-98541-4-git-send-email-guoren@kernel.org/T/#u
Best Regards
Guo Ren
> + > +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) | |