Messages in this thread | | | From | Greentime Hu <> | Date | Sun, 28 Jun 2020 22:23:54 +0800 | Subject | Re: [PATCH 2/2] riscv: Enable context tracking |
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guoren <guoren@linux.alibaba.com> 於 2020年6月27日 週六 上午12:29寫道: > > 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 > >
Hi Guo,
These registers are callee saved registers. I think callee will take care of it. https://github.com/riscv/riscv-elf-psabi-doc/blob/master/riscv-elf.md#integer-register-convention-
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