[patch V4 13/15] x86/entry: Use generic interrupt entry/exit code

Thomas Gleixner
2020-07-21T11:09:19Z

Replace the x86 code with the generic variant. Use temporary defines for
idtentry_* which will be cleaned up in the next step.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
arch/x86/entry/common.c | 167 ----------------------------------------
arch/x86/include/asm/idtentry.h | 10 --
2 files changed, 5 insertions(+), 172 deletions(-)

--- a/arch/x86/entry/common.c
+++ b/arch/x86/entry/common.c
@@ -198,171 +198,6 @@ SYSCALL_DEFINE0(ni_syscall)
return -ENOSYS;
}

-/**
- * idtentry_enter - Handle state tracking on ordinary idtentries
- * @regs: Pointer to pt_regs of interrupted context
- *
- * Invokes:
- * - lockdep irqflag state tracking as low level ASM entry disabled
- * interrupts.
- *
- * - Context tracking if the exception hit user mode.
- *
- * - The hardirq tracer to keep the state consistent as low level ASM
- * entry disabled interrupts.
- *
- * As a precondition, this requires that the entry came from user mode,
- * idle, or a kernel context in which RCU is watching.
- *
- * For kernel mode entries RCU handling is done conditional. If RCU is
- * watching then the only RCU requirement is to check whether the tick has
- * to be restarted. If RCU is not watching then rcu_irq_enter() has to be
- * invoked on entry and rcu_irq_exit() on exit.
- *
- * Avoiding the rcu_irq_enter/exit() calls is an optimization but also
- * solves the problem of kernel mode pagefaults which can schedule, which
- * is not possible after invoking rcu_irq_enter() without undoing it.
- *
- * For user mode entries irqentry_enter_from_user_mode() must be invoked to
- * establish the proper context for NOHZ_FULL. Otherwise scheduling on exit
- * would not be possible.
- *
- * Returns: An opaque object that must be passed to idtentry_exit()
- *
- * The return value must be fed into the state argument of
- * idtentry_exit().
- */
-idtentry_state_t noinstr idtentry_enter(struct pt_regs *regs)
-{
- idtentry_state_t ret = {
- .exit_rcu = false,
- };
-
- if (user_mode(regs)) {
- irqentry_enter_from_user_mode(regs);
- return ret;
- }
-
- /*
- * If this entry hit the idle task invoke rcu_irq_enter() whether
- * RCU is watching or not.
- *
- * Interupts can nest when the first interrupt invokes softirq
- * processing on return which enables interrupts.
- *
- * Scheduler ticks in the idle task can mark quiescent state and
- * terminate a grace period, if and only if the timer interrupt is
- * not nested into another interrupt.
- *
- * Checking for __rcu_is_watching() here would prevent the nesting
- * interrupt to invoke rcu_irq_enter(). If that nested interrupt is
- * the tick then rcu_flavor_sched_clock_irq() would wrongfully
- * assume that it is the first interupt and eventually claim
- * quiescient state and end grace periods prematurely.
- *
- * Unconditionally invoke rcu_irq_enter() so RCU state stays
- * consistent.
- *
- * TINY_RCU does not support EQS, so let the compiler eliminate
- * this part when enabled.
- */
- if (!IS_ENABLED(CONFIG_TINY_RCU) && is_idle_task(current)) {
- /*
- * If RCU is not watching then the same careful
- * sequence vs. lockdep and tracing is required
- * as in irqentry_enter_from_user_mode().
- */
- lockdep_hardirqs_off(CALLER_ADDR0);
- rcu_irq_enter();
- instrumentation_begin();
- trace_hardirqs_off_finish();
- instrumentation_end();
-
- ret.exit_rcu = true;
- return ret;
- }
-
- /*
- * If RCU is watching then RCU only wants to check whether it needs
- * to restart the tick in NOHZ mode. rcu_irq_enter_check_tick()
- * already contains a warning when RCU is not watching, so no point
- * in having another one here.
- */
- instrumentation_begin();
- rcu_irq_enter_check_tick();
- /* Use the combo lockdep/tracing function */
- trace_hardirqs_off();
- instrumentation_end();
-
- return ret;
-}
-
-static void idtentry_exit_cond_resched(struct pt_regs *regs, bool may_sched)
-{
- if (may_sched && !preempt_count()) {
- /* Sanity check RCU and thread stack */
- rcu_irq_exit_check_preempt();
- if (IS_ENABLED(CONFIG_DEBUG_ENTRY))
- WARN_ON_ONCE(!on_thread_stack());
- if (need_resched())
- preempt_schedule_irq();
- }
- /* Covers both tracing and lockdep */
- trace_hardirqs_on();
-}
-
-/**
- * idtentry_exit - Handle return from exception that used idtentry_enter()
- * @regs: Pointer to pt_regs (exception entry regs)
- * @state: Return value from matching call to idtentry_enter()
- *
- * Depending on the return target (kernel/user) this runs the necessary
- * preemption and work checks if possible and reguired and returns to
- * the caller with interrupts disabled and no further work pending.
- *
- * This is the last action before returning to the low level ASM code which
- * just needs to return to the appropriate context.
- *
- * Counterpart to idtentry_enter(). The return value of the entry
- * function must be fed into the @state argument.
- */
-void noinstr idtentry_exit(struct pt_regs *regs, idtentry_state_t state)
-{
- lockdep_assert_irqs_disabled();
-
- /* Check whether this returns to user mode */
- if (user_mode(regs)) {
- irqentry_exit_to_user_mode(regs);
- } else if (regs->flags & X86_EFLAGS_IF) {
- /*
- * If RCU was not watching on entry this needs to be done
- * carefully and needs the same ordering of lockdep/tracing
- * and RCU as the return to user mode path.
- */
- if (state.exit_rcu) {
- instrumentation_begin();
- /* Tell the tracer that IRET will enable interrupts */
- trace_hardirqs_on_prepare();
- lockdep_hardirqs_on_prepare(CALLER_ADDR0);
- instrumentation_end();
- rcu_irq_exit();
- lockdep_hardirqs_on(CALLER_ADDR0);
- return;
- }
-
- instrumentation_begin();
- idtentry_exit_cond_resched(regs, IS_ENABLED(CONFIG_PREEMPTION));
- instrumentation_end();
- } else {
- /*
- * IRQ flags state is correct already. Just tell RCU if it
- * was not watching on entry.
- */
- if (state.exit_rcu)
- rcu_irq_exit();
- }
-}
-
#ifdef CONFIG_XEN_PV
#ifndef CONFIG_PREEMPTION
/*
@@ -427,7 +262,7 @@ static void __xen_pv_evtchn_do_upcall(vo
inhcall = get_and_clear_inhcall();
if (inhcall && !WARN_ON_ONCE(state.exit_rcu)) {
instrumentation_begin();
- idtentry_exit_cond_resched(regs, true);
+ irqentry_exit_cond_resched();
instrumentation_end();
restore_inhcall(inhcall);
} else {
--- a/arch/x86/include/asm/idtentry.h
+++ b/arch/x86/include/asm/idtentry.h
@@ -11,12 +11,10 @@

#include <asm/irq_stack.h>

-typedef struct idtentry_state {
- bool exit_rcu;
-} idtentry_state_t;
-
-idtentry_state_t idtentry_enter(struct pt_regs *regs);
-void idtentry_exit(struct pt_regs *regs, idtentry_state_t state);
+/* Temporary defines */
+typedef irqentry_state_t idtentry_state_t;
+#define idtentry_enter irqentry_enter
+#define idtentry_exit irqentry_exit

/**
* DECLARE_IDTENTRY - Declare functions for simple IDT entry points