[PATCH V3.1] entry: Pass irqentry_state_t by reference

[ira.weiny@intel.com]

From: Ira Weiny <ira.weiny@intel.com>

Currently struct irqentry_state_t only contains a single bool value
which makes passing it by value is reasonable.  However, future patches
add information to this struct.  This includes the PKRS thread state,
included in this series, as well as information to store kmap reference
tracking and PKS global state outside this series.  In total, we
anticipate 2 new 32 bit fields and an integer field to be added to the
struct beyond the existing bool value.

Adding information to irqentry_state_t makes passing by value less
efficient.  Therefore, change the entry/exit calls to pass irq_state by
reference in preparation for the changes which follow.

While at it, make the code easier to follow by changing all the usage
sites to consistently use the variable name 'irq_state'.

Signed-off-by: Ira Weiny <ira.weiny@intel.com>

---
Changes from V3
	Clarify commit message regarding the need for this patch

Changes from V1
	From Thomas: Update commit message
	Further clean up Kernel doc and comments
		Missed some 'return' comments which are no longer valid

Changes from RFC V3
	Clean up @irq_state comments
	Standardize on 'irq_state' for the state variable name
	Refactor based on new patch from Thomas Gleixner
		Also addresses Peter Zijlstra's comment
---
 arch/x86/entry/common.c         |  8 ++++----
 arch/x86/include/asm/idtentry.h | 25 ++++++++++++++----------
 arch/x86/kernel/cpu/mce/core.c  |  4 ++--
 arch/x86/kernel/kvm.c           |  6 +++---
 arch/x86/kernel/nmi.c           |  4 ++--
 arch/x86/kernel/traps.c         | 21 ++++++++++++--------
 arch/x86/mm/fault.c             |  6 +++---
 include/linux/entry-common.h    | 18 +++++++++--------
 kernel/entry/common.c           | 34 +++++++++++++--------------------
 9 files changed, 65 insertions(+), 61 deletions(-)

diff --git a/arch/x86/entry/common.c b/arch/x86/entry/common.c
index 18d8f17f755c..87dea56a15d2 100644
--- a/arch/x86/entry/common.c
+++ b/arch/x86/entry/common.c
@@ -259,9 +259,9 @@ __visible noinstr void xen_pv_evtchn_do_upcall(struct pt_regs *regs)
 {
 	struct pt_regs *old_regs;
 	bool inhcall;
-	irqentry_state_t state;
+	irqentry_state_t irq_state;
 
-	state = irqentry_enter(regs);
+	irqentry_enter(regs, &irq_state);
 	old_regs = set_irq_regs(regs);
 
 	instrumentation_begin();
@@ -271,13 +271,13 @@ __visible noinstr void xen_pv_evtchn_do_upcall(struct pt_regs *regs)
 	set_irq_regs(old_regs);
 
 	inhcall = get_and_clear_inhcall();
-	if (inhcall && !WARN_ON_ONCE(state.exit_rcu)) {
+	if (inhcall && !WARN_ON_ONCE(irq_state.exit_rcu)) {
 		instrumentation_begin();
 		irqentry_exit_cond_resched();
 		instrumentation_end();
 		restore_inhcall(inhcall);
 	} else {
-		irqentry_exit(regs, state);
+		irqentry_exit(regs, &irq_state);
 	}
 }
 #endif /* CONFIG_XEN_PV */
diff --git a/arch/x86/include/asm/idtentry.h b/arch/x86/include/asm/idtentry.h
index 247a60a47331..282d2413b6a1 100644
--- a/arch/x86/include/asm/idtentry.h
+++ b/arch/x86/include/asm/idtentry.h
@@ -49,12 +49,13 @@ static __always_inline void __##func(struct pt_regs *regs);		\
 									\
 __visible noinstr void func(struct pt_regs *regs)			\
 {									\
-	irqentry_state_t state = irqentry_enter(regs);			\
+	irqentry_state_t irq_state;						\
 									\
+	irqentry_enter(regs, &irq_state);					\
 	instrumentation_begin();					\
 	__##func (regs);						\
 	instrumentation_end();						\
-	irqentry_exit(regs, state);					\
+	irqentry_exit(regs, &irq_state);					\
 }									\
 									\
 static __always_inline void __##func(struct pt_regs *regs)
@@ -96,12 +97,13 @@ static __always_inline void __##func(struct pt_regs *regs,		\
 __visible noinstr void func(struct pt_regs *regs,			\
 			    unsigned long error_code)			\
 {									\
-	irqentry_state_t state = irqentry_enter(regs);			\
+	irqentry_state_t irq_state;						\
 									\
+	irqentry_enter(regs, &irq_state);					\
 	instrumentation_begin();					\
 	__##func (regs, error_code);					\
 	instrumentation_end();						\
-	irqentry_exit(regs, state);					\
+	irqentry_exit(regs, &irq_state);					\
 }									\
 									\
 static __always_inline void __##func(struct pt_regs *regs,		\
@@ -192,15 +194,16 @@ static __always_inline void __##func(struct pt_regs *regs, u8 vector);	\
 __visible noinstr void func(struct pt_regs *regs,			\
 			    unsigned long error_code)			\
 {									\
-	irqentry_state_t state = irqentry_enter(regs);			\
+	irqentry_state_t irq_state;						\
 									\
+	irqentry_enter(regs, &irq_state);					\
 	instrumentation_begin();					\
 	irq_enter_rcu();						\
 	kvm_set_cpu_l1tf_flush_l1d();					\
 	__##func (regs, (u8)error_code);				\
 	irq_exit_rcu();							\
 	instrumentation_end();						\
-	irqentry_exit(regs, state);					\
+	irqentry_exit(regs, &irq_state);					\
 }									\
 									\
 static __always_inline void __##func(struct pt_regs *regs, u8 vector)
@@ -234,15 +237,16 @@ static void __##func(struct pt_regs *regs);				\
 									\
 __visible noinstr void func(struct pt_regs *regs)			\
 {									\
-	irqentry_state_t state = irqentry_enter(regs);			\
+	irqentry_state_t irq_state;						\
 									\
+	irqentry_enter(regs, &irq_state);					\
 	instrumentation_begin();					\
 	irq_enter_rcu();						\
 	kvm_set_cpu_l1tf_flush_l1d();					\
 	run_sysvec_on_irqstack_cond(__##func, regs);			\
 	irq_exit_rcu();							\
 	instrumentation_end();						\
-	irqentry_exit(regs, state);					\
+	irqentry_exit(regs, &irq_state);					\
 }									\
 									\
 static noinline void __##func(struct pt_regs *regs)
@@ -263,15 +267,16 @@ static __always_inline void __##func(struct pt_regs *regs);		\
 									\
 __visible noinstr void func(struct pt_regs *regs)			\
 {									\
-	irqentry_state_t state = irqentry_enter(regs);			\
+	irqentry_state_t irq_state;						\
 									\
+	irqentry_enter(regs, &irq_state);					\
 	instrumentation_begin();					\
 	__irq_enter_raw();						\
 	kvm_set_cpu_l1tf_flush_l1d();					\
 	__##func (regs);						\
 	__irq_exit_raw();						\
 	instrumentation_end();						\
-	irqentry_exit(regs, state);					\
+	irqentry_exit(regs, &irq_state);					\
 }									\
 									\
 static __always_inline void __##func(struct pt_regs *regs)
diff --git a/arch/x86/kernel/cpu/mce/core.c b/arch/x86/kernel/cpu/mce/core.c
index f5c860b1a50b..6ed2fa2ea321 100644
--- a/arch/x86/kernel/cpu/mce/core.c
+++ b/arch/x86/kernel/cpu/mce/core.c
@@ -1995,7 +1995,7 @@ static __always_inline void exc_machine_check_kernel(struct pt_regs *regs)
 	    mce_check_crashing_cpu())
 		return;
 
-	irq_state = irqentry_nmi_enter(regs);
+	irqentry_nmi_enter(regs, &irq_state);
 	/*
 	 * The call targets are marked noinstr, but objtool can't figure
 	 * that out because it's an indirect call. Annotate it.
@@ -2006,7 +2006,7 @@ static __always_inline void exc_machine_check_kernel(struct pt_regs *regs)
 	if (regs->flags & X86_EFLAGS_IF)
 		trace_hardirqs_on_prepare();
 	instrumentation_end();
-	irqentry_nmi_exit(regs, irq_state);
+	irqentry_nmi_exit(regs, &irq_state);
 }
 
 static __always_inline void exc_machine_check_user(struct pt_regs *regs)
diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
index 7f57ede3cb8e..ed7427c6e74d 100644
--- a/arch/x86/kernel/kvm.c
+++ b/arch/x86/kernel/kvm.c
@@ -238,12 +238,12 @@ EXPORT_SYMBOL_GPL(kvm_read_and_reset_apf_flags);
 noinstr bool __kvm_handle_async_pf(struct pt_regs *regs, u32 token)
 {
 	u32 flags = kvm_read_and_reset_apf_flags();
-	irqentry_state_t state;
+	irqentry_state_t irq_state;
 
 	if (!flags)
 		return false;
 
-	state = irqentry_enter(regs);
+	irqentry_enter(regs, &irq_state);
 	instrumentation_begin();
 
 	/*
@@ -264,7 +264,7 @@ noinstr bool __kvm_handle_async_pf(struct pt_regs *regs, u32 token)
 	}
 
 	instrumentation_end();
-	irqentry_exit(regs, state);
+	irqentry_exit(regs, &irq_state);
 	return true;
 }
 
diff --git a/arch/x86/kernel/nmi.c b/arch/x86/kernel/nmi.c
index bf250a339655..1fd7780e99dd 100644
--- a/arch/x86/kernel/nmi.c
+++ b/arch/x86/kernel/nmi.c
@@ -502,14 +502,14 @@ DEFINE_IDTENTRY_RAW(exc_nmi)
 
 	this_cpu_write(nmi_dr7, local_db_save());
 
-	irq_state = irqentry_nmi_enter(regs);
+	irqentry_nmi_enter(regs, &irq_state);
 
 	inc_irq_stat(__nmi_count);
 
 	if (!ignore_nmis)
 		default_do_nmi(regs);
 
-	irqentry_nmi_exit(regs, irq_state);
+	irqentry_nmi_exit(regs, &irq_state);
 
 	local_db_restore(this_cpu_read(nmi_dr7));
 
diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
index e1b78829d909..8481cc373794 100644
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -245,7 +245,7 @@ static noinstr bool handle_bug(struct pt_regs *regs)
 
 DEFINE_IDTENTRY_RAW(exc_invalid_op)
 {
-	irqentry_state_t state;
+	irqentry_state_t irq_state;
 
 	/*
 	 * We use UD2 as a short encoding for 'CALL __WARN', as such
@@ -255,11 +255,11 @@ DEFINE_IDTENTRY_RAW(exc_invalid_op)
 	if (!user_mode(regs) && handle_bug(regs))
 		return;
 
-	state = irqentry_enter(regs);
+	irqentry_enter(regs, &irq_state);
 	instrumentation_begin();
 	handle_invalid_op(regs);
 	instrumentation_end();
-	irqentry_exit(regs, state);
+	irqentry_exit(regs, &irq_state);
 }
 
 DEFINE_IDTENTRY(exc_coproc_segment_overrun)
@@ -343,6 +343,7 @@ __visible void __noreturn handle_stack_overflow(const char *message,
  */
 DEFINE_IDTENTRY_DF(exc_double_fault)
 {
+	irqentry_state_t irq_state;
 	static const char str[] = "double fault";
 	struct task_struct *tsk = current;
 
@@ -405,7 +406,7 @@ DEFINE_IDTENTRY_DF(exc_double_fault)
 	}
 #endif
 
-	irqentry_nmi_enter(regs);
+	irqentry_nmi_enter(regs, &irq_state);
 	instrumentation_begin();
 	notify_die(DIE_TRAP, str, regs, error_code, X86_TRAP_DF, SIGSEGV);
 
@@ -651,13 +652,15 @@ DEFINE_IDTENTRY_RAW(exc_int3)
 		instrumentation_end();
 		irqentry_exit_to_user_mode(regs);
 	} else {
-		irqentry_state_t irq_state = irqentry_nmi_enter(regs);
+		irqentry_state_t irq_state;
+
+		irqentry_nmi_enter(regs, &irq_state);
 
 		instrumentation_begin();
 		if (!do_int3(regs))
 			die("int3", regs, 0);
 		instrumentation_end();
-		irqentry_nmi_exit(regs, irq_state);
+		irqentry_nmi_exit(regs, &irq_state);
 	}
 }
 
@@ -852,7 +855,9 @@ static __always_inline void exc_debug_kernel(struct pt_regs *regs,
 	 * includes the entry stack is excluded for everything.
 	 */
 	unsigned long dr7 = local_db_save();
-	irqentry_state_t irq_state = irqentry_nmi_enter(regs);
+	irqentry_state_t irq_state;
+
+	irqentry_nmi_enter(regs, &irq_state);
 	instrumentation_begin();
 
 	/*
@@ -909,7 +914,7 @@ static __always_inline void exc_debug_kernel(struct pt_regs *regs,
 		regs->flags &= ~X86_EFLAGS_TF;
 out:
 	instrumentation_end();
-	irqentry_nmi_exit(regs, irq_state);
+	irqentry_nmi_exit(regs, &irq_state);
 
 	local_db_restore(dr7);
 }
diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
index 82bf37a5c9ec..8d20c4c13abf 100644
--- a/arch/x86/mm/fault.c
+++ b/arch/x86/mm/fault.c
@@ -1441,7 +1441,7 @@ handle_page_fault(struct pt_regs *regs, unsigned long error_code,
 DEFINE_IDTENTRY_RAW_ERRORCODE(exc_page_fault)
 {
 	unsigned long address = read_cr2();
-	irqentry_state_t state;
+	irqentry_state_t irq_state;
 
 	prefetchw(&current->mm->mmap_lock);
 
@@ -1479,11 +1479,11 @@ DEFINE_IDTENTRY_RAW_ERRORCODE(exc_page_fault)
 	 * code reenabled RCU to avoid subsequent wreckage which helps
 	 * debugability.
 	 */
-	state = irqentry_enter(regs);
+	irqentry_enter(regs, &irq_state);
 
 	instrumentation_begin();
 	handle_page_fault(regs, error_code, address);
 	instrumentation_end();
 
-	irqentry_exit(regs, state);
+	irqentry_exit(regs, &irq_state);
 }
diff --git a/include/linux/entry-common.h b/include/linux/entry-common.h
index 49b26b216e4e..dd473137e728 100644
--- a/include/linux/entry-common.h
+++ b/include/linux/entry-common.h
@@ -358,6 +358,8 @@ typedef struct irqentry_state {
 /**
  * irqentry_enter - Handle state tracking on ordinary interrupt entries
  * @regs:	Pointer to pt_regs of interrupted context
+ * @irq_state:	Pointer to an opaque object to store state information; to be
+ *              passed back to irqentry_exit()
  *
  * Invokes:
  *  - lockdep irqflag state tracking as low level ASM entry disabled
@@ -383,10 +385,8 @@ typedef struct irqentry_state {
  * For user mode entries irqentry_enter_from_user_mode() is 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()
  */
-irqentry_state_t noinstr irqentry_enter(struct pt_regs *regs);
+void noinstr irqentry_enter(struct pt_regs *regs, irqentry_state_t *irq_state);
 
 /**
  * irqentry_exit_cond_resched - Conditionally reschedule on return from interrupt
@@ -398,7 +398,7 @@ void irqentry_exit_cond_resched(void);
 /**
  * irqentry_exit - Handle return from exception that used irqentry_enter()
  * @regs:	Pointer to pt_regs (exception entry regs)
- * @state:	Return value from matching call to irqentry_enter()
+ * @irq_state:	Pointer to state information passed to irqentry_enter()
  *
  * Depending on the return target (kernel/user) this runs the necessary
  * preemption and work checks if possible and required and returns to
@@ -409,25 +409,27 @@ void irqentry_exit_cond_resched(void);
  *
  * Counterpart to irqentry_enter().
  */
-void noinstr irqentry_exit(struct pt_regs *regs, irqentry_state_t state);
+void noinstr irqentry_exit(struct pt_regs *regs, irqentry_state_t *irq_state);
 
 /**
  * irqentry_nmi_enter - Handle NMI entry
  * @regs:	Pointer to currents pt_regs
+ * @irq_state:	Pointer to an opaque object to store state information; to be
+ *              passed back to irqentry_nmi_exit()
  *
  * Similar to irqentry_enter() but taking care of the NMI constraints.
  */
-irqentry_state_t noinstr irqentry_nmi_enter(struct pt_regs *regs);
+void noinstr irqentry_nmi_enter(struct pt_regs *regs, irqentry_state_t *irq_state);
 
 /**
  * irqentry_nmi_exit - Handle return from NMI handling
  * @regs:	Pointer to pt_regs (NMI entry regs)
- * @irq_state:	Return value from matching call to irqentry_nmi_enter()
+ * @irq_state:	Pointer to state information passed to irqentry_nmi_enter()
  *
  * Last action before returning to the low level assembly code.
  *
  * Counterpart to irqentry_nmi_enter().
  */
-void noinstr irqentry_nmi_exit(struct pt_regs *regs, irqentry_state_t irq_state);
+void noinstr irqentry_nmi_exit(struct pt_regs *regs, irqentry_state_t *irq_state);
 
 #endif
diff --git a/kernel/entry/common.c b/kernel/entry/common.c
index 91e8fd50adf4..c5d586d5cf5b 100644
--- a/kernel/entry/common.c
+++ b/kernel/entry/common.c
@@ -290,15 +290,13 @@ noinstr void irqentry_exit_to_user_mode(struct pt_regs *regs)
 	exit_to_user_mode();
 }
 
-noinstr irqentry_state_t irqentry_enter(struct pt_regs *regs)
+noinstr void irqentry_enter(struct pt_regs *regs, irqentry_state_t *irq_state)
 {
-	irqentry_state_t ret = {
-		.exit_rcu = false,
-	};
+	irq_state->exit_rcu = false;
 
 	if (user_mode(regs)) {
 		irqentry_enter_from_user_mode(regs);
-		return ret;
+		return;
 	}
 
 	/*
@@ -336,8 +334,8 @@ noinstr irqentry_state_t irqentry_enter(struct pt_regs *regs)
 		trace_hardirqs_off_finish();
 		instrumentation_end();
 
-		ret.exit_rcu = true;
-		return ret;
+		irq_state->exit_rcu = true;
+		return;
 	}
 
 	/*
@@ -351,8 +349,6 @@ noinstr irqentry_state_t irqentry_enter(struct pt_regs *regs)
 	rcu_irq_enter_check_tick();
 	trace_hardirqs_off_finish();
 	instrumentation_end();
-
-	return ret;
 }
 
 void irqentry_exit_cond_resched(void)
@@ -367,7 +363,7 @@ void irqentry_exit_cond_resched(void)
 	}
 }
 
-noinstr void irqentry_exit(struct pt_regs *regs, irqentry_state_t state)
+noinstr void irqentry_exit(struct pt_regs *regs, irqentry_state_t *irq_state)
 {
 	lockdep_assert_irqs_disabled();
 
@@ -380,7 +376,7 @@ noinstr void irqentry_exit(struct pt_regs *regs, irqentry_state_t state)
 		 * carefully and needs the same ordering of lockdep/tracing
 		 * and RCU as the return to user mode path.
 		 */
-		if (state.exit_rcu) {
+		if (irq_state->exit_rcu) {
 			instrumentation_begin();
 			/* Tell the tracer that IRET will enable interrupts */
 			trace_hardirqs_on_prepare();
@@ -402,16 +398,14 @@ noinstr void irqentry_exit(struct pt_regs *regs, irqentry_state_t state)
 		 * IRQ flags state is correct already. Just tell RCU if it
 		 * was not watching on entry.
 		 */
-		if (state.exit_rcu)
+		if (irq_state->exit_rcu)
 			rcu_irq_exit();
 	}
 }
 
-irqentry_state_t noinstr irqentry_nmi_enter(struct pt_regs *regs)
+void noinstr irqentry_nmi_enter(struct pt_regs *regs, irqentry_state_t *irq_state)
 {
-	irqentry_state_t irq_state;
-
-	irq_state.lockdep = lockdep_hardirqs_enabled();
+	irq_state->lockdep = lockdep_hardirqs_enabled();
 
 	__nmi_enter();
 	lockdep_hardirqs_off(CALLER_ADDR0);
@@ -422,15 +416,13 @@ irqentry_state_t noinstr irqentry_nmi_enter(struct pt_regs *regs)
 	trace_hardirqs_off_finish();
 	ftrace_nmi_enter();
 	instrumentation_end();
-
-	return irq_state;
 }
 
-void noinstr irqentry_nmi_exit(struct pt_regs *regs, irqentry_state_t irq_state)
+void noinstr irqentry_nmi_exit(struct pt_regs *regs, irqentry_state_t *irq_state)
 {
 	instrumentation_begin();
 	ftrace_nmi_exit();
-	if (irq_state.lockdep) {
+	if (irq_state->lockdep) {
 		trace_hardirqs_on_prepare();
 		lockdep_hardirqs_on_prepare(CALLER_ADDR0);
 	}
@@ -438,7 +430,7 @@ void noinstr irqentry_nmi_exit(struct pt_regs *regs, irqentry_state_t irq_state)
 
 	rcu_nmi_exit();
 	lockdep_hardirq_exit();
-	if (irq_state.lockdep)
+	if (irq_state->lockdep)
 		lockdep_hardirqs_on(CALLER_ADDR0);
 	__nmi_exit();
 }
-- 
2.28.0.rc0.12.gb6a658bd00c9