x86/entry: Move nmi entry/exit into common code

Lockdep state handling on NMI enter and exit is nothing specific to X86. It's
not any different on other architectures. Also the extra state type is not
necessary, irqentry_state_t can carry the necessary information as well.

Move it to common code and extend irqentry_state_t to carry lockdep state.

[ Ira: Make exit_rcu and lockdep a union as they are mutually exclusive
  between the IRQ and NMI exceptions, and add kernel documentation for
  struct irqentry_state_t ]

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ira Weiny <ira.weiny@intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20201102205320.1458656-7-ira.weiny@intel.com

1 files changed, 38 insertions, 1 deletions

diff --git a/include/linux/entry-common.h b/include/linux/entry-common.h
index b9711e813ec2..1a128baf3628 100644
--- a/include/linux/entry-common.h
+++ b/include/linux/entry-common.h
@@ -346,8 +346,26 @@ void irqentry_enter_from_user_mode(struct pt_regs *regs);
 void irqentry_exit_to_user_mode(struct pt_regs *regs);
 
 #ifndef irqentry_state
+/**
+ * struct irqentry_state - Opaque object for exception state storage
+ * @exit_rcu: Used exclusively in the irqentry_*() calls; signals whether the
+ *            exit path has to invoke rcu_irq_exit().
+ * @lockdep: Used exclusively in the irqentry_nmi_*() calls; ensures that
+ *           lockdep state is restored correctly on exit from nmi.
+ *
+ * This opaque object is filled in by the irqentry_*_enter() functions and
+ * must be passed back into the corresponding irqentry_*_exit() functions
+ * when the exception is complete.
+ *
+ * Callers of irqentry_*_[enter|exit]() must consider this structure opaque
+ * and all members private.  Descriptions of the members are provided to aid in
+ * the maintenance of the irqentry_*() functions.
+ */
 typedef struct irqentry_state {
-	bool	exit_rcu;
+	union {
+		bool	exit_rcu;
+		bool	lockdep;
+	};
 } irqentry_state_t;
 #endif
 
@@ -407,4 +425,23 @@ void irqentry_exit_cond_resched(void);
  */
 void noinstr irqentry_exit(struct pt_regs *regs, irqentry_state_t state);
 
+/**
+ * irqentry_nmi_enter - Handle NMI entry
+ * @regs:	Pointer to currents pt_regs
+ *
+ * Similar to irqentry_enter() but taking care of the NMI constraints.
+ */
+irqentry_state_t noinstr irqentry_nmi_enter(struct pt_regs *regs);
+
+/**
+ * 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()
+ *
+ * Last action before returning to the low level assmenbly code.
+ *
+ * Counterpart to irqentry_nmi_enter().
+ */
+void noinstr irqentry_nmi_exit(struct pt_regs *regs, irqentry_state_t irq_state);
+
 #endif