Date:   Mon,  2 Nov 2020 12:53:16 -0800
From:   ira.weiny@...el.com
To:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Andy Lutomirski <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>
Cc:     Ira Weiny <ira.weiny@...el.com>, x86@...nel.org,
        Dan Williams <dan.j.williams@...el.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Fenghua Yu <fenghua.yu@...el.com>, linux-doc@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-nvdimm@...ts.01.org,
        linux-mm@...ck.org, linux-kselftest@...r.kernel.org
Subject: [PATCH V2 06/10] x86/entry: Move nmi entry/exit into common code

From: Thomas Gleixner <tglx@...utronix.de>

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@...utronix.de>
Signed-off-by: Ira Weiny <ira.weiny@...el.com>

---
Changes from V1
	Update commit message
	Add kernel doc for struct irqentry_state_t
		With Thomas' help
---
 arch/x86/entry/common.c         | 34 ----------------------------
 arch/x86/include/asm/idtentry.h |  3 ---
 arch/x86/kernel/cpu/mce/core.c  |  6 ++---
 arch/x86/kernel/nmi.c           |  6 ++---
 arch/x86/kernel/traps.c         | 13 ++++++-----
 include/linux/entry-common.h    | 39 ++++++++++++++++++++++++++++++++-
 kernel/entry/common.c           | 36 ++++++++++++++++++++++++++++++
 7 files changed, 87 insertions(+), 50 deletions(-)

diff --git a/arch/x86/entry/common.c b/arch/x86/entry/common.c
index 870efeec8bda..18d8f17f755c 100644
--- a/arch/x86/entry/common.c
+++ b/arch/x86/entry/common.c
@@ -209,40 +209,6 @@ SYSCALL_DEFINE0(ni_syscall)
 	return -ENOSYS;
 }
 
-noinstr bool idtentry_enter_nmi(struct pt_regs *regs)
-{
-	bool irq_state = lockdep_hardirqs_enabled();
-
-	__nmi_enter();
-	lockdep_hardirqs_off(CALLER_ADDR0);
-	lockdep_hardirq_enter();
-	rcu_nmi_enter();
-
-	instrumentation_begin();
-	trace_hardirqs_off_finish();
-	ftrace_nmi_enter();
-	instrumentation_end();
-
-	return irq_state;
-}
-
-noinstr void idtentry_exit_nmi(struct pt_regs *regs, bool restore)
-{
-	instrumentation_begin();
-	ftrace_nmi_exit();
-	if (restore) {
-		trace_hardirqs_on_prepare();
-		lockdep_hardirqs_on_prepare(CALLER_ADDR0);
-	}
-	instrumentation_end();
-
-	rcu_nmi_exit();
-	lockdep_hardirq_exit();
-	if (restore)
-		lockdep_hardirqs_on(CALLER_ADDR0);
-	__nmi_exit();
-}
-
 #ifdef CONFIG_XEN_PV
 #ifndef CONFIG_PREEMPTION
 /*
diff --git a/arch/x86/include/asm/idtentry.h b/arch/x86/include/asm/idtentry.h
index b2442eb0ac2f..247a60a47331 100644
--- a/arch/x86/include/asm/idtentry.h
+++ b/arch/x86/include/asm/idtentry.h
@@ -11,9 +11,6 @@
 
 #include <asm/irq_stack.h>
 
-bool idtentry_enter_nmi(struct pt_regs *regs);
-void idtentry_exit_nmi(struct pt_regs *regs, bool irq_state);
-
 /**
  * DECLARE_IDTENTRY - Declare functions for simple IDT entry points
  *		      No error code pushed by hardware
diff --git a/arch/x86/kernel/cpu/mce/core.c b/arch/x86/kernel/cpu/mce/core.c
index 51bf910b1e9d..403561a89c28 100644
--- a/arch/x86/kernel/cpu/mce/core.c
+++ b/arch/x86/kernel/cpu/mce/core.c
@@ -1981,7 +1981,7 @@ void (*machine_check_vector)(struct pt_regs *) = unexpected_machine_check;
 
 static __always_inline void exc_machine_check_kernel(struct pt_regs *regs)
 {
-	bool irq_state;
+	irqentry_state_t irq_state;
 
 	WARN_ON_ONCE(user_mode(regs));
 
@@ -1993,7 +1993,7 @@ static __always_inline void exc_machine_check_kernel(struct pt_regs *regs)
 	    mce_check_crashing_cpu())
 		return;
 
-	irq_state = idtentry_enter_nmi(regs);
+	irq_state = irqentry_nmi_enter(regs);
 	/*
 	 * The call targets are marked noinstr, but objtool can't figure
 	 * that out because it's an indirect call. Annotate it.
@@ -2004,7 +2004,7 @@ static __always_inline void exc_machine_check_kernel(struct pt_regs *regs)
 	if (regs->flags & X86_EFLAGS_IF)
 		trace_hardirqs_on_prepare();
 	instrumentation_end();
-	idtentry_exit_nmi(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/nmi.c b/arch/x86/kernel/nmi.c
index 4bc77aaf1303..bf250a339655 100644
--- a/arch/x86/kernel/nmi.c
+++ b/arch/x86/kernel/nmi.c
@@ -475,7 +475,7 @@ static DEFINE_PER_CPU(unsigned long, nmi_dr7);
 
 DEFINE_IDTENTRY_RAW(exc_nmi)
 {
-	bool irq_state;
+	irqentry_state_t irq_state;
 
 	/*
 	 * Re-enable NMIs right here when running as an SEV-ES guest. This might
@@ -502,14 +502,14 @@ DEFINE_IDTENTRY_RAW(exc_nmi)
 
 	this_cpu_write(nmi_dr7, local_db_save());
 
-	irq_state = idtentry_enter_nmi(regs);
+	irq_state = irqentry_nmi_enter(regs);
 
 	inc_irq_stat(__nmi_count);
 
 	if (!ignore_nmis)
 		default_do_nmi(regs);
 
-	idtentry_exit_nmi(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 e19df6cde35d..e1b78829d909 100644
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -405,7 +405,7 @@ DEFINE_IDTENTRY_DF(exc_double_fault)
 	}
 #endif
 
-	idtentry_enter_nmi(regs);
+	irqentry_nmi_enter(regs);
 	instrumentation_begin();
 	notify_die(DIE_TRAP, str, regs, error_code, X86_TRAP_DF, SIGSEGV);
 
@@ -651,12 +651,13 @@ DEFINE_IDTENTRY_RAW(exc_int3)
 		instrumentation_end();
 		irqentry_exit_to_user_mode(regs);
 	} else {
-		bool irq_state = idtentry_enter_nmi(regs);
+		irqentry_state_t irq_state = irqentry_nmi_enter(regs);
+
 		instrumentation_begin();
 		if (!do_int3(regs))
 			die("int3", regs, 0);
 		instrumentation_end();
-		idtentry_exit_nmi(regs, irq_state);
+		irqentry_nmi_exit(regs, irq_state);
 	}
 }
 
@@ -851,7 +852,7 @@ 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();
-	bool irq_state = idtentry_enter_nmi(regs);
+	irqentry_state_t irq_state = irqentry_nmi_enter(regs);
 	instrumentation_begin();
 
 	/*
@@ -908,7 +909,7 @@ static __always_inline void exc_debug_kernel(struct pt_regs *regs,
 		regs->flags &= ~X86_EFLAGS_TF;
 out:
 	instrumentation_end();
-	idtentry_exit_nmi(regs, irq_state);
+	irqentry_nmi_exit(regs, irq_state);
 
 	local_db_restore(dr7);
 }
@@ -926,7 +927,7 @@ static __always_inline void exc_debug_user(struct pt_regs *regs,
 
 	/*
 	 * NB: We can't easily clear DR7 here because
-	 * idtentry_exit_to_usermode() can invoke ptrace, schedule, access
+	 * irqentry_exit_to_usermode() can invoke ptrace, schedule, access
 	 * user memory, etc.  This means that a recursive #DB is possible.  If
 	 * this happens, that #DB will hit exc_debug_kernel() and clear DR7.
 	 * Since we're not on the IST stack right now, everything will be
diff --git a/include/linux/entry-common.h b/include/linux/entry-common.h
index 474f29638d2c..7dff07713a07 100644
--- a/include/linux/entry-common.h
+++ b/include/linux/entry-common.h
@@ -341,8 +341,26 @@ 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
 
@@ -402,4 +420,23 @@ 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
diff --git a/kernel/entry/common.c b/kernel/entry/common.c
index acb6bec04dc7..372f14cc347f 100644
--- a/kernel/entry/common.c
+++ b/kernel/entry/common.c
@@ -397,3 +397,39 @@ noinstr void irqentry_exit(struct pt_regs *regs, irqentry_state_t state)
 			rcu_irq_exit();
 	}
 }
+
+irqentry_state_t noinstr irqentry_nmi_enter(struct pt_regs *regs)
+{
+	irqentry_state_t irq_state;
+
+	irq_state.lockdep = lockdep_hardirqs_enabled();
+
+	__nmi_enter();
+	lockdep_hardirqs_off(CALLER_ADDR0);
+	lockdep_hardirq_enter();
+	rcu_nmi_enter();
+
+	instrumentation_begin();
+	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)
+{
+	instrumentation_begin();
+	ftrace_nmi_exit();
+	if (irq_state.lockdep) {
+		trace_hardirqs_on_prepare();
+		lockdep_hardirqs_on_prepare(CALLER_ADDR0);
+	}
+	instrumentation_end();
+
+	rcu_nmi_exit();
+	lockdep_hardirq_exit();
+	if (irq_state.lockdep)
+		lockdep_hardirqs_on(CALLER_ADDR0);
+	__nmi_exit();
+}
-- 
2.28.0.rc0.12.gb6a658bd00c9

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