[PATCH V2 06/10] x86/entry: Move nmi entry/exit into common code

ira.weiny
2020-11-02T20:53:44Z

From: Thomas Gleixner <tglx@linutronix.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@linutronix.de>
Signed-off-by: Ira Weiny <ira.weiny@intel.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