[PATCH V3 05/10] x86/entry: Pass irqentry_state_t by reference

ira.weiny
2020-11-06T23:30:30Z

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
propose to add information to this struct, for example the PKRS
register/thread state.

Adding information to irqentry_state_t makes passing by value less
efficient. Therefore, change the entry/exit calls to pass irq_state by
reference.

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 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Missed some 'return' comments which are no longer valid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 66938121c4b1..1193a70bcf1b 100644
--- a/include/linux/entry-common.h
+++ b/include/linux/entry-common.h
@@ -372,6 +372,8 @@ 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
@@ -397,10 +399,8 @@ 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
@@ -412,7 +412,7 @@ 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
@@ -423,25 +423,27 @@ 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 assmebly 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 fa17baadf63e..5ed9d45fb41b 100644
--- a/kernel/entry/common.c
+++ b/kernel/entry/common.c
@@ -289,15 +289,13 @@ 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;
}

/*
@@ -335,8 +333,8 @@ 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;
}

/*
@@ -350,8 +348,6 @@ 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)
@@ -366,7 +362,7 @@ 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();

@@ -379,7 +375,7 @@ 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();
@@ -401,16 +397,14 @@ 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);
@@ -421,15 +415,13 @@ 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);
}
@@ -437,7 +429,7 @@ 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