[RFC PATCH 1/5] entry: Pass pt_regs to irqentry_exit_cond_resched()

From: ira.weiny@intel.com
To: Rik van Riel <riel@surriel.com>, Borislav Petkov <bp@alien8.de>,
	Dave Hansen <dave.hansen@intel.com>
Cc: Ira Weiny <ira.weiny@intel.com>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	x86@kernel.org, linux-kernel@vger.kernel.org, kernel-team@fb.com
Subject: [RFC PATCH 1/5] entry: Pass pt_regs to irqentry_exit_cond_resched()
Date: Fri,  5 Aug 2022 10:30:05 -0700	[thread overview]
Message-ID: <20220805173009.3128098-2-ira.weiny@intel.com> (raw)
In-Reply-To: <20220805173009.3128098-1-ira.weiny@intel.com>

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

Auxiliary pt_regs space needs to be manipulated by the generic
entry/exit code.

Ideally irqentry_exit() would take care of handling any auxiliary
pt_regs on exit.  Unfortunately, irqentry_exit() is not the only exit
from exception path.  The call to irqentry_exit_cond_resched() from
xen_pv_evtchn_do_upcall() bypasses irqentry_exit().

Make irqentry_exit_cond_resched() symmetrical with irqentry_enter() by
passing pt_regs to it.  This makes irqentry_exit_cond_resched() capable
of handling auxiliary pt_regs in future patches.

Cc: Rik van Riel <riel@surriel.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Borislav Petkov <bp@alien8.de>
Signed-off-by: Ira Weiny <ira.weiny@intel.com>

---
Forward ported from PKS series:
	https://lore.kernel.org/lkml/20220419170649.1022246-19-ira.weiny@intel.com/
---
 arch/arm64/include/asm/preempt.h |  2 +-
 arch/arm64/kernel/entry-common.c |  4 ++--
 arch/x86/entry/common.c          |  2 +-
 include/linux/entry-common.h     | 17 ++++++++------
 kernel/entry/common.c            | 13 +++++++----
 kernel/sched/core.c              | 40 ++++++++++++++++----------------
 6 files changed, 43 insertions(+), 35 deletions(-)

diff --git a/arch/arm64/include/asm/preempt.h b/arch/arm64/include/asm/preempt.h
index 0159b625cc7f..bd185a214096 100644
--- a/arch/arm64/include/asm/preempt.h
+++ b/arch/arm64/include/asm/preempt.h
@@ -87,7 +87,7 @@ void preempt_schedule_notrace(void);
 
 #ifdef CONFIG_PREEMPT_DYNAMIC
 
-DECLARE_STATIC_KEY_TRUE(sk_dynamic_irqentry_exit_cond_resched);
+DECLARE_STATIC_KEY_TRUE(sk_dynamic_irqentry_exit_cond_resched_internal);
 void dynamic_preempt_schedule(void);
 #define __preempt_schedule()		dynamic_preempt_schedule()
 void dynamic_preempt_schedule_notrace(void);
diff --git a/arch/arm64/kernel/entry-common.c b/arch/arm64/kernel/entry-common.c
index c75ca36b4a49..a1cc8795b729 100644
--- a/arch/arm64/kernel/entry-common.c
+++ b/arch/arm64/kernel/entry-common.c
@@ -224,9 +224,9 @@ static void noinstr arm64_exit_el1_dbg(struct pt_regs *regs)
 }
 
 #ifdef CONFIG_PREEMPT_DYNAMIC
-DEFINE_STATIC_KEY_TRUE(sk_dynamic_irqentry_exit_cond_resched);
+DEFINE_STATIC_KEY_TRUE(sk_dynamic_irqentry_exit_cond_resched_internal);
 #define need_irq_preemption() \
-	(static_branch_unlikely(&sk_dynamic_irqentry_exit_cond_resched))
+	(static_branch_unlikely(&sk_dynamic_irqentry_exit_cond_resched_internal))
 #else
 #define need_irq_preemption()	(IS_ENABLED(CONFIG_PREEMPTION))
 #endif
diff --git a/arch/x86/entry/common.c b/arch/x86/entry/common.c
index 6c2826417b33..f1ba770d035d 100644
--- a/arch/x86/entry/common.c
+++ b/arch/x86/entry/common.c
@@ -309,7 +309,7 @@ __visible noinstr void xen_pv_evtchn_do_upcall(struct pt_regs *regs)
 
 	inhcall = get_and_clear_inhcall();
 	if (inhcall && !WARN_ON_ONCE(state.exit_rcu)) {
-		irqentry_exit_cond_resched();
+		irqentry_exit_cond_resched(regs);
 		instrumentation_end();
 		restore_inhcall(inhcall);
 	} else {
diff --git a/include/linux/entry-common.h b/include/linux/entry-common.h
index 84a466b176cf..976cce7cf803 100644
--- a/include/linux/entry-common.h
+++ b/include/linux/entry-common.h
@@ -412,23 +412,26 @@ irqentry_state_t noinstr irqentry_enter(struct pt_regs *regs);
 
 /**
  * irqentry_exit_cond_resched - Conditionally reschedule on return from interrupt
+ * @regs:	Pointer to pt_regs of interrupted context
  *
  * Conditional reschedule with additional sanity checks.
  */
+void irqentry_exit_cond_resched(struct pt_regs *regs);
+
 void raw_irqentry_exit_cond_resched(void);
 #ifdef CONFIG_PREEMPT_DYNAMIC
 #if defined(CONFIG_HAVE_PREEMPT_DYNAMIC_CALL)
-#define irqentry_exit_cond_resched_dynamic_enabled	raw_irqentry_exit_cond_resched
-#define irqentry_exit_cond_resched_dynamic_disabled	NULL
-DECLARE_STATIC_CALL(irqentry_exit_cond_resched, raw_irqentry_exit_cond_resched);
-#define irqentry_exit_cond_resched()	static_call(irqentry_exit_cond_resched)()
+#define irqentry_exit_cond_resched_internal_dynamic_enabled	raw_irqentry_exit_cond_resched
+#define irqentry_exit_cond_resched_internal_dynamic_disabled	NULL
+DECLARE_STATIC_CALL(irqentry_exit_cond_resched_internal, raw_irqentry_exit_cond_resched);
+#define irqentry_exit_cond_resched_internal() static_call(irqentry_exit_cond_resched_internal)()
 #elif defined(CONFIG_HAVE_PREEMPT_DYNAMIC_KEY)
-DECLARE_STATIC_KEY_TRUE(sk_dynamic_irqentry_exit_cond_resched);
+DECLARE_STATIC_KEY_TRUE(sk_dynamic_irqentry_exit_cond_resched_internal);
 void dynamic_irqentry_exit_cond_resched(void);
-#define irqentry_exit_cond_resched()	dynamic_irqentry_exit_cond_resched()
+#define irqentry_exit_cond_resched_internal()	dynamic_irqentry_exit_cond_resched()
 #endif
 #else /* CONFIG_PREEMPT_DYNAMIC */
-#define irqentry_exit_cond_resched()	raw_irqentry_exit_cond_resched()
+#define irqentry_exit_cond_resched_internal()	raw_irqentry_exit_cond_resched()
 #endif /* CONFIG_PREEMPT_DYNAMIC */
 
 /**
diff --git a/kernel/entry/common.c b/kernel/entry/common.c
index 063068a9ea9b..8c0f334c4b75 100644
--- a/kernel/entry/common.c
+++ b/kernel/entry/common.c
@@ -387,18 +387,23 @@ void raw_irqentry_exit_cond_resched(void)
 }
 #ifdef CONFIG_PREEMPT_DYNAMIC
 #if defined(CONFIG_HAVE_PREEMPT_DYNAMIC_CALL)
-DEFINE_STATIC_CALL(irqentry_exit_cond_resched, raw_irqentry_exit_cond_resched);
+DEFINE_STATIC_CALL(irqentry_exit_cond_resched_internal, raw_irqentry_exit_cond_resched);
 #elif defined(CONFIG_HAVE_PREEMPT_DYNAMIC_KEY)
-DEFINE_STATIC_KEY_TRUE(sk_dynamic_irqentry_exit_cond_resched);
+DEFINE_STATIC_KEY_TRUE(sk_dynamic_irqentry_exit_cond_resched_internal);
 void dynamic_irqentry_exit_cond_resched(void)
 {
-	if (!static_branch_unlikely(&sk_dynamic_irqentry_exit_cond_resched))
+	if (!static_branch_unlikely(&sk_dynamic_irqentry_exit_cond_resched_internal))
 		return;
 	raw_irqentry_exit_cond_resched();
 }
 #endif
 #endif
 
+void irqentry_exit_cond_resched(struct pt_regs *regs)
+{
+	irqentry_exit_cond_resched_internal();
+}
+
 noinstr void irqentry_exit(struct pt_regs *regs, irqentry_state_t state)
 {
 	lockdep_assert_irqs_disabled();
@@ -425,7 +430,7 @@ noinstr void irqentry_exit(struct pt_regs *regs, irqentry_state_t state)
 
 		instrumentation_begin();
 		if (IS_ENABLED(CONFIG_PREEMPTION))
-			irqentry_exit_cond_resched();
+			irqentry_exit_cond_resched_internal();
 
 		/* Covers both tracing and lockdep */
 		trace_hardirqs_on();
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 189999007f32..38dd74ba1c86 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -8419,29 +8419,29 @@ EXPORT_SYMBOL(__cond_resched_rwlock_write);
  * SC:might_resched
  * SC:preempt_schedule
  * SC:preempt_schedule_notrace
- * SC:irqentry_exit_cond_resched
+ * SC:irqentry_exit_cond_resched_internal
  *
  *
  * NONE:
- *   cond_resched               <- __cond_resched
- *   might_resched              <- RET0
- *   preempt_schedule           <- NOP
- *   preempt_schedule_notrace   <- NOP
- *   irqentry_exit_cond_resched <- NOP
+ *   cond_resched                        <- __cond_resched
+ *   might_resched                       <- RET0
+ *   preempt_schedule                    <- NOP
+ *   preempt_schedule_notrace            <- NOP
+ *   irqentry_exit_cond_resched_internal <- NOP
  *
  * VOLUNTARY:
- *   cond_resched               <- __cond_resched
- *   might_resched              <- __cond_resched
- *   preempt_schedule           <- NOP
- *   preempt_schedule_notrace   <- NOP
- *   irqentry_exit_cond_resched <- NOP
+ *   cond_resched                        <- __cond_resched
+ *   might_resched                       <- __cond_resched
+ *   preempt_schedule                    <- NOP
+ *   preempt_schedule_notrace            <- NOP
+ *   irqentry_exit_cond_resched_internal <- NOP
  *
  * FULL:
- *   cond_resched               <- RET0
- *   might_resched              <- RET0
- *   preempt_schedule           <- preempt_schedule
- *   preempt_schedule_notrace   <- preempt_schedule_notrace
- *   irqentry_exit_cond_resched <- irqentry_exit_cond_resched
+ *   cond_resched                        <- RET0
+ *   might_resched                       <- RET0
+ *   preempt_schedule                    <- preempt_schedule
+ *   preempt_schedule_notrace            <- preempt_schedule_notrace
+ *   irqentry_exit_cond_resched_internal <- irqentry_exit_cond_resched_internal
  */
 
 enum {
@@ -8487,7 +8487,7 @@ void sched_dynamic_update(int mode)
 	preempt_dynamic_enable(might_resched);
 	preempt_dynamic_enable(preempt_schedule);
 	preempt_dynamic_enable(preempt_schedule_notrace);
-	preempt_dynamic_enable(irqentry_exit_cond_resched);
+	preempt_dynamic_enable(irqentry_exit_cond_resched_internal);
 
 	switch (mode) {
 	case preempt_dynamic_none:
@@ -8495,7 +8495,7 @@ void sched_dynamic_update(int mode)
 		preempt_dynamic_disable(might_resched);
 		preempt_dynamic_disable(preempt_schedule);
 		preempt_dynamic_disable(preempt_schedule_notrace);
-		preempt_dynamic_disable(irqentry_exit_cond_resched);
+		preempt_dynamic_disable(irqentry_exit_cond_resched_internal);
 		pr_info("Dynamic Preempt: none\n");
 		break;
 
@@ -8504,7 +8504,7 @@ void sched_dynamic_update(int mode)
 		preempt_dynamic_enable(might_resched);
 		preempt_dynamic_disable(preempt_schedule);
 		preempt_dynamic_disable(preempt_schedule_notrace);
-		preempt_dynamic_disable(irqentry_exit_cond_resched);
+		preempt_dynamic_disable(irqentry_exit_cond_resched_internal);
 		pr_info("Dynamic Preempt: voluntary\n");
 		break;
 
@@ -8513,7 +8513,7 @@ void sched_dynamic_update(int mode)
 		preempt_dynamic_disable(might_resched);
 		preempt_dynamic_enable(preempt_schedule);
 		preempt_dynamic_enable(preempt_schedule_notrace);
-		preempt_dynamic_enable(irqentry_exit_cond_resched);
+		preempt_dynamic_enable(irqentry_exit_cond_resched_internal);
 		pr_info("Dynamic Preempt: full\n");
 		break;
 	}
-- 
2.35.3

