linux-kernel - [PATCH 4/5] arm64: Implement IRQ exit preemption static call for dynamic preemption

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Message-Id: <20211220140142.922323-5-frederic@kernel.org>
Date:   Mon, 20 Dec 2021 15:01:41 +0100
From:   Frederic Weisbecker <frederic@...nel.org>
To:     LKML <linux-kernel@...r.kernel.org>
Cc:     Frederic Weisbecker <frederic@...nel.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Ard Biesheuvel <ardb@...nel.org>,
        Kees Cook <keescook@...omium.org>,
        James Morse <james.morse@....com>,
        David Laight <David.Laight@...LAB.COM>,
        Sami Tolvanen <samitolvanen@...gle.com>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Andy Lutomirski <luto@...nel.org>,
        Quentin Perret <qperret@...gle.com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Mark Rutland <mark.rutland@....com>
Subject: [PATCH 4/5] arm64: Implement IRQ exit preemption static call for dynamic preemption

arm64 doesn't support generic entry yet, so the architecture's own IRQ
exit preemption path needs to be exposed through the relevant static
call.

Signed-off-by: Frederic Weisbecker <frederic@...nel.org>
Cc: Mark Rutland <mark.rutland@....com>
Cc: Quentin Perret <qperret@...gle.com>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Catalin Marinas <catalin.marinas@....com>
Cc: James Morse <james.morse@....com>
Cc: Will Deacon <will@...nel.org>
Cc: Ard Biesheuvel <ardb@...nel.org>
Cc: David Laight <David.Laight@...LAB.COM>
Cc: Kees Cook <keescook@...omium.org>
Cc: Sami Tolvanen <samitolvanen@...gle.com>
Cc: Andy Lutomirski <luto@...nel.org>
Cc: Josh Poimboeuf <jpoimboe@...hat.com>
Cc: Steven Rostedt <rostedt@...dmis.org>
---
 arch/arm64/include/asm/preempt.h |  7 +++++++
 arch/arm64/kernel/entry-common.c | 15 ++++++++++++---
 2 files changed, 19 insertions(+), 3 deletions(-)

diff --git a/arch/arm64/include/asm/preempt.h b/arch/arm64/include/asm/preempt.h
index e83f0982b99c..4fbbe644532f 100644
--- a/arch/arm64/include/asm/preempt.h
+++ b/arch/arm64/include/asm/preempt.h
@@ -3,6 +3,7 @@
 #define __ASM_PREEMPT_H
 
 #include <linux/thread_info.h>
+#include <linux/static_call_types.h>
 
 #define PREEMPT_NEED_RESCHED	BIT(32)
 #define PREEMPT_ENABLED	(PREEMPT_NEED_RESCHED)
@@ -86,4 +87,10 @@ void preempt_schedule_notrace(void);
 #define __preempt_schedule_notrace() preempt_schedule_notrace()
 #endif /* CONFIG_PREEMPTION */
 
+#ifdef CONFIG_PREEMPT_DYNAMIC
+void arm64_preempt_schedule_irq(void);
+#define __irqentry_exit_cond_resched_func arm64_preempt_schedule_irq
+DECLARE_STATIC_CALL(irqentry_exit_cond_resched, __irqentry_exit_cond_resched_func);
+#endif /* CONFIG_PREEMPT_DYNAMIC */
+
 #endif /* __ASM_PREEMPT_H */
diff --git a/arch/arm64/kernel/entry-common.c b/arch/arm64/kernel/entry-common.c
index f7408edf8571..b4fe707885d9 100644
--- a/arch/arm64/kernel/entry-common.c
+++ b/arch/arm64/kernel/entry-common.c
@@ -12,6 +12,7 @@
 #include <linux/sched.h>
 #include <linux/sched/debug.h>
 #include <linux/thread_info.h>
+#include <linux/static_call.h>
 
 #include <asm/cpufeature.h>
 #include <asm/daifflags.h>
@@ -220,7 +221,7 @@ static void noinstr arm64_exit_el1_dbg(struct pt_regs *regs)
 		lockdep_hardirqs_on(CALLER_ADDR0);
 }
 
-static void __sched arm64_preempt_schedule_irq(void)
+void __sched arm64_preempt_schedule_irq(void)
 {
 	lockdep_assert_irqs_disabled();
 
@@ -244,6 +245,9 @@ static void __sched arm64_preempt_schedule_irq(void)
 	if (system_capabilities_finalized())
 		preempt_schedule_irq();
 }
+#ifdef CONFIG_PREEMPT_DYNAMIC
+DEFINE_STATIC_CALL(irqentry_exit_cond_resched, arm64_preempt_schedule_irq);
+#endif
 
 static void do_interrupt_handler(struct pt_regs *regs,
 				 void (*handler)(struct pt_regs *))
@@ -444,8 +448,13 @@ static __always_inline void __el1_irq(struct pt_regs *regs,
 	 * preempt_count().
 	 */
 	if (IS_ENABLED(CONFIG_PREEMPTION) &&
-	    READ_ONCE(current_thread_info()->preempt_count) == 0)
-		arm64_preempt_schedule_irq();
+	    READ_ONCE(current_thread_info()->preempt_count) == 0) {
+#ifdef CONFIG_PREEMPT_DYNAMIC
+			static_call(irqentry_exit_cond_resched)();
+#else
+			arm64_preempt_schedule_irq();
+#endif
+	}
 
 	exit_to_kernel_mode(regs);
 }
-- 
2.25.1