linux-kernel - [patch V4 part 5 03/31] x86/entry/64: Move softirq stack switch to C

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Date:   Tue, 05 May 2020 15:53:44 +0200
From:   Thomas Gleixner <tglx@...utronix.de>
To:     LKML <linux-kernel@...r.kernel.org>
Cc:     x86@...nel.org, "Paul E. McKenney" <paulmck@...nel.org>,
        Andy Lutomirski <luto@...nel.org>,
        Alexandre Chartre <alexandre.chartre@...cle.com>,
        Frederic Weisbecker <frederic@...nel.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Petr Mladek <pmladek@...e.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Joel Fernandes <joel@...lfernandes.org>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Juergen Gross <jgross@...e.com>,
        Brian Gerst <brgerst@...il.com>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Will Deacon <will@...nel.org>
Subject: [patch V4 part 5 03/31] x86/entry/64: Move softirq stack switch to C

Use the new C code helpers to move do_softirq_own_stack() out of ASM
code. Mark the switching function noinstr as this is really not a good
place for being instrumented.

Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
---
 arch/x86/entry/entry_64.S |   13 -------------
 arch/x86/kernel/irq_64.c  |   12 ++++++++++++
 2 files changed, 12 insertions(+), 13 deletions(-)

--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -1107,19 +1107,6 @@ SYM_CODE_START_LOCAL_NOALIGN(.Lbad_gs)
 SYM_CODE_END(.Lbad_gs)
 	.previous
 
-/* Call softirq on interrupt stack. Interrupts are off. */
-.pushsection .text, "ax"
-SYM_FUNC_START(do_softirq_own_stack)
-	pushq	%rbp
-	mov	%rsp, %rbp
-	ENTER_IRQ_STACK regs=0 old_rsp=%r11
-	call	__do_softirq
-	LEAVE_IRQ_STACK regs=0
-	leaveq
-	ret
-SYM_FUNC_END(do_softirq_own_stack)
-.popsection
-
 #ifdef CONFIG_XEN_PV
 /*
  * A note on the "critical region" in our callback handler.
--- a/arch/x86/kernel/irq_64.c
+++ b/arch/x86/kernel/irq_64.c
@@ -20,6 +20,7 @@
 #include <linux/sched/task_stack.h>
 
 #include <asm/cpu_entry_area.h>
+#include <asm/irq_stack.h>
 #include <asm/io_apic.h>
 #include <asm/apic.h>
 
@@ -70,3 +71,14 @@ int irq_init_percpu_irqstack(unsigned in
 		return 0;
 	return map_irq_stack(cpu);
 }
+
+noinstr void do_softirq_own_stack(void)
+{
+	if (irqstack_active()) {
+		instr_begin();
+		__do_softirq();
+		instr_end();
+	} else {
+		RUN_ON_IRQSTACK(__do_softirq);
+	}
+}