linux-kernel - [PATCH] x86/realmode: remove trampoline

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Date:   Tue, 16 Jul 2019 16:40:24 +0800
From:   Pingfan Liu <kernelfans@...il.com>
To:     x86@...nel.org
Cc:     Pingfan Liu <kernelfans@...il.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        Mukesh Ojha <mojha@...eaurora.org>,
        Matteo Croce <mcroce@...hat.com>,
        Len Brown <len.brown@...el.com>, Pu Wen <puwen@...on.cn>,
        Nicolai Stange <nstange@...e.de>,
        Hui Wang <john.wanghui@...wei.com>,
        linux-kernel@...r.kernel.org
Subject: [PATCH] x86/realmode: remove trampoline_status flag

In current code, there is no reader of trampoline_status. It turns out that
after commit ce4b1b16502b ("x86/smpboot: Initialize secondary CPU only if
master CPU will wait for it"), trampoline_status is not needed any more.

Signed-off-by: Pingfan Liu <kernelfans@...il.com>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Ingo Molnar <mingo@...hat.com>
Cc: Borislav Petkov <bp@...en8.de>
Cc: "H. Peter Anvin" <hpa@...or.com>
Cc: Mukesh Ojha <mojha@...eaurora.org>
Cc: Matteo Croce <mcroce@...hat.com>
Cc: Len Brown <len.brown@...el.com>
Cc: Pu Wen <puwen@...on.cn>
Cc: Nicolai Stange <nstange@...e.de>
Cc: Hui Wang <john.wanghui@...wei.com>
Cc: linux-kernel@...r.kernel.org
---
 arch/x86/include/asm/realmode.h          | 1 -
 arch/x86/kernel/smpboot.c                | 5 -----
 arch/x86/realmode/rm/header.S            | 1 -
 arch/x86/realmode/rm/trampoline_32.S     | 3 ---
 arch/x86/realmode/rm/trampoline_64.S     | 3 ---
 arch/x86/realmode/rm/trampoline_common.S | 4 ----
 6 files changed, 17 deletions(-)

diff --git a/arch/x86/include/asm/realmode.h b/arch/x86/include/asm/realmode.h
index c536823..09ecc32 100644
--- a/arch/x86/include/asm/realmode.h
+++ b/arch/x86/include/asm/realmode.h
@@ -20,7 +20,6 @@ struct real_mode_header {
 	u32	ro_end;
 	/* SMP trampoline */
 	u32	trampoline_start;
-	u32	trampoline_status;
 	u32	trampoline_header;
 #ifdef CONFIG_X86_64
 	u32	trampoline_pgd;
diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index 362dd89..2ef10d9 100644
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -965,8 +965,6 @@ int common_cpu_up(unsigned int cpu, struct task_struct *idle)
 static int do_boot_cpu(int apicid, int cpu, struct task_struct *idle,
 		       int *cpu0_nmi_registered)
 {
-	volatile u32 *trampoline_status =
-		(volatile u32 *) __va(real_mode_header->trampoline_status);
 	/* start_ip had better be page-aligned! */
 	unsigned long start_ip = real_mode_header->trampoline_start;
 
@@ -1058,9 +1056,6 @@ static int do_boot_cpu(int apicid, int cpu, struct task_struct *idle,
 		}
 	}
 
-	/* mark "stuck" area as not stuck */
-	*trampoline_status = 0;
-
 	if (x86_platform.legacy.warm_reset) {
 		/*
 		 * Cleanup possible dangling ends...
diff --git a/arch/x86/realmode/rm/header.S b/arch/x86/realmode/rm/header.S
index 30b0d30..6363761 100644
--- a/arch/x86/realmode/rm/header.S
+++ b/arch/x86/realmode/rm/header.S
@@ -19,7 +19,6 @@ GLOBAL(real_mode_header)
 	.long	pa_ro_end
 	/* SMP trampoline */
 	.long	pa_trampoline_start
-	.long	pa_trampoline_status
 	.long	pa_trampoline_header
 #ifdef CONFIG_X86_64
 	.long	pa_trampoline_pgd;
diff --git a/arch/x86/realmode/rm/trampoline_32.S b/arch/x86/realmode/rm/trampoline_32.S
index 2dd866c..1868b15 100644
--- a/arch/x86/realmode/rm/trampoline_32.S
+++ b/arch/x86/realmode/rm/trampoline_32.S
@@ -41,9 +41,6 @@ ENTRY(trampoline_start)
 
 	movl	tr_start, %eax	# where we need to go
 
-	movl	$0xA5A5A5A5, trampoline_status
-				# write marker for master knows we're running
-
 	/*
 	 * GDT tables in non default location kernel can be beyond 16MB and
 	 * lgdt will not be able to load the address as in real mode default
diff --git a/arch/x86/realmode/rm/trampoline_64.S b/arch/x86/realmode/rm/trampoline_64.S
index 24bb759..aee2b45 100644
--- a/arch/x86/realmode/rm/trampoline_64.S
+++ b/arch/x86/realmode/rm/trampoline_64.S
@@ -49,9 +49,6 @@ ENTRY(trampoline_start)
 	mov	%ax, %es
 	mov	%ax, %ss
 
-	movl	$0xA5A5A5A5, trampoline_status
-	# write marker for master knows we're running
-
 	# Setup stack
 	movl	$rm_stack_end, %esp
 
diff --git a/arch/x86/realmode/rm/trampoline_common.S b/arch/x86/realmode/rm/trampoline_common.S
index 7c70677..8d8208d 100644
--- a/arch/x86/realmode/rm/trampoline_common.S
+++ b/arch/x86/realmode/rm/trampoline_common.S
@@ -2,7 +2,3 @@
 	.section ".rodata","a"
 	.balign	16
 tr_idt: .fill 1, 6, 0
-
-	.bss
-	.balign	4
-GLOBAL(trampoline_status)	.space	4
-- 
2.7.5