linux-kernel - [v4][PATCH 5/8] book3e/kexec/kdump: introduce a kexec kernel flag

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Date:	Mon, 26 Aug 2013 11:00:55 +0800
From:	Tiejun Chen <tiejun.chen@...driver.com>
To:	<benh@...nel.crashing.org>
CC:	<linux-kernel@...r.kernel.org>
Subject: [v4][PATCH 5/8] book3e/kexec/kdump: introduce a kexec kernel flag

We need to introduce a flag to indicate we're already running
a kexec kernel then we can go proper path. For example, We
shouldn't access spin_table from the bootloader to up any secondary
cpu for kexec kernel, and kexec kernel already know how to jump to
generic_secondary_smp_init.

Signed-off-by: Tiejun Chen <tiejun.chen@...driver.com>
---
 arch/powerpc/include/asm/smp.h    |    1 +
 arch/powerpc/kernel/head_64.S     |   10 ++++++++++
 arch/powerpc/kernel/misc_64.S     |    6 ++++++
 arch/powerpc/platforms/85xx/smp.c |   20 +++++++++++++++-----
 4 files changed, 32 insertions(+), 5 deletions(-)

diff --git a/arch/powerpc/include/asm/smp.h b/arch/powerpc/include/asm/smp.h
index 98da78e..92f7e61 100644
--- a/arch/powerpc/include/asm/smp.h
+++ b/arch/powerpc/include/asm/smp.h
@@ -207,6 +207,7 @@ extern void generic_secondary_thread_init(void);
 extern unsigned long __secondary_hold_spinloop;
 extern unsigned long __secondary_hold_acknowledge;
 extern char __secondary_hold;
+extern unsigned long __run_at_kexec;
 
 extern void __early_start(void);
 #endif /* __ASSEMBLY__ */
diff --git a/arch/powerpc/kernel/head_64.S b/arch/powerpc/kernel/head_64.S
index fd42f8a..fa74d20 100644
--- a/arch/powerpc/kernel/head_64.S
+++ b/arch/powerpc/kernel/head_64.S
@@ -89,6 +89,10 @@ __secondary_hold_spinloop:
 __secondary_hold_acknowledge:
 	.llong	0x0
 
+	.globl	__run_at_kexec
+__run_at_kexec:
+	.llong	0x0	/* Flag for the secondary kernel from kexec. */
+
 #ifdef CONFIG_RELOCATABLE
 	/* This flag is set to 1 by a loader if the kernel should run
 	 * at the loaded address instead of the linked address.  This
@@ -426,6 +430,7 @@ _STATIC(__after_prom_start)
 	add	r25,r25,r26
 1:	mr	r3,r25
 	bl	.relocate
+
 #if defined(CONFIG_PPC_BOOK3E)
 	/* In relocatable case we always have to load the address of label 'name'
 	 * to set IVPR. So after .relocate we have to update IVPR with current
@@ -463,6 +468,11 @@ _STATIC(__after_prom_start)
 #if defined(CONFIG_PPC_BOOK3E)
 	tovirt(r26,r26)			/* on booke, we already run at PAGE_OFFSET */
 #endif
+#if defined(CONFIG_KEXEC) || defined(CONFIG_CRASH_DUMP)
+	/* If relocated we need to restore this flag on that relocated address. */
+	ld	r7,__run_at_kexec-_stext(r3)
+	std	r7,__run_at_kexec-_stext(r26)
+#endif
 	lwz	r7,__run_at_load-_stext(r26)
 #if defined(CONFIG_PPC_BOOK3E)
 	tophys(r26,r26)			/* Restore for the remains. */
diff --git a/arch/powerpc/kernel/misc_64.S b/arch/powerpc/kernel/misc_64.S
index 049be29..adf60b6 100644
--- a/arch/powerpc/kernel/misc_64.S
+++ b/arch/powerpc/kernel/misc_64.S
@@ -639,6 +639,12 @@ _GLOBAL(kexec_sequence)
 	bl	.copy_and_flush	/* (dest, src, copy limit, start offset) */
 1:	/* assume normal blr return */
 
+	/* notify we're going into kexec kernel for SMP. */
+	LOAD_REG_ADDR(r3,__run_at_kexec)
+	li	r4,1
+	std	r4,0(r3)
+	sync
+
 	/* release other cpus to the new kernel secondary start at 0x60 */
 	mflr	r5
 	li	r6,1
diff --git a/arch/powerpc/platforms/85xx/smp.c b/arch/powerpc/platforms/85xx/smp.c
index ea9c626..549948a 100644
--- a/arch/powerpc/platforms/85xx/smp.c
+++ b/arch/powerpc/platforms/85xx/smp.c
@@ -150,6 +150,9 @@ static int smp_85xx_kick_cpu(int nr)
 	int hw_cpu = get_hard_smp_processor_id(nr);
 	int ioremappable;
 	int ret = 0;
+#ifdef CONFIG_PPC64
+	unsigned long *ptr = NULL;
+#endif
 
 	WARN_ON(nr < 0 || nr >= NR_CPUS);
 	WARN_ON(hw_cpu < 0 || hw_cpu >= NR_CPUS);
@@ -238,11 +241,18 @@ out:
 #else
 	smp_generic_kick_cpu(nr);
 
-	flush_spin_table(spin_table);
-	out_be32(&spin_table->pir, hw_cpu);
-	out_be64((u64 *)(&spin_table->addr_h),
-	  __pa((u64)*((unsigned long long *)generic_secondary_smp_init)));
-	flush_spin_table(spin_table);
+	ptr  = (unsigned long *)((unsigned long)&__run_at_kexec);
+	/* We shouldn't access spin_table from the bootloader to up any
+	 * secondary cpu for kexec kernel, and kexec kernel already
+	 * know how to jump to generic_secondary_smp_init.
+	 */
+	if (!*ptr) {
+		flush_spin_table(spin_table);
+		out_be32(&spin_table->pir, hw_cpu);
+		out_be64((u64 *)(&spin_table->addr_h),
+		 __pa((u64)*((unsigned long long *)generic_secondary_smp_init)));
+		flush_spin_table(spin_table);
+	}
 #endif
 
 	local_irq_restore(flags);
-- 
1.7.9.5

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