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Subject[patch 5/6] Allow boot-time disable of SMP altinstructions
Add "noreplace-smp" to disable SMP instruction replacement.

Signed-off-by: Jeremy Fitzhardinge <jeremy@xensource.com>

---
Documentation/kernel-parameters.txt | 6 ++++++
arch/i386/kernel/alternative.c | 23 +++++++++++++++++++----
2 files changed, 25 insertions(+), 4 deletions(-)
===================================================================
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -1134,6 +1134,9 @@ and is between 256 and 4096 characters.
nomca [IA-64] Disable machine check abort handling

nomce [IA-32] Machine Check Exception
+
+ noreplace-smp [IA-32,SMP] Don't replace SMP instructions
+ with UP alternatives

noresidual [PPC] Don't use residual data on PReP machines.

@@ -1540,6 +1543,9 @@ and is between 256 and 4096 characters.
smart2= [HW]
Format: <io1>[,<io2>[,...,<io8>]]

+ smp-alt-once [IA-32,SMP] On a hotplug CPU system, only
+ attempt to substitute SMP alternatives once at boot.
+
snd-ad1816a= [HW,ALSA]

snd-ad1848= [HW,ALSA]
===================================================================
--- a/arch/i386/kernel/alternative.c
+++ b/arch/i386/kernel/alternative.c
@@ -5,6 +5,7 @@
#include <asm/alternative.h>
#include <asm/sections.h>

+static int noreplace_smp = 0;
static int smp_alt_once = 0;
static int debug_alternative = 0;

@@ -13,14 +14,22 @@ static int __init bootonly(char *str)
smp_alt_once = 1;
return 1;
}
+__setup("smp-alt-boot", bootonly);
+
static int __init debug_alt(char *str)
{
debug_alternative = 1;
return 1;
}
-
-__setup("smp-alt-boot", bootonly);
__setup("debug-alternative", debug_alt);
+
+static int __init setup_noreplace_smp(char *str)
+{
+ noreplace_smp = 1;
+ return 1;
+}
+__setup("noreplace-smp", setup_noreplace_smp);
+

#define DPRINTK(fmt, args...) if (debug_alternative) \
printk(KERN_DEBUG fmt, args)
@@ -185,6 +194,9 @@ static void alternatives_smp_unlock(u8 *
{
u8 **ptr;

+ if (noreplace_smp)
+ return;
+
for (ptr = start; ptr < end; ptr++) {
if (*ptr < text)
continue;
@@ -218,6 +230,9 @@ void alternatives_smp_module_add(struct
{
struct smp_alt_module *smp;
unsigned long flags;
+
+ if (noreplace_smp)
+ return;

if (smp_alt_once) {
if (boot_cpu_has(X86_FEATURE_UP))
@@ -253,7 +268,7 @@ void alternatives_smp_module_del(struct
struct smp_alt_module *item;
unsigned long flags;

- if (smp_alt_once)
+ if (smp_alt_once || noreplace_smp)
return;

spin_lock_irqsave(&smp_alt, flags);
@@ -284,7 +299,7 @@ void alternatives_smp_switch(int smp)
return;
#endif

- if (smp_alt_once)
+ if (noreplace_smp || smp_alt_once)
return;
BUG_ON(!smp && (num_online_cpus() > 1));

--

-
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