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Diffstat (limited to 'arch/x86/kernel/alternative.c')
-rw-r--r--arch/x86/kernel/alternative.c40
1 files changed, 27 insertions, 13 deletions
diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c
index d6405e0842b..45d79ea890a 100644
--- a/arch/x86/kernel/alternative.c
+++ b/arch/x86/kernel/alternative.c
@@ -273,6 +273,7 @@ struct smp_alt_module {
};
static LIST_HEAD(smp_alt_modules);
static DEFINE_SPINLOCK(smp_alt);
+static int smp_mode = 1; /* protected by smp_alt */
void alternatives_smp_module_add(struct module *mod, char *name,
void *locks, void *locks_end,
@@ -341,12 +342,13 @@ void alternatives_smp_switch(int smp)
#ifdef CONFIG_LOCKDEP
/*
- * A not yet fixed binutils section handling bug prevents
- * alternatives-replacement from working reliably, so turn
- * it off:
+ * Older binutils section handling bug prevented
+ * alternatives-replacement from working reliably.
+ *
+ * If this still occurs then you should see a hang
+ * or crash shortly after this line:
*/
- printk("lockdep: not fixing up alternatives.\n");
- return;
+ printk("lockdep: fixing up alternatives.\n");
#endif
if (noreplace_smp || smp_alt_once)
@@ -354,21 +356,29 @@ void alternatives_smp_switch(int smp)
BUG_ON(!smp && (num_online_cpus() > 1));
spin_lock_irqsave(&smp_alt, flags);
- if (smp) {
+
+ /*
+ * Avoid unnecessary switches because it forces JIT based VMs to
+ * throw away all cached translations, which can be quite costly.
+ */
+ if (smp == smp_mode) {
+ /* nothing */
+ } else if (smp) {
printk(KERN_INFO "SMP alternatives: switching to SMP code\n");
- clear_bit(X86_FEATURE_UP, boot_cpu_data.x86_capability);
- clear_bit(X86_FEATURE_UP, cpu_data(0).x86_capability);
+ clear_cpu_cap(&boot_cpu_data, X86_FEATURE_UP);
+ clear_cpu_cap(&cpu_data(0), X86_FEATURE_UP);
list_for_each_entry(mod, &smp_alt_modules, next)
alternatives_smp_lock(mod->locks, mod->locks_end,
mod->text, mod->text_end);
} else {
printk(KERN_INFO "SMP alternatives: switching to UP code\n");
- set_bit(X86_FEATURE_UP, boot_cpu_data.x86_capability);
- set_bit(X86_FEATURE_UP, cpu_data(0).x86_capability);
+ set_cpu_cap(&boot_cpu_data, X86_FEATURE_UP);
+ set_cpu_cap(&cpu_data(0), X86_FEATURE_UP);
list_for_each_entry(mod, &smp_alt_modules, next)
alternatives_smp_unlock(mod->locks, mod->locks_end,
mod->text, mod->text_end);
}
+ smp_mode = smp;
spin_unlock_irqrestore(&smp_alt, flags);
}
@@ -431,8 +441,9 @@ void __init alternative_instructions(void)
if (smp_alt_once) {
if (1 == num_possible_cpus()) {
printk(KERN_INFO "SMP alternatives: switching to UP code\n");
- set_bit(X86_FEATURE_UP, boot_cpu_data.x86_capability);
- set_bit(X86_FEATURE_UP, cpu_data(0).x86_capability);
+ set_cpu_cap(&boot_cpu_data, X86_FEATURE_UP);
+ set_cpu_cap(&cpu_data(0), X86_FEATURE_UP);
+
alternatives_smp_unlock(__smp_locks, __smp_locks_end,
_text, _etext);
}
@@ -440,7 +451,10 @@ void __init alternative_instructions(void)
alternatives_smp_module_add(NULL, "core kernel",
__smp_locks, __smp_locks_end,
_text, _etext);
- alternatives_smp_switch(0);
+
+ /* Only switch to UP mode if we don't immediately boot others */
+ if (num_possible_cpus() == 1 || setup_max_cpus <= 1)
+ alternatives_smp_switch(0);
}
#endif
apply_paravirt(__parainstructions, __parainstructions_end);