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authorBoris Ostrovsky <boris.ostrovsky@oracle.com>2013-03-23 09:36:36 -0400
committerH. Peter Anvin <hpa@linux.intel.com>2013-04-10 11:25:10 -0700
commit511ba86e1d386f671084b5d0e6f110bb30b8eeb2 (patch)
tree1fe3621ebaf43ad5fb5ab644500676f2f158153f /arch/x86/kernel/paravirt.c
parent1160c2779b826c6f5c08e5cc542de58fd1f667d5 (diff)
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x86, mm: Patch out arch_flush_lazy_mmu_mode() when running on bare metal
Invoking arch_flush_lazy_mmu_mode() results in calls to preempt_enable()/disable() which may have performance impact. Since lazy MMU is not used on bare metal we can patch away arch_flush_lazy_mmu_mode() so that it is never called in such environment. [ hpa: the previous patch "Fix vmalloc_fault oops during lazy MMU updates" may cause a minor performance regression on bare metal. This patch resolves that performance regression. It is somewhat unclear to me if this is a good -stable candidate. ] Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com> Link: http://lkml.kernel.org/r/1364045796-10720-2-git-send-email-konrad.wilk@oracle.com Tested-by: Josh Boyer <jwboyer@redhat.com> Tested-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> Acked-by: Borislav Petkov <bp@suse.de> Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> Signed-off-by: H. Peter Anvin <hpa@linux.intel.com> Cc: <stable@vger.kernel.org> SEE NOTE ABOVE
Diffstat (limited to 'arch/x86/kernel/paravirt.c')
-rw-r--r--arch/x86/kernel/paravirt.c25
1 files changed, 13 insertions, 12 deletions
diff --git a/arch/x86/kernel/paravirt.c b/arch/x86/kernel/paravirt.c
index 17fff18a103..8bfb335f74b 100644
--- a/arch/x86/kernel/paravirt.c
+++ b/arch/x86/kernel/paravirt.c
@@ -263,6 +263,18 @@ void paravirt_leave_lazy_mmu(void)
leave_lazy(PARAVIRT_LAZY_MMU);
}
+void paravirt_flush_lazy_mmu(void)
+{
+ preempt_disable();
+
+ if (paravirt_get_lazy_mode() == PARAVIRT_LAZY_MMU) {
+ arch_leave_lazy_mmu_mode();
+ arch_enter_lazy_mmu_mode();
+ }
+
+ preempt_enable();
+}
+
void paravirt_start_context_switch(struct task_struct *prev)
{
BUG_ON(preemptible());
@@ -292,18 +304,6 @@ enum paravirt_lazy_mode paravirt_get_lazy_mode(void)
return this_cpu_read(paravirt_lazy_mode);
}
-void arch_flush_lazy_mmu_mode(void)
-{
- preempt_disable();
-
- if (paravirt_get_lazy_mode() == PARAVIRT_LAZY_MMU) {
- arch_leave_lazy_mmu_mode();
- arch_enter_lazy_mmu_mode();
- }
-
- preempt_enable();
-}
-
struct pv_info pv_info = {
.name = "bare hardware",
.paravirt_enabled = 0,
@@ -475,6 +475,7 @@ struct pv_mmu_ops pv_mmu_ops = {
.lazy_mode = {
.enter = paravirt_nop,
.leave = paravirt_nop,
+ .flush = paravirt_nop,
},
.set_fixmap = native_set_fixmap,