This is a note to let you know that I've just added the patch titled
x86, mm: Patch out arch_flush_lazy_mmu_mode() when running on bare metal
to the 3.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
x86-mm-patch-out-arch_flush_lazy_mmu_mode-when-running-on-bare-metal.patch
and it can be found in the queue-3.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 511ba86e1d386f671084b5d0e6f110bb30b8eeb2 Mon Sep 17 00:00:00 2001
From: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
Date: Sat, 23 Mar 2013 09:36:36 -0400
Subject: x86, mm: Patch out arch_flush_lazy_mmu_mode() when running on bare metal
From: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
commit 511ba86e1d386f671084b5d0e6f110bb30b8eeb2 upstream.
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@xxxxxxxxxx>
Link: http://lkml.kernel.org/r/1364045796-10720-2-git-send-email-konrad.wilk@xxxxxxxxxx
Tested-by: Josh Boyer <jwboyer@xxxxxxxxxx>
Tested-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
Acked-by: Borislav Petkov <bp@xxxxxxx>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
Signed-off-by: H. Peter Anvin <hpa@xxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/x86/include/asm/paravirt.h | 5 ++++-
arch/x86/include/asm/paravirt_types.h | 2 ++
arch/x86/kernel/paravirt.c | 25 +++++++++++++------------
arch/x86/lguest/boot.c | 1 +
arch/x86/xen/mmu.c | 1 +
5 files changed, 21 insertions(+), 13 deletions(-)
--- a/arch/x86/include/asm/paravirt.h
+++ b/arch/x86/include/asm/paravirt.h
@@ -741,7 +741,10 @@ static inline void arch_leave_lazy_mmu_m
PVOP_VCALL0(pv_mmu_ops.lazy_mode.leave);
}
-void arch_flush_lazy_mmu_mode(void);
+static inline void arch_flush_lazy_mmu_mode(void)
+{
+ PVOP_VCALL0(pv_mmu_ops.lazy_mode.flush);
+}
static inline void __set_fixmap(unsigned /* enum fixed_addresses */ idx,
phys_addr_t phys, pgprot_t flags)
--- a/arch/x86/include/asm/paravirt_types.h
+++ b/arch/x86/include/asm/paravirt_types.h
@@ -91,6 +91,7 @@ struct pv_lazy_ops {
/* Set deferred update mode, used for batching operations. */
void (*enter)(void);
void (*leave)(void);
+ void (*flush)(void);
};
struct pv_time_ops {
@@ -680,6 +681,7 @@ void paravirt_end_context_switch(struct
void paravirt_enter_lazy_mmu(void);
void paravirt_leave_lazy_mmu(void);
+void paravirt_flush_lazy_mmu(void);
void _paravirt_nop(void);
u32 _paravirt_ident_32(u32);
--- 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_laz
return percpu_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,
@@ -477,6 +477,7 @@ struct pv_mmu_ops pv_mmu_ops = {
.lazy_mode = {
.enter = paravirt_nop,
.leave = paravirt_nop,
+ .flush = paravirt_nop,
},
.set_fixmap = native_set_fixmap,
--- a/arch/x86/lguest/boot.c
+++ b/arch/x86/lguest/boot.c
@@ -1333,6 +1333,7 @@ __init void lguest_init(void)
pv_mmu_ops.read_cr3 = lguest_read_cr3;
pv_mmu_ops.lazy_mode.enter = paravirt_enter_lazy_mmu;
pv_mmu_ops.lazy_mode.leave = lguest_leave_lazy_mmu_mode;
+ pv_mmu_ops.lazy_mode.flush = paravirt_flush_lazy_mmu;
pv_mmu_ops.pte_update = lguest_pte_update;
pv_mmu_ops.pte_update_defer = lguest_pte_update;
--- a/arch/x86/xen/mmu.c
+++ b/arch/x86/xen/mmu.c
@@ -2076,6 +2076,7 @@ static const struct pv_mmu_ops xen_mmu_o
.lazy_mode = {
.enter = paravirt_enter_lazy_mmu,
.leave = xen_leave_lazy_mmu,
+ .flush = paravirt_flush_lazy_mmu,
},
.set_fixmap = xen_set_fixmap,
Patches currently in stable-queue which might be from boris.ostrovsky@xxxxxxxxxx are
queue-3.4/x86-mm-patch-out-arch_flush_lazy_mmu_mode-when-running-on-bare-metal.patch
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