x86, mm: Patch out arch_flush_lazy_mmu_mode() when running on bare metal

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@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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/arch/x86/include/asm/paravirt.h b/arch/x86/include/asm/paravirt.h
index ebbc4d8ab1709e9427394f793af878cdd5cf9e66..2fdfe312b5dc52986ec99d4275c0feefa34b315f 100644 (file)
--- a/arch/x86/include/asm/paravirt.h
+++ b/arch/x86/include/asm/paravirt.h
@@ -731,7 +731,10 @@ static inline void arch_leave_lazy_mmu_mode(void)
        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)

diff --git a/arch/x86/include/asm/paravirt_types.h b/arch/x86/include/asm/paravirt_types.h
index 82885099c86934ca109799f010e83cfe021d0b7f..4b67ec957e8a4155853491c50e11ff9fa983957b 100644 (file)
--- a/arch/x86/include/asm/paravirt_types.h
+++ b/arch/x86/include/asm/paravirt_types.h
@@ -85,6 +85,7 @@ 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 {
@@ -673,6 +674,7 @@ void paravirt_end_context_switch(struct task_struct *next);
 
 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);

diff --git a/arch/x86/kernel/paravirt.c b/arch/x86/kernel/paravirt.c
index 869e1aeeb71bdc7e4059798bb0f3cdb89061c15c..704faba97c134a1cc76b224151ac4b7c5397630a 100644 (file)
--- a/arch/x86/kernel/paravirt.c
+++ b/arch/x86/kernel/paravirt.c
@@ -253,6 +253,18 @@ 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());
@@ -282,18 +294,6 @@ enum paravirt_lazy_mode paravirt_get_lazy_mode(void)
        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,
@@ -462,6 +462,7 @@ struct pv_mmu_ops pv_mmu_ops = {
        .lazy_mode = {
                .enter = paravirt_nop,
                .leave = paravirt_nop,
+               .flush = paravirt_nop,
        },
 
        .set_fixmap = native_set_fixmap,

diff --git a/arch/x86/lguest/boot.c b/arch/x86/lguest/boot.c
index db832fd65ecbf8d749720b449eed3fd2b8d55cab..2d452471b4afb481d71bc09b713c08497aef95e1 100644 (file)
--- a/arch/x86/lguest/boot.c
+++ b/arch/x86/lguest/boot.c
@@ -1309,6 +1309,7 @@ __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;
 

diff --git a/arch/x86/xen/mmu.c b/arch/x86/xen/mmu.c
index d957dce61ede0e7c8c6a6acf4ebfdfa783d474fa..a0aed70596a4b2dd1225f20b3e1952ec934388eb 100644 (file)
--- a/arch/x86/xen/mmu.c
+++ b/arch/x86/xen/mmu.c
@@ -2011,6 +2011,7 @@ static const struct pv_mmu_ops xen_mmu_ops __initconst = {
        .lazy_mode = {
                .enter = paravirt_enter_lazy_mmu,
                .leave = xen_leave_lazy_mmu,
+               .flush = paravirt_flush_lazy_mmu,
        },
 
        .set_fixmap = xen_set_fixmap,