[Xen-devel] [PATCH 4/9] x86/pvops: replace arch_enter_lazy_cpu_mode with arch_start_context_switch

[Jeremy Fitzhardinge <jeremy@xxxxxxxx>]

From: Jeremy Fitzhardinge <jeremy.fitzhardinge@xxxxxxxxxx>

Make lazy cpu mode more specific to context switching, so that
it makes sense to do more context-switch specific things in
the callbacks.

Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@xxxxxxxxxx>
---
 arch/x86/include/asm/paravirt.h |    8 +++-----
 arch/x86/kernel/paravirt.c      |   13 -------------
 arch/x86/kernel/process_32.c    |    2 +-
 arch/x86/kernel/process_64.c    |    2 +-
 arch/x86/xen/mmu.c              |    5 +----
 include/asm-frv/pgtable.h       |    4 ++--
 include/asm-generic/pgtable.h   |   21 +++++++++++----------
 kernel/sched.c                  |    2 +-
 8 files changed, 20 insertions(+), 37 deletions(-)

diff --git a/arch/x86/include/asm/paravirt.h b/arch/x86/include/asm/paravirt.h
index 0617d5c..7b28aba 100644
--- a/arch/x86/include/asm/paravirt.h
+++ b/arch/x86/include/asm/paravirt.h
@@ -1420,19 +1420,17 @@ void paravirt_enter_lazy_mmu(void);
 void paravirt_leave_lazy_mmu(void);
 void paravirt_leave_lazy(enum paravirt_lazy_mode mode);
 
-#define  __HAVE_ARCH_ENTER_LAZY_CPU_MODE
-static inline void arch_enter_lazy_cpu_mode(void)
+#define  __HAVE_ARCH_START_CONTEXT_SWITCH
+static inline void arch_start_context_switch(void)
 {
        PVOP_VCALL0(pv_cpu_ops.lazy_mode.enter);
 }
 
-static inline void arch_leave_lazy_cpu_mode(void)
+static inline void arch_end_context_switch(void)
 {
        PVOP_VCALL0(pv_cpu_ops.lazy_mode.leave);
 }
 
-void arch_flush_lazy_cpu_mode(void);
-
 #define  __HAVE_ARCH_ENTER_LAZY_MMU_MODE
 static inline void arch_enter_lazy_mmu_mode(void)
 {
diff --git a/arch/x86/kernel/paravirt.c b/arch/x86/kernel/paravirt.c
index 83dadf9..ef3ca17 100644
--- a/arch/x86/kernel/paravirt.c
+++ b/arch/x86/kernel/paravirt.c
@@ -302,19 +302,6 @@ void arch_flush_lazy_mmu_mode(void)
        preempt_enable();
 }
 
-void arch_flush_lazy_cpu_mode(void)
-{
-       preempt_disable();
-
-       if (paravirt_get_lazy_mode() == PARAVIRT_LAZY_CPU) {
-               WARN_ON(preempt_count() == 1);
-               arch_leave_lazy_cpu_mode();
-               arch_enter_lazy_cpu_mode();
-       }
-
-       preempt_enable();
-}
-
 struct pv_info pv_info = {
        .name = "bare hardware",
        .paravirt_enabled = 0,
diff --git a/arch/x86/kernel/process_32.c b/arch/x86/kernel/process_32.c
index 8a09fa0..60d7b18 100644
--- a/arch/x86/kernel/process_32.c
+++ b/arch/x86/kernel/process_32.c
@@ -578,7 +578,7 @@ __switch_to(struct task_struct *prev_p, struct task_struct 
*next_p)
         * done before math_state_restore, so the TS bit is up
         * to date.
         */
-       arch_leave_lazy_cpu_mode();
+       arch_end_context_switch();
 
        /* If the task has used fpu the last 5 timeslices, just do a full
         * restore of the math state immediately to avoid the trap; the
diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c
index 836ef65..d5156e7 100644
--- a/arch/x86/kernel/process_64.c
+++ b/arch/x86/kernel/process_64.c
@@ -595,7 +595,7 @@ __switch_to(struct task_struct *prev_p, struct task_struct 
*next_p)
         * done before math_state_restore, so the TS bit is up
         * to date.
         */
-       arch_leave_lazy_cpu_mode();
+       arch_end_context_switch();
 
        /*
         * Switch FS and GS.
diff --git a/arch/x86/xen/mmu.c b/arch/x86/xen/mmu.c
index 319bd40..298b9f5 100644
--- a/arch/x86/xen/mmu.c
+++ b/arch/x86/xen/mmu.c
@@ -1112,10 +1112,8 @@ static void drop_other_mm_ref(void *info)
 
        /* If this cpu still has a stale cr3 reference, then make sure
           it has been flushed. */
-       if (percpu_read(xen_current_cr3) == __pa(mm->pgd)) {
+       if (percpu_read(xen_current_cr3) == __pa(mm->pgd))
                load_cr3(swapper_pg_dir);
-               arch_flush_lazy_cpu_mode();
-       }
 }
 
 static void xen_drop_mm_ref(struct mm_struct *mm)
@@ -1128,7 +1126,6 @@ static void xen_drop_mm_ref(struct mm_struct *mm)
                        load_cr3(swapper_pg_dir);
                else
                        leave_mm(smp_processor_id());
-               arch_flush_lazy_cpu_mode();
        }
 
        /* Get the "official" set of cpus referring to our pagetable. */
diff --git a/include/asm-frv/pgtable.h b/include/asm-frv/pgtable.h
index 83c51ab..88bec28 100644
--- a/include/asm-frv/pgtable.h
+++ b/include/asm-frv/pgtable.h
@@ -73,8 +73,8 @@ static inline int pte_file(pte_t pte) { return 0; }
 #define pgtable_cache_init()           do {} while (0)
 #define arch_enter_lazy_mmu_mode()     do {} while (0)
 #define arch_leave_lazy_mmu_mode()     do {} while (0)
-#define arch_enter_lazy_cpu_mode()     do {} while (0)
-#define arch_leave_lazy_cpu_mode()     do {} while (0)
+
+#define arch_start_context_switch()    do {} while (0)
 
 #else /* !CONFIG_MMU */
 /*****************************************************************************/
diff --git a/include/asm-generic/pgtable.h b/include/asm-generic/pgtable.h
index 8e6d0ca..922f036 100644
--- a/include/asm-generic/pgtable.h
+++ b/include/asm-generic/pgtable.h
@@ -280,17 +280,18 @@ static inline void ptep_modify_prot_commit(struct 
mm_struct *mm,
 #endif
 
 /*
- * A facility to provide batching of the reload of page tables with the
- * actual context switch code for paravirtualized guests.  By convention,
- * only one of the lazy modes (CPU, MMU) should be active at any given
- * time, entry should never be nested, and entry and exits should always
- * be paired.  This is for sanity of maintaining and reasoning about the
- * kernel code.
+ * A facility to provide batching of the reload of page tables and
+ * other process state with the actual context switch code for
+ * paravirtualized guests.  By convention, only one of the batched
+ * update (lazy) modes (CPU, MMU) should be active at any given time,
+ * entry should never be nested, and entry and exits should always be
+ * paired.  This is for sanity of maintaining and reasoning about the
+ * kernel code.  In this case, the exit (end of the context switch) is
+ * in architecture-specific code, and so doesn't need a generic
+ * definition.
  */
-#ifndef __HAVE_ARCH_ENTER_LAZY_CPU_MODE
-#define arch_enter_lazy_cpu_mode()     do {} while (0)
-#define arch_leave_lazy_cpu_mode()     do {} while (0)
-#define arch_flush_lazy_cpu_mode()     do {} while (0)
+#ifndef __HAVE_ARCH_START_CONTEXT_SWITCH
+#define arch_start_context_switch()    do {} while (0)
 #endif
 
 #ifndef __HAVE_PFNMAP_TRACKING
diff --git a/kernel/sched.c b/kernel/sched.c
index a345d40..25d4c6b 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -2782,7 +2782,7 @@ context_switch(struct rq *rq, struct task_struct *prev,
         * combine the page table reload and the switch backend into
         * one hypercall.
         */
-       arch_enter_lazy_cpu_mode();
+       arch_start_context_switch();
 
        if (unlikely(!mm)) {
                next->active_mm = oldmm;
-- 
1.6.0.6


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