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-rw-r--r--arch/i386/kernel/paravirt.c1
-rw-r--r--arch/i386/kernel/process.c25
-rw-r--r--include/asm-generic/pgtable.h13
-rw-r--r--include/asm-i386/paravirt.h15
-rw-r--r--kernel/sched.c7
5 files changed, 53 insertions, 8 deletions
diff --git a/arch/i386/kernel/paravirt.c b/arch/i386/kernel/paravirt.c
index 7329ec9fcc9..4dfdac4550d 100644
--- a/arch/i386/kernel/paravirt.c
+++ b/arch/i386/kernel/paravirt.c
@@ -545,6 +545,7 @@ struct paravirt_ops paravirt_ops = {
.apic_write_atomic = native_apic_write_atomic,
.apic_read = native_apic_read,
#endif
+ .set_lazy_mode = (void *)native_nop,
.flush_tlb_user = native_flush_tlb,
.flush_tlb_kernel = native_flush_tlb_global,
diff --git a/arch/i386/kernel/process.c b/arch/i386/kernel/process.c
index 23ae198dbbc..cfae587bf7d 100644
--- a/arch/i386/kernel/process.c
+++ b/arch/i386/kernel/process.c
@@ -670,14 +670,6 @@ struct task_struct fastcall * __switch_to(struct task_struct *prev_p, struct tas
load_TLS(next, cpu);
/*
- * Restore %gs if needed (which is common)
- */
- if (prev->gs | next->gs)
- loadsegment(gs, next->gs);
-
- write_pda(pcurrent, next_p);
-
- /*
* Now maybe handle debug registers and/or IO bitmaps
*/
if (unlikely((task_thread_info(next_p)->flags & _TIF_WORK_CTXSW)
@@ -686,6 +678,15 @@ struct task_struct fastcall * __switch_to(struct task_struct *prev_p, struct tas
disable_tsc(prev_p, next_p);
+ /*
+ * Leave lazy mode, flushing any hypercalls made here.
+ * This must be done before restoring TLS segments so
+ * the GDT and LDT are properly updated, and must be
+ * done before math_state_restore, so the TS bit is up
+ * to date.
+ */
+ arch_leave_lazy_cpu_mode();
+
/* 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
* chances of needing FPU soon are obviously high now
@@ -693,6 +694,14 @@ struct task_struct fastcall * __switch_to(struct task_struct *prev_p, struct tas
if (next_p->fpu_counter > 5)
math_state_restore();
+ /*
+ * Restore %gs if needed (which is common)
+ */
+ if (prev->gs | next->gs)
+ loadsegment(gs, next->gs);
+
+ write_pda(pcurrent, next_p);
+
return prev_p;
}
diff --git a/include/asm-generic/pgtable.h b/include/asm-generic/pgtable.h
index 9d774d07d95..00c23433b39 100644
--- a/include/asm-generic/pgtable.h
+++ b/include/asm-generic/pgtable.h
@@ -183,6 +183,19 @@ static inline void ptep_set_wrprotect(struct mm_struct *mm, unsigned long addres
#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.
+ */
+#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)
+#endif
+
+/*
* When walking page tables, get the address of the next boundary,
* or the end address of the range if that comes earlier. Although no
* vma end wraps to 0, rounded up __boundary may wrap to 0 throughout.
diff --git a/include/asm-i386/paravirt.h b/include/asm-i386/paravirt.h
index 53da276a2ec..38e5164bd0e 100644
--- a/include/asm-i386/paravirt.h
+++ b/include/asm-i386/paravirt.h
@@ -146,6 +146,8 @@ struct paravirt_ops
void (fastcall *pmd_clear)(pmd_t *pmdp);
#endif
+ void (fastcall *set_lazy_mode)(int mode);
+
/* These two are jmp to, not actually called. */
void (fastcall *irq_enable_sysexit)(void);
void (fastcall *iret)(void);
@@ -386,6 +388,19 @@ static inline void pmd_clear(pmd_t *pmdp)
}
#endif
+/* Lazy mode for batching updates / context switch */
+#define PARAVIRT_LAZY_NONE 0
+#define PARAVIRT_LAZY_MMU 1
+#define PARAVIRT_LAZY_CPU 2
+
+#define __HAVE_ARCH_ENTER_LAZY_CPU_MODE
+#define arch_enter_lazy_cpu_mode() paravirt_ops.set_lazy_mode(PARAVIRT_LAZY_CPU)
+#define arch_leave_lazy_cpu_mode() paravirt_ops.set_lazy_mode(PARAVIRT_LAZY_NONE)
+
+#define __HAVE_ARCH_ENTER_LAZY_MMU_MODE
+#define arch_enter_lazy_mmu_mode() paravirt_ops.set_lazy_mode(PARAVIRT_LAZY_MMU)
+#define arch_leave_lazy_mmu_mode() paravirt_ops.set_lazy_mode(PARAVIRT_LAZY_NONE)
+
/* These all sit in the .parainstructions section to tell us what to patch. */
struct paravirt_patch {
u8 *instr; /* original instructions */
diff --git a/kernel/sched.c b/kernel/sched.c
index 08f86178aa3..0dc757246d8 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -1853,6 +1853,13 @@ context_switch(struct rq *rq, struct task_struct *prev,
struct mm_struct *mm = next->mm;
struct mm_struct *oldmm = prev->active_mm;
+ /*
+ * For paravirt, this is coupled with an exit in switch_to to
+ * combine the page table reload and the switch backend into
+ * one hypercall.
+ */
+ arch_enter_lazy_cpu_mode();
+
if (!mm) {
next->active_mm = oldmm;
atomic_inc(&oldmm->mm_count);