x86/paravirt: allow preemption with lazy mmu mode
Impact: remove obsolete checks, simplification
Lift restrictions on preemption with lazy mmu mode, as it is now allowed.
Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
diff --git a/arch/x86/kernel/paravirt.c b/arch/x86/kernel/paravirt.c
index cf14375..bf2e86e 100644
--- a/arch/x86/kernel/paravirt.c
+++ b/arch/x86/kernel/paravirt.c
@@ -247,7 +247,6 @@
static inline void enter_lazy(enum paravirt_lazy_mode mode)
{
BUG_ON(__get_cpu_var(paravirt_lazy_mode) != PARAVIRT_LAZY_NONE);
- BUG_ON(preemptible());
__get_cpu_var(paravirt_lazy_mode) = mode;
}
@@ -255,7 +254,6 @@
static void leave_lazy(enum paravirt_lazy_mode mode)
{
BUG_ON(__get_cpu_var(paravirt_lazy_mode) != mode);
- BUG_ON(preemptible());
__get_cpu_var(paravirt_lazy_mode) = PARAVIRT_LAZY_NONE;
}
@@ -272,6 +270,8 @@
void paravirt_start_context_switch(struct task_struct *prev)
{
+ BUG_ON(preemptible());
+
if (percpu_read(paravirt_lazy_mode) == PARAVIRT_LAZY_MMU) {
arch_leave_lazy_mmu_mode();
set_ti_thread_flag(task_thread_info(prev), TIF_LAZY_MMU_UPDATES);
@@ -281,6 +281,8 @@
void paravirt_end_context_switch(struct task_struct *next)
{
+ BUG_ON(preemptible());
+
leave_lazy(PARAVIRT_LAZY_CPU);
if (test_and_clear_ti_thread_flag(task_thread_info(next), TIF_LAZY_MMU_UPDATES))
@@ -300,7 +302,6 @@
preempt_disable();
if (paravirt_get_lazy_mode() == PARAVIRT_LAZY_MMU) {
- WARN_ON(preempt_count() == 1);
arch_leave_lazy_mmu_mode();
arch_enter_lazy_mmu_mode();
}
diff --git a/arch/x86/xen/mmu.c b/arch/x86/xen/mmu.c
index f5f8faa..3f2d0fe 100644
--- a/arch/x86/xen/mmu.c
+++ b/arch/x86/xen/mmu.c
@@ -419,10 +419,6 @@
void xen_set_pte_at(struct mm_struct *mm, unsigned long addr,
pte_t *ptep, pte_t pteval)
{
- /* updates to init_mm may be done without lock */
- if (mm == &init_mm)
- preempt_disable();
-
ADD_STATS(set_pte_at, 1);
// ADD_STATS(set_pte_at_pinned, xen_page_pinned(ptep));
ADD_STATS(set_pte_at_current, mm == current->mm);
@@ -443,9 +439,7 @@
}
xen_set_pte(ptep, pteval);
-out:
- if (mm == &init_mm)
- preempt_enable();
+out: return;
}
pte_t xen_ptep_modify_prot_start(struct mm_struct *mm,