KVM: provide irq_unsafe kvm_guest_{enter|exit}
Several kvm architectures disable interrupts before kvm_guest_enter.
kvm_guest_enter then uses local_irq_save/restore to disable interrupts
again or for the first time. Lets provide underscore versions of
kvm_guest_{enter|exit} that assume being called locked.
kvm_guest_enter now disables interrupts for the full function and
thus we can remove the check for preemptible.
This patch then adopts s390/kvm to use local_irq_disable/enable calls
which are slighty cheaper that local_irq_save/restore and call these
new functions.
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index ad45054..efc16df 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -762,16 +762,10 @@
}
#endif
-static inline void kvm_guest_enter(void)
+/* must be called with irqs disabled */
+static inline void __kvm_guest_enter(void)
{
- unsigned long flags;
-
- BUG_ON(preemptible());
-
- local_irq_save(flags);
guest_enter();
- local_irq_restore(flags);
-
/* KVM does not hold any references to rcu protected data when it
* switches CPU into a guest mode. In fact switching to a guest mode
* is very similar to exiting to userspace from rcu point of view. In
@@ -783,12 +777,27 @@
rcu_virt_note_context_switch(smp_processor_id());
}
+/* must be called with irqs disabled */
+static inline void __kvm_guest_exit(void)
+{
+ guest_exit();
+}
+
+static inline void kvm_guest_enter(void)
+{
+ unsigned long flags;
+
+ local_irq_save(flags);
+ __kvm_guest_enter();
+ local_irq_restore(flags);
+}
+
static inline void kvm_guest_exit(void)
{
unsigned long flags;
local_irq_save(flags);
- guest_exit();
+ __kvm_guest_exit();
local_irq_restore(flags);
}