context_tracking: avoid irq_save/irq_restore on guest entry and exit
guest_enter and guest_exit must be called with interrupts disabled,
since they take the vtime_seqlock with write_seq{lock,unlock}.
Therefore, it is not necessary to check for exceptions, nor to
save/restore the IRQ state, when context tracking functions are
called by guest_enter and guest_exit.
Split the body of context_tracking_entry and context_tracking_exit
out to __-prefixed functions, and use them from KVM.
Rik van Riel has measured this to speed up a tight vmentry/vmexit
loop by about 2%.
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Paul McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Rik van Riel <riel@redhat.com>
Tested-by: Rik van Riel <riel@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
diff --git a/include/linux/context_tracking.h b/include/linux/context_tracking.h
index 6ef136f..68b575a 100644
--- a/include/linux/context_tracking.h
+++ b/include/linux/context_tracking.h
@@ -10,6 +10,10 @@
#ifdef CONFIG_CONTEXT_TRACKING
extern void context_tracking_cpu_set(int cpu);
+/* Called with interrupts disabled. */
+extern void __context_tracking_enter(enum ctx_state state);
+extern void __context_tracking_exit(enum ctx_state state);
+
extern void context_tracking_enter(enum ctx_state state);
extern void context_tracking_exit(enum ctx_state state);
extern void context_tracking_user_enter(void);
@@ -88,13 +92,13 @@
current->flags |= PF_VCPU;
if (context_tracking_is_enabled())
- context_tracking_enter(CONTEXT_GUEST);
+ __context_tracking_enter(CONTEXT_GUEST);
}
static inline void guest_exit(void)
{
if (context_tracking_is_enabled())
- context_tracking_exit(CONTEXT_GUEST);
+ __context_tracking_exit(CONTEXT_GUEST);
if (vtime_accounting_enabled())
vtime_guest_exit(current);