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context_tracking: avoid irq_save/irq_restore on guest entry and exit

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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>
This commit is contained in:
Paolo Bonzini
2015-10-28 02:39:56 +01:00
parent f70cd6b07e
commit d0e536d893
2 changed files with 44 additions and 28 deletions
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8
include/linux/context_tracking.h
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@@ -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 @@ static inline void guest_enter(void)
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);