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| author | Paolo Bonzini <pbonzini@redhat.com> | 2015-10-28 02:39:56 +0100 |
|---|---|---|
| committer | Paolo Bonzini <pbonzini@redhat.com> | 2015-11-10 12:06:23 +0100 |
| commit | d0e536d89395ecd8ab78fe999dc4d6f5d140ce46 (patch) | |
| tree | bac5690350e345061db0206bbbe91dbeeb6ebdad /include/linux | |
| parent | f70cd6b07e629f367bb9b1ac9d0e3e669eb325c0 (diff) | |
| download | lwn-d0e536d89395ecd8ab78fe999dc4d6f5d140ce46.tar.gz lwn-d0e536d89395ecd8ab78fe999dc4d6f5d140ce46.zip | |
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>
Diffstat (limited to 'include/linux')
| -rw-r--r-- | include/linux/context_tracking.h | 8 |
1 files changed, 6 insertions, 2 deletions
diff --git a/include/linux/context_tracking.h b/include/linux/context_tracking.h index 6ef136ff0897..68b575afe5f5 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 @@ 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); |