diff options
| author | Peter Zijlstra <peterz@infradead.org> | 2016-11-15 16:47:06 +0100 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2016-11-22 12:48:11 +0100 |
| commit | 3cded41794818d788aa1dc028ede4a1c1222d937 (patch) | |
| tree | b38f7540e28ee21ccec1e2fb850ff4235041984e /arch/x86/kernel/paravirt-spinlocks.c | |
| parent | locking/mutex: Break out of expensive busy-loop on {mutex,rwsem}_spin_on_owne... (diff) | |
| download | linux-3cded41794818d788aa1dc028ede4a1c1222d937.tar.xz linux-3cded41794818d788aa1dc028ede4a1c1222d937.zip | |
x86/paravirt: Optimize native pv_lock_ops.vcpu_is_preempted()
Avoid the pointless function call to pv_lock_ops.vcpu_is_preempted()
when a paravirt spinlock enabled kernel is ran on native hardware.
Do this by patching out the CALL instruction with "XOR %RAX,%RAX"
which has the same effect (0 return value).
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: David.Laight@ACULAB.COM
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Pan Xinhui <xinhui.pan@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: benh@kernel.crashing.org
Cc: boqun.feng@gmail.com
Cc: borntraeger@de.ibm.com
Cc: bsingharora@gmail.com
Cc: dave@stgolabs.net
Cc: jgross@suse.com
Cc: kernellwp@gmail.com
Cc: konrad.wilk@oracle.com
Cc: mpe@ellerman.id.au
Cc: paulmck@linux.vnet.ibm.com
Cc: paulus@samba.org
Cc: pbonzini@redhat.com
Cc: rkrcmar@redhat.com
Cc: will.deacon@arm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'arch/x86/kernel/paravirt-spinlocks.c')
| -rw-r--r-- | arch/x86/kernel/paravirt-spinlocks.c | 14 |
1 files changed, 10 insertions, 4 deletions
diff --git a/arch/x86/kernel/paravirt-spinlocks.c b/arch/x86/kernel/paravirt-spinlocks.c index 2f204dd552a4..6d4bf812af45 100644 --- a/arch/x86/kernel/paravirt-spinlocks.c +++ b/arch/x86/kernel/paravirt-spinlocks.c @@ -12,7 +12,6 @@ __visible void __native_queued_spin_unlock(struct qspinlock *lock) { native_queued_spin_unlock(lock); } - PV_CALLEE_SAVE_REGS_THUNK(__native_queued_spin_unlock); bool pv_is_native_spin_unlock(void) @@ -21,9 +20,16 @@ bool pv_is_native_spin_unlock(void) __raw_callee_save___native_queued_spin_unlock; } -static bool native_vcpu_is_preempted(int cpu) +__visible bool __native_vcpu_is_preempted(int cpu) +{ + return false; +} +PV_CALLEE_SAVE_REGS_THUNK(__native_vcpu_is_preempted); + +bool pv_is_native_vcpu_is_preempted(void) { - return 0; + return pv_lock_ops.vcpu_is_preempted.func == + __raw_callee_save___native_vcpu_is_preempted; } struct pv_lock_ops pv_lock_ops = { @@ -32,7 +38,7 @@ struct pv_lock_ops pv_lock_ops = { .queued_spin_unlock = PV_CALLEE_SAVE(__native_queued_spin_unlock), .wait = paravirt_nop, .kick = paravirt_nop, - .vcpu_is_preempted = native_vcpu_is_preempted, + .vcpu_is_preempted = PV_CALLEE_SAVE(__native_vcpu_is_preempted), #endif /* SMP */ }; EXPORT_SYMBOL(pv_lock_ops); |