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authorPeter Zijlstra <peterz@infradead.org>2016-11-15 16:47:06 +0100
committerIngo Molnar <mingo@kernel.org>2016-11-22 12:48:11 +0100
commit3cded41794818d788aa1dc028ede4a1c1222d937 (patch)
treeb38f7540e28ee21ccec1e2fb850ff4235041984e /arch/x86/kernel/kvm.c
parent05ffc951392df57edecc2519327b169210c3df75 (diff)
downloadlinux-3cded41794818d788aa1dc028ede4a1c1222d937.tar.bz2
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/kvm.c')
-rw-r--r--arch/x86/kernel/kvm.c25
1 files changed, 13 insertions, 12 deletions
diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
index 0b48dd2c3554..52e90d6054fb 100644
--- a/arch/x86/kernel/kvm.c
+++ b/arch/x86/kernel/kvm.c
@@ -415,15 +415,6 @@ void kvm_disable_steal_time(void)
wrmsr(MSR_KVM_STEAL_TIME, 0, 0);
}
-static bool kvm_vcpu_is_preempted(int cpu)
-{
- struct kvm_steal_time *src;
-
- src = &per_cpu(steal_time, cpu);
-
- return !!src->preempted;
-}
-
#ifdef CONFIG_SMP
static void __init kvm_smp_prepare_boot_cpu(void)
{
@@ -480,9 +471,6 @@ void __init kvm_guest_init(void)
if (kvm_para_has_feature(KVM_FEATURE_STEAL_TIME)) {
has_steal_clock = 1;
pv_time_ops.steal_clock = kvm_steal_clock;
-#ifdef CONFIG_PARAVIRT_SPINLOCKS
- pv_lock_ops.vcpu_is_preempted = kvm_vcpu_is_preempted;
-#endif
}
if (kvm_para_has_feature(KVM_FEATURE_PV_EOI))
@@ -604,6 +592,14 @@ out:
local_irq_restore(flags);
}
+__visible bool __kvm_vcpu_is_preempted(int cpu)
+{
+ struct kvm_steal_time *src = &per_cpu(steal_time, cpu);
+
+ return !!src->preempted;
+}
+PV_CALLEE_SAVE_REGS_THUNK(__kvm_vcpu_is_preempted);
+
/*
* Setup pv_lock_ops to exploit KVM_FEATURE_PV_UNHALT if present.
*/
@@ -620,6 +616,11 @@ void __init kvm_spinlock_init(void)
pv_lock_ops.queued_spin_unlock = PV_CALLEE_SAVE(__pv_queued_spin_unlock);
pv_lock_ops.wait = kvm_wait;
pv_lock_ops.kick = kvm_kick_cpu;
+
+ if (kvm_para_has_feature(KVM_FEATURE_STEAL_TIME)) {
+ pv_lock_ops.vcpu_is_preempted =
+ PV_CALLEE_SAVE(__kvm_vcpu_is_preempted);
+ }
}
static __init int kvm_spinlock_init_jump(void)