Use try_cmpxchg64() instead of cmpxchg64() to reuse flags from cmpxchg/cmpxchg8b instruction. For 64 bit targets flags reuse avoids a CMP instruction, while for 32 bit targets flags reuse avoids XOR/XOR/OR instruction sequence.
Signed-off-by: Uros Bizjak <[email protected]> Cc: Paolo Bonzini <[email protected]> Cc: Sean Christopherson <[email protected]> Cc: Vitaly Kuznetsov <[email protected]> Cc: Wanpeng Li <[email protected]> Cc: Jim Mattson <[email protected]> Cc: Joerg Roedel <[email protected]> --- arch/x86/kvm/vmx/posted_intr.c | 9 +++------ 1 file changed, 3 insertions(+), 6 deletions(-) diff --git a/arch/x86/kvm/vmx/posted_intr.c b/arch/x86/kvm/vmx/posted_intr.c index f02962dcc72c..47b47970fb46 100644 --- a/arch/x86/kvm/vmx/posted_intr.c +++ b/arch/x86/kvm/vmx/posted_intr.c @@ -60,8 +60,7 @@ void vmx_vcpu_pi_load(struct kvm_vcpu *vcpu, int cpu) new.ndst = (dest << 8) & 0xFF00; new.sn = 0; - } while (cmpxchg64(&pi_desc->control, old.control, - new.control) != old.control); + } while (!try_cmpxchg64(&pi_desc->control, &old.control, new.control)); after_clear_sn: @@ -111,8 +110,7 @@ static void __pi_post_block(struct kvm_vcpu *vcpu) /* set 'NV' to 'notification vector' */ new.nv = POSTED_INTR_VECTOR; - } while (cmpxchg64(&pi_desc->control, old.control, - new.control) != old.control); + } while (!try_cmpxchg64(&pi_desc->control, &old.control, new.control)); if (!WARN_ON_ONCE(vcpu->pre_pcpu == -1)) { spin_lock(&per_cpu(blocked_vcpu_on_cpu_lock, vcpu->pre_pcpu)); @@ -181,8 +179,7 @@ int pi_pre_block(struct kvm_vcpu *vcpu) /* set 'NV' to 'wakeup vector' */ new.nv = POSTED_INTR_WAKEUP_VECTOR; - } while (cmpxchg64(&pi_desc->control, old.control, - new.control) != old.control); + } while (!try_cmpxchg64(&pi_desc->control, &old.control, new.control)); /* We should not block the vCPU if an interrupt is posted for it. */ if (pi_test_on(pi_desc) == 1) -- 2.26.2
