| Message ID | 1426798361-14982-1-git-send-email-rkrcmar@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Thu, Mar 19, 2015 at 09:52:41PM +0100, Radim Kr?má? wrote: > An overhead from function call is not appropriate for its size and > frequency of execution. > > Suggested-by: Paolo Bonzini <pbonzini@redhat.com> > Signed-off-by: Radim Kr?má? <rkrcmar@redhat.com> > --- > I'm not very fond of that smp_rmb(): there is no real synchronization > against update_handled_vectors(), Yes, because the guest OS should provide synchronization (it should shutdown interrupts before attempting to modify IOAPIC table). The smp_wmb is necessary. > so the only point I see is to drop > cached value of handled_vectors, which seems like bad use of LFENCE. test_bit has volatile on *addr, so don't see why the smp_rmb is necessary at all. Applied, thanks. -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/arch/x86/kvm/ioapic.c b/arch/x86/kvm/ioapic.c index 1522bab6bcff..f04986e1a0b0 100644 --- a/arch/x86/kvm/ioapic.c +++ b/arch/x86/kvm/ioapic.c @@ -475,13 +475,6 @@ static void __kvm_ioapic_update_eoi(struct kvm_vcpu *vcpu, } } -bool kvm_ioapic_handles_vector(struct kvm *kvm, int vector) -{ - struct kvm_ioapic *ioapic = kvm->arch.vioapic; - smp_rmb(); - return test_bit(vector, ioapic->handled_vectors); -} - void kvm_ioapic_update_eoi(struct kvm_vcpu *vcpu, int vector, int trigger_mode) { struct kvm_ioapic *ioapic = vcpu->kvm->arch.vioapic; diff --git a/arch/x86/kvm/ioapic.h b/arch/x86/kvm/ioapic.h index 38d8402ea65c..6e265cfcd86a 100644 --- a/arch/x86/kvm/ioapic.h +++ b/arch/x86/kvm/ioapic.h @@ -98,13 +98,19 @@ static inline struct kvm_ioapic *ioapic_irqchip(struct kvm *kvm) return kvm->arch.vioapic; } +static inline bool kvm_ioapic_handles_vector(struct kvm *kvm, int vector) +{ + struct kvm_ioapic *ioapic = kvm->arch.vioapic; + smp_rmb(); + return test_bit(vector, ioapic->handled_vectors); +} + void kvm_rtc_eoi_tracking_restore_one(struct kvm_vcpu *vcpu); bool kvm_apic_match_dest(struct kvm_vcpu *vcpu, struct kvm_lapic *source, int short_hand, unsigned int dest, int dest_mode); int kvm_apic_compare_prio(struct kvm_vcpu *vcpu1, struct kvm_vcpu *vcpu2); void kvm_ioapic_update_eoi(struct kvm_vcpu *vcpu, int vector, int trigger_mode); -bool kvm_ioapic_handles_vector(struct kvm *kvm, int vector); int kvm_ioapic_init(struct kvm *kvm); void kvm_ioapic_destroy(struct kvm *kvm); int kvm_ioapic_set_irq(struct kvm_ioapic *ioapic, int irq, int irq_source_id,
An overhead from function call is not appropriate for its size and frequency of execution. Suggested-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Radim Kr?má? <rkrcmar@redhat.com> --- I'm not very fond of that smp_rmb(): there is no real synchronization against update_handled_vectors(), so the only point I see is to drop cached value of handled_vectors, which seems like bad use of LFENCE. Am I missing something? Thanks. arch/x86/kvm/ioapic.c | 7 ------- arch/x86/kvm/ioapic.h | 8 +++++++- 2 files changed, 7 insertions(+), 8 deletions(-)