From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: [PATCH] KVM: avoid taking ioapic mutex for non-ioapic EOIs Date: Mon, 28 Dec 2009 14:08:30 +0200 Message-ID: <1262002110-4240-1-git-send-email-avi@redhat.com> Cc: Gleb Natapov , kvm@vger.kernel.org To: Marcelo Tosatti Return-path: Received: from mx1.redhat.com ([209.132.183.28]:38069 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751020AbZL1MId (ORCPT ); Mon, 28 Dec 2009 07:08:33 -0500 Received: from int-mx05.intmail.prod.int.phx2.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.18]) by mx1.redhat.com (8.13.8/8.13.8) with ESMTP id nBSC8WEx031533 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK) for ; Mon, 28 Dec 2009 07:08:32 -0500 Sender: kvm-owner@vger.kernel.org List-ID: When the guest acknowledges an interrupt, it sends an EOI message to the local apic, which broadcasts it to the ioapic. To handle the EOI, we need to take the ioapic mutex. On large guests, this causes a lot of contention on this mutex. Since large guests usually don't route interrupts via the ioapic (they use msi instead), this is completely unnecessary. Avoid taking the mutex by introducing a handled_vectors bitmap. Before taking the mutex, check if the ioapic was actually responsible for the acked vector. If not, we can return early. Signed-off-by: Avi Kivity --- virt/kvm/ioapic.c | 19 +++++++++++++++++++ virt/kvm/ioapic.h | 1 + 2 files changed, 20 insertions(+), 0 deletions(-) diff --git a/virt/kvm/ioapic.c b/virt/kvm/ioapic.c index f01392f..a2edfd1 100644 --- a/virt/kvm/ioapic.c +++ b/virt/kvm/ioapic.c @@ -100,6 +100,19 @@ static int ioapic_service(struct kvm_ioapic *ioapic, unsigned int idx) return injected; } +static void update_handled_vectors(struct kvm_ioapic *ioapic) +{ + DECLARE_BITMAP(handled_vectors, 256); + int i; + + memset(handled_vectors, 0, sizeof(handled_vectors)); + for (i = 0; i < IOAPIC_NUM_PINS; ++i) + __set_bit(ioapic->redirtbl[i].fields.vector, handled_vectors); + memcpy(ioapic->handled_vectors, handled_vectors, + sizeof(handled_vectors)); + smp_wmb(); +} + static void ioapic_write_indirect(struct kvm_ioapic *ioapic, u32 val) { unsigned index; @@ -134,6 +147,7 @@ static void ioapic_write_indirect(struct kvm_ioapic *ioapic, u32 val) e->bits |= (u32) val; e->fields.remote_irr = 0; } + update_handled_vectors(ioapic); mask_after = e->fields.mask; if (mask_before != mask_after) kvm_fire_mask_notifiers(ioapic->kvm, index, mask_after); @@ -241,6 +255,9 @@ void kvm_ioapic_update_eoi(struct kvm *kvm, int vector, int trigger_mode) { struct kvm_ioapic *ioapic = kvm->arch.vioapic; + smp_rmb(); + if (!test_bit(vector, ioapic->handled_vectors)) + return; mutex_lock(&ioapic->lock); __kvm_ioapic_update_eoi(ioapic, vector, trigger_mode); mutex_unlock(&ioapic->lock); @@ -352,6 +369,7 @@ void kvm_ioapic_reset(struct kvm_ioapic *ioapic) ioapic->ioregsel = 0; ioapic->irr = 0; ioapic->id = 0; + update_handled_vectors(ioapic); } static const struct kvm_io_device_ops ioapic_mmio_ops = { @@ -401,6 +419,7 @@ int kvm_set_ioapic(struct kvm *kvm, struct kvm_ioapic_state *state) mutex_lock(&ioapic->lock); memcpy(ioapic, state, sizeof(struct kvm_ioapic_state)); + update_handled_vectors(ioapic); mutex_unlock(&ioapic->lock); return 0; } diff --git a/virt/kvm/ioapic.h b/virt/kvm/ioapic.h index 419c43b..a505ce9 100644 --- a/virt/kvm/ioapic.h +++ b/virt/kvm/ioapic.h @@ -46,6 +46,7 @@ struct kvm_ioapic { struct kvm *kvm; void (*ack_notifier)(void *opaque, int irq); struct mutex lock; + DECLARE_BITMAP(handled_vectors, 256); }; #ifdef DEBUG -- 1.6.5.3