From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756562Ab2ASMEn (ORCPT ); Thu, 19 Jan 2012 07:04:43 -0500 Received: from david.siemens.de ([192.35.17.14]:21311 "EHLO david.siemens.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751432Ab2ASMEk (ORCPT ); Thu, 19 Jan 2012 07:04:40 -0500 Message-ID: <4F1806D0.9020208@siemens.com> Date: Thu, 19 Jan 2012 13:04:32 +0100 From: Jan Kiszka User-Agent: Mozilla/5.0 (X11; U; Linux i686 (x86_64); de; rv:1.8.1.12) Gecko/20080226 SUSE/2.0.0.12-1.1 Thunderbird/2.0.0.12 Mnenhy/0.7.5.666 MIME-Version: 1.0 To: "Michael S. Tsirkin" CC: Alex Williamson , Avi Kivity , Marcelo Tosatti , "kvm@vger.kernel.org" , "linux-kernel@vger.kernel.org" Subject: Re: [PATCH RFC] kvm: deliver msix interrupts from irq handler References: <20120118181023.GA4140@redhat.com> In-Reply-To: <20120118181023.GA4140@redhat.com> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2012-01-18 19:10, Michael S. Tsirkin wrote: > We can deliver certain interrupts, notably MSIX, > from atomic context. Add a new API kvm_set_irq_inatomic, > that does exactly that, and use it to implement > an irq handler for msi. > > This reduces the pressure on scheduler in case > where host and guest irq share a host cpu. > > Signed-off-by: Michael S. Tsirkin > > Untested. > Note: this is on top of my host irq patch. > Probably needs to be rebased to be independent > and split up to new API + usage. > > --- > include/linux/kvm_host.h | 2 + > virt/kvm/assigned-dev.c | 31 +++++++++++++++++++++++++- > virt/kvm/irq_comm.c | 52 ++++++++++++++++++++++++++++++++++++++++++++++ > 3 files changed, 83 insertions(+), 2 deletions(-) > > diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h > index f0361bc..e2b89ea 100644 > --- a/include/linux/kvm_host.h > +++ b/include/linux/kvm_host.h > @@ -548,6 +548,8 @@ void kvm_get_intr_delivery_bitmask(struct kvm_ioapic *ioapic, > #endif > int kvm_set_irq(struct kvm *kvm, int irq_source_id, u32 irq, int level, > int host_irq); > +int kvm_set_irq_inatomic(struct kvm *kvm, int irq_source_id, u32 irq, int level, > + int host_irq); > int kvm_set_msi(struct kvm_kernel_irq_routing_entry *irq_entry, struct kvm *kvm, > int irq_source_id, int level, int host_irq); > void kvm_notify_acked_irq(struct kvm *kvm, unsigned irqchip, unsigned pin); > diff --git a/virt/kvm/assigned-dev.c b/virt/kvm/assigned-dev.c > index cc4bb7a..73bb001 100644 > --- a/virt/kvm/assigned-dev.c > +++ b/virt/kvm/assigned-dev.c > @@ -57,6 +57,14 @@ static int find_index_from_host_irq(struct kvm_assigned_dev_kernel > return index; > } > > +static irqreturn_t kvm_assigned_dev_msi(int irq, void *dev_id) > +{ > + int ret = kvm_set_irq_inatomic(assigned_dev->kvm, > + assigned_dev->irq_source_id, > + assigned_dev->guest_irq, 1, irq); > + return unlikely(ret == -EWOULDBLOCK) ? IRQ_WAKE_THREAD : IRQ_HANDLED; > +} This function gets unused (in theory) if !__KVM_HAVE_MSIX && !__KVM_HAVE_MSI. Should be fixed for consistency reasons. > + > static irqreturn_t kvm_assigned_dev_thread(int irq, void *dev_id) > { > struct kvm_assigned_dev_kernel *assigned_dev = dev_id; > @@ -75,6 +83,23 @@ static irqreturn_t kvm_assigned_dev_thread(int irq, void *dev_id) > } > > #ifdef __KVM_HAVE_MSIX > +static irqreturn_t kvm_assigned_dev_msix(int irq, void *dev_id) > +{ > + struct kvm_assigned_dev_kernel *assigned_dev = dev_id; > + int index = find_index_from_host_irq(assigned_dev, irq); > + u32 vector; > + int ret = 0; > + > + if (index >= 0) { > + vector = assigned_dev->guest_msix_entries[index].vector; > + ret = kvm_set_irq_inatomic(assigned_dev->kvm, > + assigned_dev->irq_source_id, > + vector, 1, irq); > + } > + > + return unlikely(ret == -EWOULDBLOCK) ? IRQ_WAKE_THREAD : IRQ_HANDLED; > +} > + > static irqreturn_t kvm_assigned_dev_thread_msix(int irq, void *dev_id) > { > struct kvm_assigned_dev_kernel *assigned_dev = dev_id; > @@ -266,7 +291,8 @@ static int assigned_device_enable_host_msi(struct kvm *kvm, > } > > dev->host_irq = dev->dev->irq; > - if (request_threaded_irq(dev->host_irq, NULL, kvm_assigned_dev_thread, > + if (request_threaded_irq(dev->host_irq, kvm_assigned_dev_msi, > + kvm_assigned_dev_thread, > 0, dev->irq_name, dev)) { > pci_disable_msi(dev->dev); > return -EIO; > @@ -293,7 +319,8 @@ static int assigned_device_enable_host_msix(struct kvm *kvm, > > for (i = 0; i < dev->entries_nr; i++) { > r = request_threaded_irq(dev->host_msix_entries[i].vector, > - NULL, kvm_assigned_dev_thread_msix, > + kvm_assigned_dev_msix, > + kvm_assigned_dev_thread_msix, > 0, dev->irq_name, dev); > if (r) > goto err; > diff --git a/virt/kvm/irq_comm.c b/virt/kvm/irq_comm.c > index ba892df..68cd127 100644 > --- a/virt/kvm/irq_comm.c > +++ b/virt/kvm/irq_comm.c > @@ -201,6 +201,58 @@ int kvm_set_irq(struct kvm *kvm, int irq_source_id, u32 irq, int level, > return ret; > } > > +static inline struct kvm_kernel_irq_routing_entry * > +kvm_get_entry(struct kvm *kvm, struct kvm_irq_routing_table *irq_rq, u32 irq) > +{ > + struct kvm_kernel_irq_routing_entry *e; > + if (likely(irq < irq_rt->nr_rt_entries)) > + hlist_for_each_entry(e, n, &irq_rt->map[irq], link) > + if (e->type == KVM_IRQ_ROUTING_MSI) > + return e; > + else > + return ERR_PTR(-EWOULDBLOCK); > + return ERR_PTR(-EINVAL); > +} > + > +/* > + * Deliver an IRQ in an atomic context if we can, or return a failure, > + * user can retry in a process context. > + * Return value: > + * -EWOULDBLOCK Can't deliver in atomic context > + * < 0 Interrupt was ignored (masked or not delivered for other reasons) > + * = 0 Interrupt was coalesced (previous irq is still pending) > + * > 0 Number of CPUs interrupt was delivered to Where do you make use of =0 vs. >0? Not in this patch at least. Do you consider using it for the APIC timer as well? > + */ > +int kvm_set_irq_inatomic(struct kvm *kvm, int irq_source_id, u32 irq, int level, > + int host_irq) > +{ > + struct kvm_kernel_irq_routing_entry *e; > + int ret = -EINVAL; > + struct kvm_irq_routing_table *irq_rt; > + struct hlist_node *n; > + > + trace_kvm_set_irq(irq, level, irq_source_id); > + > + /* > + * We know MSI are safe in interrupt context. They are also > + * easy as there's a single routing entry for these GSIs. > + * So only handle MSI in an atomic context, for now. > + */ > + rcu_read_lock_bh(); > + irq_rt = rcu_dereference(kvm->irq_routing); > + if (irq < irq_rt->nr_rt_entries) > + hlist_for_each_entry(e, n, &irq_rt->map[irq], link) { > + if (ei->type == KVM_IRQ_ROUTING_MSI) > + ret = kvm_set_msi(e, kvm, irq_source_id, level, > + host_irq); > + else > + ret = -EWOULDBLOCK; > + break; > + } > + rcu_read_unlock_bh(); > + return ret; > +} > + > void kvm_notify_acked_irq(struct kvm *kvm, unsigned irqchip, unsigned pin) > { > struct kvm_irq_ack_notifier *kian; Highly welcome feature! Jan -- Siemens AG, Corporate Technology, CT T DE IT 1 Corporate Competence Center Embedded Linux