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Date: Wed, 18 Jan 2012 20:10:24 +0200
From: "Michael S. Tsirkin" <mst@...hat.com>
To: Alex Williamson <alex.williamson@...hat.com>,
jan.kiszka@...mens.com
Cc: Avi Kivity <avi@...hat.com>, Marcelo Tosatti <mtosatti@...hat.com>,
kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH RFC] kvm: deliver msix interrupts from irq handler
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 <mst@...hat.com>
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;
+}
+
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
+ */
+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;
--
1.7.8.2.325.g247f9
--
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