kvm: add kvm_set_irq_inatomic

Add an API to inject IRQ from atomic context.
Return EWOULDBLOCK if impossible (e.g. for multicast).
Only MSI is supported ATM.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Gleb Natapov <gleb@redhat.com>

diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 8e5c7b6..36c3704 100644 (file)
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -693,6 +693,7 @@ void kvm_get_intr_delivery_bitmask(struct kvm_ioapic *ioapic,
                                   unsigned long *deliver_bitmask);
 #endif
 int kvm_set_irq(struct kvm *kvm, int irq_source_id, u32 irq, int level);
+int kvm_set_irq_inatomic(struct kvm *kvm, int irq_source_id, u32 irq, int level);
 int kvm_set_msi(struct kvm_kernel_irq_routing_entry *irq_entry, struct kvm *kvm,
                int irq_source_id, int level);
 void kvm_notify_acked_irq(struct kvm *kvm, unsigned irqchip, unsigned pin);

diff --git a/virt/kvm/irq_comm.c b/virt/kvm/irq_comm.c
index 2eb58af..656fa45 100644 (file)
--- a/virt/kvm/irq_comm.c
+++ b/virt/kvm/irq_comm.c
@@ -102,6 +102,23 @@ int kvm_irq_delivery_to_apic(struct kvm *kvm, struct kvm_lapic *src,
        return r;
 }
 
+static inline void kvm_set_msi_irq(struct kvm_kernel_irq_routing_entry *e,
+                                  struct kvm_lapic_irq *irq)
+{
+       trace_kvm_msi_set_irq(e->msi.address_lo, e->msi.data);
+
+       irq->dest_id = (e->msi.address_lo &
+                       MSI_ADDR_DEST_ID_MASK) >> MSI_ADDR_DEST_ID_SHIFT;
+       irq->vector = (e->msi.data &
+                       MSI_DATA_VECTOR_MASK) >> MSI_DATA_VECTOR_SHIFT;
+       irq->dest_mode = (1 << MSI_ADDR_DEST_MODE_SHIFT) & e->msi.address_lo;
+       irq->trig_mode = (1 << MSI_DATA_TRIGGER_SHIFT) & e->msi.data;
+       irq->delivery_mode = e->msi.data & 0x700;
+       irq->level = 1;
+       irq->shorthand = 0;
+       /* TODO Deal with RH bit of MSI message address */
+}
+
 int kvm_set_msi(struct kvm_kernel_irq_routing_entry *e,
                struct kvm *kvm, int irq_source_id, int level)
 {
@@ -110,22 +127,26 @@ int kvm_set_msi(struct kvm_kernel_irq_routing_entry *e,
        if (!level)
                return -1;
 
-       trace_kvm_msi_set_irq(e->msi.address_lo, e->msi.data);
+       kvm_set_msi_irq(e, &irq);
 
-       irq.dest_id = (e->msi.address_lo &
-                       MSI_ADDR_DEST_ID_MASK) >> MSI_ADDR_DEST_ID_SHIFT;
-       irq.vector = (e->msi.data &
-                       MSI_DATA_VECTOR_MASK) >> MSI_DATA_VECTOR_SHIFT;
-       irq.dest_mode = (1 << MSI_ADDR_DEST_MODE_SHIFT) & e->msi.address_lo;
-       irq.trig_mode = (1 << MSI_DATA_TRIGGER_SHIFT) & e->msi.data;
-       irq.delivery_mode = e->msi.data & 0x700;
-       irq.level = 1;
-       irq.shorthand = 0;
-
-       /* TODO Deal with RH bit of MSI message address */
        return kvm_irq_delivery_to_apic(kvm, NULL, &irq);
 }
 
+
+static int kvm_set_msi_inatomic(struct kvm_kernel_irq_routing_entry *e,
+                        struct kvm *kvm)
+{
+       struct kvm_lapic_irq irq;
+       int r;
+
+       kvm_set_msi_irq(e, &irq);
+
+       if (kvm_irq_delivery_to_apic_fast(kvm, NULL, &irq, &r))
+               return r;
+       else
+               return -EWOULDBLOCK;
+}
+
 int kvm_send_userspace_msi(struct kvm *kvm, struct kvm_msi *msi)
 {
        struct kvm_kernel_irq_routing_entry route;
@@ -178,6 +199,44 @@ int kvm_set_irq(struct kvm *kvm, int irq_source_id, u32 irq, int level)
        return ret;
 }
 
+/*
+ * 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: retry in a process context.
+ *  Other values - No need to retry.
+ */
+int kvm_set_irq_inatomic(struct kvm *kvm, int irq_source_id, u32 irq, int level)
+{
+       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);
+
+       /*
+        * Injection into either PIC or IOAPIC might need to scan all CPUs,
+        * which would need to be retried from thread context;  when same GSI
+        * is connected to both PIC and IOAPIC, we'd have to report a
+        * partial failure here.
+        * Since there's no easy way to do this, we only support injecting MSI
+        * which is limited to 1:1 GSI mapping.
+        */
+       rcu_read_lock();
+       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 (likely(e->type == KVM_IRQ_ROUTING_MSI))
+                               ret = kvm_set_msi_inatomic(e, kvm);
+                       else
+                               ret = -EWOULDBLOCK;
+                       break;
+               }
+       rcu_read_unlock();
+       return ret;
+}
+
 void kvm_notify_acked_irq(struct kvm *kvm, unsigned irqchip, unsigned pin)
 {
        struct kvm_irq_ack_notifier *kian;