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>

1 files changed, 71 insertions, 12 deletions

diff --git a/virt/kvm/irq_comm.c b/virt/kvm/irq_comm.c
index 2eb58af7ee99..656fa455e154 100644
--- 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;