KVM: irqfd

KVM provides a complete virtual system environment for guests, including
support for injecting interrupts modeled after the real exception/interrupt
facilities present on the native platform (such as the IDT on x86).
Virtual interrupts can come from a variety of sources (emulated devices,
pass-through devices, etc) but all must be injected to the guest via
the KVM infrastructure.  This patch adds a new mechanism to inject a specific
interrupt to a guest using a decoupled eventfd mechnanism:  Any legal signal
on the irqfd (using eventfd semantics from either userspace or kernel) will
translate into an injected interrupt in the guest at the next available
interrupt window.

Signed-off-by: Gregory Haskins <ghaskins@novell.com>
Signed-off-by: Avi Kivity <avi@redhat.com>

2 files changed, 35 insertions, 0 deletions

diff --git a/include/linux/kvm.h b/include/linux/kvm.h
index 7b17141c47c9..8f53f24e5274 100644
--- a/include/linux/kvm.h
+++ b/include/linux/kvm.h
@@ -418,6 +418,7 @@ struct kvm_trace_rec {
 #ifdef __KVM_HAVE_MCE
 #define KVM_CAP_MCE 31
 #endif
+#define KVM_CAP_IRQFD 32
 
 #ifdef KVM_CAP_IRQ_ROUTING
 
@@ -470,6 +471,15 @@ struct kvm_x86_mce {
 };
 #endif
 
+#define KVM_IRQFD_FLAG_DEASSIGN (1 << 0)
+
+struct kvm_irqfd {
+        __u32 fd;
+        __u32 gsi;
+        __u32 flags;
+        __u8  pad[20];
+};
+
 /*
  * ioctls for VM fds
  */
@@ -514,6 +524,7 @@ struct kvm_x86_mce {
 #define KVM_ASSIGN_SET_MSIX_ENTRY \
                         _IOW(KVMIO, 0x74, struct kvm_assigned_msix_entry)
 #define KVM_DEASSIGN_DEV_IRQ       _IOW(KVMIO, 0x75, struct kvm_assigned_irq)
+#define KVM_IRQFD                  _IOW(KVMIO, 0x76, struct kvm_irqfd)
 
 /*
  * ioctls for vcpu fds
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 3060bdc35ffe..7724dcb6ff76 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -136,6 +136,12 @@ struct kvm {
         struct list_head vm_list;
         struct kvm_io_bus mmio_bus;
         struct kvm_io_bus pio_bus;
+#ifdef CONFIG_HAVE_KVM_EVENTFD
+        struct {
+                spinlock_t        lock;
+                struct list_head  items;
+        } irqfds;
+#endif
         struct kvm_vm_stat stat;
         struct kvm_arch arch;
         atomic_t users_count;
@@ -525,4 +531,22 @@ static inline void kvm_free_irq_routing(struct kvm *kvm) {}
 
 #endif
 
+#ifdef CONFIG_HAVE_KVM_EVENTFD
+
+void kvm_irqfd_init(struct kvm *kvm);
+int kvm_irqfd(struct kvm *kvm, int fd, int gsi, int flags);
+void kvm_irqfd_release(struct kvm *kvm);
+
+#else
+
+static inline void kvm_irqfd_init(struct kvm *kvm) {}
+static inline int kvm_irqfd(struct kvm *kvm, int fd, int gsi, int flags)
+{
+        return -EINVAL;
+}
+
+static inline void kvm_irqfd_release(struct kvm *kvm) {}
+
+#endif /* CONFIG_HAVE_KVM_EVENTFD */
+
 #endif