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>

3 files changed, 3 insertions, 1 deletions

diff --git a/arch/x86/kvm/Kconfig b/arch/x86/kvm/Kconfig
index 939b1cb9c5b3..8cd2a4efe238 100644
--- a/arch/x86/kvm/Kconfig
+++ b/arch/x86/kvm/Kconfig
@@ -26,6 +26,7 @@ config KVM
         select MMU_NOTIFIER
         select ANON_INODES
         select HAVE_KVM_IRQCHIP
+        select HAVE_KVM_EVENTFD
         ---help---
           Support hosting fully virtualized guest machines using hardware
           virtualization extensions.  You will need a fairly recent
diff --git a/arch/x86/kvm/Makefile b/arch/x86/kvm/Makefile
index bee9512cd60d..01e3c61f749a 100644
--- a/arch/x86/kvm/Makefile
+++ b/arch/x86/kvm/Makefile
@@ -2,7 +2,7 @@
 EXTRA_CFLAGS += -Ivirt/kvm -Iarch/x86/kvm
 
 kvm-y                   += $(addprefix ../../../virt/kvm/, kvm_main.o ioapic.o \
-                                coalesced_mmio.o irq_comm.o)
+                                coalesced_mmio.o irq_comm.o eventfd.o)
 kvm-$(CONFIG_KVM_TRACE) += $(addprefix ../../../virt/kvm/, kvm_trace.o)
 kvm-$(CONFIG_IOMMU_API) += $(addprefix ../../../virt/kvm/, iommu.o)
 
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index f0642396783f..15f39fc08ece 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -1126,6 +1126,7 @@ int kvm_dev_ioctl_check_extension(long ext)
         case KVM_CAP_REINJECT_CONTROL:
         case KVM_CAP_IRQ_INJECT_STATUS:
         case KVM_CAP_ASSIGN_DEV_IRQ:
+        case KVM_CAP_IRQFD:
                 r = 1;
                 break;
         case KVM_CAP_COALESCED_MMIO: