[PATCH v3] qemu-kvm: add iosignalfd support

[Gregory Haskins <ghaskins@novell.com>]

An iosignalfd allows an eventfd to attach to a specific PIO/MMIO region in the
guest.  Any guest-writes to that region will trigger an eventfd signal.

[
  This userspace patch coorelates to the kvm.git patches, v5, which you
  can find here: http://lkml.org/lkml/2009/6/3/433, and are based on top
  of the irqfd userspace patches which have not yet been accepted upstream.
]

Signed-off-by: Gregory Haskins <ghaskins@novell.com>
---

 kvm/libkvm/libkvm.c |   68 +++++++++++++++++++++++++++++++++++++++++++++++++++
 kvm/libkvm/libkvm.h |   42 ++++++++++++++++++++++++++++++++
 2 files changed, 110 insertions(+), 0 deletions(-)

diff --git a/kvm/libkvm/libkvm.c b/kvm/libkvm/libkvm.c
index 0ada15c..cb558fc 100644
--- a/kvm/libkvm/libkvm.c
+++ b/kvm/libkvm/libkvm.c
@@ -1493,3 +1493,71 @@ int kvm_irqfd(kvm_context_t kvm, int gsi, int flags)
 }
 
 #endif /* KVM_CAP_IRQFD */
+
+#ifdef KVM_CAP_IOSIGNALFD
+
+#include <sys/eventfd.h>
+
+int kvm_assign_iosignalfd(kvm_context_t kvm, unsigned long addr, size_t len,
+			  int fd, void *trigger, int flags)
+{
+	int r;
+	int type = flags & IOSIGNALFD_FLAG_PIO; 
+	struct kvm_iosignalfd data = {
+		.trigger = (__u64)trigger,
+		.addr    = addr,
+		.len     = len,
+		.fd      = fd,
+	};
+
+	data.flags |= trigger ? KVM_IOSIGNALFD_FLAG_TRIGGER : 0;
+	data.flags |= type ? KVM_IOSIGNALFD_FLAG_PIO : 0;
+
+	if (!kvm_check_extension(kvm, KVM_CAP_IOSIGNALFD))
+		return -ENOENT;
+
+	r = ioctl(kvm->vm_fd, KVM_IOSIGNALFD, &data);
+	if (r == -1)
+		r = -errno;
+	return r;
+}
+
+int kvm_deassign_iosignalfd(kvm_context_t kvm, unsigned long addr, int fd,
+			    int flags)
+{
+	int r;
+	int type = flags & IOSIGNALFD_FLAG_PIO; 
+	struct kvm_iosignalfd data = {
+		.addr    = addr,
+		.fd      = fd,
+		.flags   = KVM_IOSIGNALFD_FLAG_DEASSIGN |
+		(type ? KVM_IOSIGNALFD_FLAG_PIO : 0),
+	};
+
+	if (!kvm_check_extension(kvm, KVM_CAP_IOSIGNALFD))
+		return -ENOENT;
+
+	r = ioctl(kvm->vm_fd, KVM_IOSIGNALFD, &data);
+	if (r == -1)
+		r = -errno;
+	return r;
+}
+
+#else /* KVM_CAP_IOSIGNALFD */
+
+int kvm_assign_iosignalfd(kvm_context_t kvm, unsigned long addr, size_t len,
+			  int fd, void *trigger, int flags)
+{
+	return -ENOSYS;
+}
+
+int kvm_deassign_iosignalfd(kvm_context_t kvm, unsigned long addr, int fd,
+			    int flags)
+{
+	return -ENOSYS;
+}
+
+#endif /* KVM_CAP_IOSIGNALFD */
+
+
+
diff --git a/kvm/libkvm/libkvm.h b/kvm/libkvm/libkvm.h
index aca8ed6..65fbe2a 100644
--- a/kvm/libkvm/libkvm.h
+++ b/kvm/libkvm/libkvm.h
@@ -870,6 +870,48 @@ int kvm_get_irq_route_gsi(kvm_context_t kvm);
  */
 int kvm_irqfd(kvm_context_t kvm, int gsi, int flags);
 
+enum {
+	iosignalfd_option_pio,
+};
+
+#define IOSIGNALFD_FLAG_PIO    (1 << iosignalfd_option_pio)
+
+/*!
+ * \brief Assign an eventfd to an IO port (PIO or MMIO)
+ *
+ * Assigns an eventfd based file-descriptor to a specific PIO or MMIO
+ * address range.  Any guest writes to the specified range will generate
+ * an eventfd signal.
+ *
+ * A data-match pointer can be optionally provided in "trigger" and only
+ * writes which match this value exactly will generate an event.  The length
+ * of the trigger is established by the length of the overall IO range, and
+ * therefore must be in a natural byte-width for the IO routines of your
+ * particular architecture (e.g. 1, 2, 4, or 8 bytes on x86_64).
+ *
+ * \param kvm Pointer to the current kvm_context
+ * \param addr The IO address
+ * \param len The length of the IO region at the address
+ * \param fd The eventfd file-descriptor
+ * \param trigger A optional pointer providing data-match token
+ * \param flags FLAG_PIO: PIO, else MMIO
+ */
+int kvm_assign_iosignalfd(kvm_context_t kvm, unsigned long addr, size_t len,
+			  int fd, void *trigger, int flags);
+
+/*!
+ * \brief Deassign an iosignalfd from a previously registered IO port
+ *
+ * Deassigns an iosignalfd previously registered with kvm_assign_iosignalfd()
+ *
+ * \param kvm Pointer to the current kvm_context
+ * \param addr The IO address to deassign
+ * \param fd The eventfd file-descriptor
+ * \param flags FLAG_PIO: PIO, else MMIO
+ */
+int kvm_deassign_iosignalfd(kvm_context_t kvm, unsigned long addr,
+			    int fd, int flags);
+
 #ifdef KVM_CAP_DEVICE_MSIX
 int kvm_assign_set_msix_nr(kvm_context_t kvm,
 			   struct kvm_assigned_msix_nr *msix_nr);