DEASSIGN allows us to optionally disassociate an IRQFD from its underlying
eventfd without destroying the eventfd in the process. This is useful
for conditions like live-migration which may have an eventfd associated
with a device and an IRQFD. We need to be able to decouple the guest
from the event source while not perturbing the event source itself.
Signed-off-by: Gregory Haskins <ghaskins@xxxxxxxxxx>
CC: Michael S. Tsirkin <mst@xxxxxxxxxx>
---
include/linux/kvm.h | 2 ++
virt/kvm/eventfd.c | 46 ++++++++++++++++++++++++++++++++++++++++++++--
2 files changed, 46 insertions(+), 2 deletions(-)
diff --git a/include/linux/kvm.h b/include/linux/kvm.h
index 69d3d73..76c6408 100644
--- a/include/linux/kvm.h
+++ b/include/linux/kvm.h
@@ -461,6 +461,8 @@ struct kvm_x86_mce {
};
#endif
+#define KVM_IRQFD_FLAG_DEASSIGN (1 << 0)
+
struct kvm_irqfd {
__u32 fd;
__u32 gsi;
diff --git a/virt/kvm/eventfd.c b/virt/kvm/eventfd.c
index 05ce447..0fd200c 100644
--- a/virt/kvm/eventfd.c
+++ b/virt/kvm/eventfd.c
@@ -161,8 +161,8 @@ irqfd_ptable_queue_proc(struct file *file, wait_queue_head_t *wqh,
add_wait_queue(wqh, &irqfd->wait);
}
-int
-kvm_irqfd(struct kvm *kvm, int fd, int gsi, int flags)
+static int
+kvm_irqfd_assign(struct kvm *kvm, int fd, int gsi)
{
struct _irqfd *irqfd;
struct file *file = NULL;
@@ -241,6 +241,48 @@ kvm_irqfd_init(struct kvm *kvm)
}
/*
+ * shutdown any irqfd's that match fd+gsi
+ */
+static int
+kvm_irqfd_deassign(struct kvm *kvm, int fd, int gsi)
+{
+ struct _irqfd *irqfd, *tmp;
+ struct eventfd_ctx *eventfd;
+
+ eventfd = eventfd_ctx_fdget(fd);
+ if (IS_ERR(eventfd))
+ return PTR_ERR(eventfd);
+
+ spin_lock_irq(&kvm->irqfds.lock);
+
+ list_for_each_entry_safe(irqfd, tmp, &kvm->irqfds.items, list) {
+ if (irqfd->eventfd == eventfd && irqfd->gsi == gsi)
+ irqfd_deactivate(irqfd);
+ }
+
+ spin_unlock_irq(&kvm->irqfds.lock);
+ eventfd_ctx_put(eventfd);
+
+ /*
+ * Block until we know all outstanding shutdown jobs have completed
+ * so that we guarantee there will not be any more interrupts on this
+ * gsi once this deassign function returns.
+ */
+ flush_workqueue(irqfd_cleanup_wq);
+
+ return 0;
+}
+
+int
+kvm_irqfd(struct kvm *kvm, int fd, int gsi, int flags)
+{
+ if (flags & KVM_IRQFD_FLAG_DEASSIGN)
+ return kvm_irqfd_deassign(kvm, fd, gsi);
+
+ return kvm_irqfd_assign(kvm, fd, gsi);
+}
+
+/*
* This function is called as the kvm VM fd is being released. Shutdown all
* irqfds that still remain open
*/
--
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