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Subject[87/98] KVM: only allow one gsi per fd
2.6.32-stable review patch.  If anyone has any objections, please let us know.

------------------

From: Michael S. Tsirkin <mst@redhat.com>

commit f1d1c309f35e9b0fb961cffd70fbd04f450ec47c upstream.

Looks like repeatedly binding same fd to multiple gsi's with irqfd can
use up a ton of kernel memory for irqfd structures.

A simple fix is to allow each fd to only trigger one gsi: triggering a
storm of interrupts in guest is likely useless anyway, and we can do it
by binding a single gsi to many interrupts if we really want to.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Acked-by: Acked-by: Gregory Haskins <ghaskins@novell.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
virt/kvm/eventfd.c | 15 +++++++++++++--
1 file changed, 13 insertions(+), 2 deletions(-)

--- a/virt/kvm/eventfd.c
+++ b/virt/kvm/eventfd.c
@@ -168,7 +168,7 @@ irqfd_ptable_queue_proc(struct file *fil
static int
kvm_irqfd_assign(struct kvm *kvm, int fd, int gsi)
{
- struct _irqfd *irqfd;
+ struct _irqfd *irqfd, *tmp;
struct file *file = NULL;
struct eventfd_ctx *eventfd = NULL;
int ret;
@@ -205,9 +205,20 @@ kvm_irqfd_assign(struct kvm *kvm, int fd
init_waitqueue_func_entry(&irqfd->wait, irqfd_wakeup);
init_poll_funcptr(&irqfd->pt, irqfd_ptable_queue_proc);

+ spin_lock_irq(&kvm->irqfds.lock);
+
+ ret = 0;
+ list_for_each_entry(tmp, &kvm->irqfds.items, list) {
+ if (irqfd->eventfd != tmp->eventfd)
+ continue;
+ /* This fd is used for another irq already. */
+ ret = -EBUSY;
+ spin_unlock_irq(&kvm->irqfds.lock);
+ goto fail;
+ }
+
events = file->f_op->poll(file, &irqfd->pt);

- spin_lock_irq(&kvm->irqfds.lock);
list_add_tail(&irqfd->list, &kvm->irqfds.items);
spin_unlock_irq(&kvm->irqfds.lock);




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