kvm: exclude ioeventfd from counting kvm_io_range limit

We can easily reach the 1000 limit by start VM with a couple
hundred I/O devices (multifunction=on). The hardcode limit
already been adjusted 3 times (6 ~ 200 ~ 300 ~ 1000).

In userspace, we already have maximum file descriptor to
limit ioeventfd count. But kvm_io_bus devices also are used
for pit, pic, ioapic, coalesced_mmio. They couldn't be limited
by maximum file descriptor.

Currently only ioeventfds take too much kvm_io_bus devices,
so just exclude it from counting kvm_io_range limit.

Also fixed one indent issue in kvm_host.h

Signed-off-by: Amos Kong <akong@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Gleb Natapov <gleb@redhat.com>

1 files changed, 2 insertions, 1 deletions

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index b547a1ceecbc..1580dd4ace4e 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -2926,7 +2926,8 @@ int kvm_io_bus_register_dev(struct kvm *kvm, enum kvm_bus bus_idx, gpa_t addr,
         struct kvm_io_bus *new_bus, *bus;
 
         bus = kvm->buses[bus_idx];
-        if (bus->dev_count > NR_IOBUS_DEVS - 1)
+        /* exclude ioeventfd which is limited by maximum fd */
+        if (bus->dev_count - bus->ioeventfd_count > NR_IOBUS_DEVS - 1)
                 return -ENOSPC;
 
         new_bus = kzalloc(sizeof(*bus) + ((bus->dev_count + 1) *