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Commit 6ea34c9b authored by Amos Kong's avatar Amos Kong Committed by Gleb Natapov
Browse files

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: default avatarAmos Kong <akong@redhat.com>
Reviewed-by: default avatarStefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: default avatarGleb Natapov <gleb@redhat.com>
parent 566af940

include/linux/kvm_host.h

+2 −1
Original line number Diff line number Diff line
@@ -146,6 +146,7 @@ struct kvm_io_range { 


struct kvm_io_bus {

	int dev_count;

	int ioeventfd_count;

	struct kvm_io_range range[];

};

virt/kvm/eventfd.c

+2 −0
Original line number Diff line number Diff line
@@ -753,6 +753,7 @@ kvm_assign_ioeventfd(struct kvm *kvm, struct kvm_ioeventfd *args) 
	if (ret < 0)

		goto unlock_fail;



	kvm->buses[bus_idx]->ioeventfd_count++;

	list_add_tail(&p->list, &kvm->ioeventfds);



	mutex_unlock(&kvm->slots_lock);
@@ -798,6 +799,7 @@ kvm_deassign_ioeventfd(struct kvm *kvm, struct kvm_ioeventfd *args) 
			continue;



		kvm_io_bus_unregister_dev(kvm, bus_idx, &p->dev);

		kvm->buses[bus_idx]->ioeventfd_count--;

		ioeventfd_release(p);

		ret = 0;

		break;

virt/kvm/kvm_main.c

+2 −1
Original line number Diff line number Diff line
@@ -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) *