kvm: exclude ioeventfd from counting kvm_io_range limit (6ea34c9b) · Commits · 戴 / test

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>

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)

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