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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>
This commit is contained in:
Amos Kong 2013-05-25 06:44:15 +08:00 committed by Gleb Natapov
parent 566af9404b
commit 6ea34c9b78
3 changed files with 6 additions and 2 deletions
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3
include/linux/kvm_host.h
View File

@ -145,7 +145,8 @@ struct kvm_io_range {
#define NR_IOBUS_DEVS 1000 #define NR_IOBUS_DEVS 1000
struct kvm_io_bus { struct kvm_io_bus {
int dev_count; int dev_count;
int ioeventfd_count;
struct kvm_io_range range[]; struct kvm_io_range range[];
}; };

2
virt/kvm/eventfd.c
View File

@ -753,6 +753,7 @@ kvm_assign_ioeventfd(struct kvm *kvm, struct kvm_ioeventfd *args)
if (ret < 0) if (ret < 0)
goto unlock_fail; goto unlock_fail;
kvm->buses[bus_idx]->ioeventfd_count++;
list_add_tail(&p->list, &kvm->ioeventfds); list_add_tail(&p->list, &kvm->ioeventfds);
mutex_unlock(&kvm->slots_lock); mutex_unlock(&kvm->slots_lock);
@ -798,6 +799,7 @@ kvm_deassign_ioeventfd(struct kvm *kvm, struct kvm_ioeventfd *args)
continue; continue;
kvm_io_bus_unregister_dev(kvm, bus_idx, &p->dev); kvm_io_bus_unregister_dev(kvm, bus_idx, &p->dev);
kvm->buses[bus_idx]->ioeventfd_count--;
ioeventfd_release(p); ioeventfd_release(p);
ret = 0; ret = 0;
break; break;

3
virt/kvm/kvm_main.c
View File

@ -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; struct kvm_io_bus *new_bus, *bus;
bus = kvm->buses[bus_idx]; 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; return -ENOSPC;
new_bus = kzalloc(sizeof(*bus) + ((bus->dev_count + 1) * new_bus = kzalloc(sizeof(*bus) + ((bus->dev_count + 1) *