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KVM: add vm refcounting

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the main purpose of adding this functions is the abilaty to release the
spinlock that protect the kvm list while still be able to do operations
on a specific kvm in a safe way.

Signed-off-by: Izik Eidus <izike@qumranet.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>
This commit is contained in:
Izik Eidus 2008-03-30 16:01:25 +03:00 committed by Avi Kivity
parent 9c20456a32
commit d39f13b0da
2 changed files with 20 additions and 1 deletions
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4
include/linux/kvm_host.h
View file

@ -114,6 +114,7 @@ struct kvm {
struct kvm_io_bus pio_bus;
struct kvm_vm_stat stat;
struct kvm_arch arch;
atomic_t users_count;
};
/* The guest did something we don't support. */
@ -140,6 +141,9 @@ int kvm_init(void *opaque, unsigned int vcpu_size,
struct module *module);
void kvm_exit(void);
void kvm_get_kvm(struct kvm *kvm);
void kvm_put_kvm(struct kvm *kvm);
#define HPA_MSB ((sizeof(hpa_t) * 8) - 1)
#define HPA_ERR_MASK ((hpa_t)1 << HPA_MSB)
static inline int is_error_hpa(hpa_t hpa) { return hpa >> HPA_MSB; }

17
virt/kvm/kvm_main.c
View file

@ -193,6 +193,7 @@ static struct kvm *kvm_create_vm(void)
mutex_init(&kvm->lock);
kvm_io_bus_init(&kvm->mmio_bus);
init_rwsem(&kvm->slots_lock);
atomic_set(&kvm->users_count, 1);
spin_lock(&kvm_lock);
list_add(&kvm->vm_list, &vm_list);
spin_unlock(&kvm_lock);
@ -242,11 +243,25 @@ static void kvm_destroy_vm(struct kvm *kvm)
mmdrop(mm);
}
void kvm_get_kvm(struct kvm *kvm)
{
atomic_inc(&kvm->users_count);
}
EXPORT_SYMBOL_GPL(kvm_get_kvm);
void kvm_put_kvm(struct kvm *kvm)
{
if (atomic_dec_and_test(&kvm->users_count))
kvm_destroy_vm(kvm);
}
EXPORT_SYMBOL_GPL(kvm_put_kvm);
static int kvm_vm_release(struct inode *inode, struct file *filp)
{
struct kvm *kvm = filp->private_data;
kvm_destroy_vm(kvm);
kvm_put_kvm(kvm);
return 0;
}