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KVM: Introduce kvm_get_kvm_safe()

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Introduce this safe version of kvm_get_kvm() so that it can be called even
during vm destruction.  Use it in kvm_debugfs_open() and remove the verbose
comment.  Prepare to be used elsewhere.

Signed-off-by: Peter Xu <peterx@redhat.com>
Message-Id: <20210625153214.43106-3-peterx@redhat.com>
[Preserve the comment in kvm_debugfs_open. - Paolo]
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Peter Xu
2021-06-25 11:32:07 -04:00
committed by Paolo Bonzini
parent 1694caef42
commit 605c713023
2 changed files with 16 additions and 5 deletions
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1
include/linux/kvm_host.h
View File

@@ -755,6 +755,7 @@ int kvm_init(void *opaque, unsigned vcpu_size, unsigned vcpu_align,
void kvm_exit(void); void kvm_exit(void);
void kvm_get_kvm(struct kvm *kvm); void kvm_get_kvm(struct kvm *kvm);
bool kvm_get_kvm_safe(struct kvm *kvm);
void kvm_put_kvm(struct kvm *kvm); void kvm_put_kvm(struct kvm *kvm);
bool file_is_kvm(struct file *file); bool file_is_kvm(struct file *file);
void kvm_put_kvm_no_destroy(struct kvm *kvm); void kvm_put_kvm_no_destroy(struct kvm *kvm);

20
virt/kvm/kvm_main.c
View File

@@ -1120,6 +1120,16 @@ void kvm_get_kvm(struct kvm *kvm)
} }
EXPORT_SYMBOL_GPL(kvm_get_kvm); EXPORT_SYMBOL_GPL(kvm_get_kvm);
/*
* Make sure the vm is not during destruction, which is a safe version of
* kvm_get_kvm(). Return true if kvm referenced successfully, false otherwise.
*/
bool kvm_get_kvm_safe(struct kvm *kvm)
{
return refcount_inc_not_zero(&kvm->users_count);
}
EXPORT_SYMBOL_GPL(kvm_get_kvm_safe);
void kvm_put_kvm(struct kvm *kvm) void kvm_put_kvm(struct kvm *kvm)
{ {
if (refcount_dec_and_test(&kvm->users_count)) if (refcount_dec_and_test(&kvm->users_count))
@@ -4969,12 +4979,12 @@ static int kvm_debugfs_open(struct inode *inode, struct file *file,
struct kvm_stat_data *stat_data = (struct kvm_stat_data *) struct kvm_stat_data *stat_data = (struct kvm_stat_data *)
inode->i_private; inode->i_private;
/* The debugfs files are a reference to the kvm struct which /*
* is still valid when kvm_destroy_vm is called. * The debugfs files are a reference to the kvm struct which
* To avoid the race between open and the removal of the debugfs * is still valid when kvm_destroy_vm is called. kvm_get_kvm_safe
* directory we test against the users count. * avoids the race between open and the removal of the debugfs directory.
*/ */
if (!refcount_inc_not_zero(&stat_data->kvm->users_count)) if (!kvm_get_kvm_safe(stat_data->kvm))
return -ENOENT; return -ENOENT;
if (simple_attr_open(inode, file, get, if (simple_attr_open(inode, file, get,