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Message-Id: <20210624181356.10235-3-peterx@redhat.com>
Date: Thu, 24 Jun 2021 14:13:49 -0400
From: Peter Xu <peterx@...hat.com>
To: kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Cc: Paolo Bonzini <pbonzini@...hat.com>,
Vitaly Kuznetsov <vkuznets@...hat.com>,
Maxim Levitsky <mlevitsk@...hat.com>, peterx@...hat.com,
Sean Christopherson <seanjc@...gle.com>
Subject: [PATCH 2/9] KVM: Introduce kvm_get_kvm_safe()
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@...hat.com>
---
include/linux/kvm_host.h | 1 +
virt/kvm/kvm_main.c | 17 +++++++++++------
2 files changed, 12 insertions(+), 6 deletions(-)
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 2f34487e21f2..53d7d09eebd7 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -698,6 +698,7 @@ int kvm_init(void *opaque, unsigned vcpu_size, unsigned vcpu_align,
void kvm_exit(void);
void kvm_get_kvm(struct kvm *kvm);
+bool kvm_get_kvm_safe(struct kvm *kvm);
void kvm_put_kvm(struct kvm *kvm);
bool file_is_kvm(struct file *file);
void kvm_put_kvm_no_destroy(struct kvm *kvm);
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index d170f65e15b0..0b4f55370b18 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -1049,6 +1049,16 @@ void kvm_get_kvm(struct kvm *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)
{
if (refcount_dec_and_test(&kvm->users_count))
@@ -4713,12 +4723,7 @@ static int kvm_debugfs_open(struct inode *inode, struct file *file,
struct kvm_stat_data *stat_data = (struct kvm_stat_data *)
inode->i_private;
- /* The debugfs files are a reference to the kvm struct which
- * is still valid when kvm_destroy_vm is called.
- * To avoid the race between open and the removal of the debugfs
- * directory we test against the users count.
- */
- if (!refcount_inc_not_zero(&stat_data->kvm->users_count))
+ if (!kvm_get_kvm_safe(stat_data->kvm))
return -ENOENT;
if (simple_attr_open(inode, file, get,
--
2.31.1
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