[PATCH rework] KVM: coalesced_mmio: fix kvm_coalesced_mmio_init()'s error handling

[PATCH rework] KVM: coalesced_mmio: fix kvm_coalesced_mmio_init()'s error handling

[Takuya Yoshikawa]

kvm_coalesced_mmio_init() keeps to hold the addresses of a coalesced
mmio ring page and dev even after it has freed them.

Also, if this function fails, though it might be rare, it seems to be
suggesting the system's serious state: so we'd better stop the works
following the kvm_creat_vm().

This patch clears these problems.

  We move the coalesced mmio's initialization out of kvm_create_vm().
  This seems to be natural because it includes a registration which
  can be done only when vm is successfully created.

Signed-off-by: Takuya Yoshikawa <yoshikawa.takuya@oss.ntt.co.jp>
---
 virt/kvm/coalesced_mmio.c |    2 ++
 virt/kvm/kvm_main.c       |   12 ++++++++----
 2 files changed, 10 insertions(+), 4 deletions(-)

diff --git a/virt/kvm/coalesced_mmio.c b/virt/kvm/coalesced_mmio.c
index 5169736..11776b7 100644
--- a/virt/kvm/coalesced_mmio.c
+++ b/virt/kvm/coalesced_mmio.c
@@ -119,8 +119,10 @@ int kvm_coalesced_mmio_init(struct kvm *kvm)
 	return ret;
 
 out_free_dev:
+	kvm->coalesced_mmio_dev = NULL;
 	kfree(dev);
 out_free_page:
+	kvm->coalesced_mmio_ring = NULL;
 	__free_page(page);
 out_err:
 	return ret;
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index bcd08b8..c7053aa 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -418,9 +418,6 @@ static struct kvm *kvm_create_vm(void)
 	spin_lock(&kvm_lock);
 	list_add(&kvm->vm_list, &vm_list);
 	spin_unlock(&kvm_lock);
-#ifdef KVM_COALESCED_MMIO_PAGE_OFFSET
-	kvm_coalesced_mmio_init(kvm);
-#endif
 out:
 	return kvm;
 
@@ -1748,12 +1745,19 @@ static struct file_operations kvm_vm_fops = {
 
 static int kvm_dev_ioctl_create_vm(void)
 {
-	int fd;
+	int fd, r;
 	struct kvm *kvm;
 
 	kvm = kvm_create_vm();
 	if (IS_ERR(kvm))
 		return PTR_ERR(kvm);
+#ifdef KVM_COALESCED_MMIO_PAGE_OFFSET
+	r = kvm_coalesced_mmio_init(kvm);
+	if (r < 0) {
+		kvm_put_kvm(kvm);
+		return r;
+	}
+#endif
 	fd = anon_inode_getfd("kvm-vm", &kvm_vm_fops, kvm, O_RDWR);
 	if (fd < 0)
 		kvm_put_kvm(kvm);
-- 
1.6.3.3

Re: [PATCH rework] KVM: coalesced_mmio: fix kvm_coalesced_mmio_init()'s error handling

[Marcelo Tosatti]

On Mon, Mar 15, 2010 at 10:13:30PM +0900, Takuya Yoshikawa wrote:
> kvm_coalesced_mmio_init() keeps to hold the addresses of a coalesced
> mmio ring page and dev even after it has freed them.
> 
> Also, if this function fails, though it might be rare, it seems to be
> suggesting the system's serious state: so we'd better stop the works
> following the kvm_creat_vm().
> 
> This patch clears these problems.
> 
>   We move the coalesced mmio's initialization out of kvm_create_vm().
>   This seems to be natural because it includes a registration which
>   can be done only when vm is successfully created.
> 
> Signed-off-by: Takuya Yoshikawa <yoshikawa.takuya@oss.ntt.co.jp>
> ---
>  virt/kvm/coalesced_mmio.c |    2 ++
>  virt/kvm/kvm_main.c       |   12 ++++++++----
>  2 files changed, 10 insertions(+), 4 deletions(-)

Applied, thanks.