[PATCH] xen/xenbus: Don't leak memory when unmapping the ring on HVM backend

[PATCH] xen/xenbus: Don't leak memory when unmapping the ring on HVM backend

[Julien Grall]

The commit ccc9d90a9a8b5c4ad7e9708ec41f75ff9e98d61d "xenbus_client:
Extend interface to support multi-page ring" removes the call to
free_xenballooned_pages in xenbus_unmap_ring_vfree_hvm.

This will result to not give back the pages to Linux and loose them
forever. It only happens when the backends are running in HVM domains.

Signed-off-by: Julien Grall <julien.grall@citrix.com>

---
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: David Vrabel <david.vrabel@citrix.com>
Cc: Wei Liu <wei.liu2@citrix.com>

Appeared in Linux 4.1. HVM backend, which is always the case on ARM, will
leak every mapped ring (i.e ~12KB per domain with 1 disk and 1 vif).
---
 drivers/xen/xenbus/xenbus_client.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/xen/xenbus/xenbus_client.c b/drivers/xen/xenbus/xenbus_client.c
index 9ad3272..e303535 100644
--- a/drivers/xen/xenbus/xenbus_client.c
+++ b/drivers/xen/xenbus/xenbus_client.c
@@ -814,8 +814,10 @@ static int xenbus_unmap_ring_vfree_hvm(struct xenbus_device *dev, void *vaddr)
 
 	rv = xenbus_unmap_ring(dev, node->handles, node->nr_handles,
 			       addrs);
-	if (!rv)
+	if (!rv) {
 		vunmap(vaddr);
+		free_xenballooned_pages(node->nr_handles, node->hvm.pages);
+	}
 	else
 		WARN(1, "Leaking %p, size %u page(s)\n", vaddr,
 		     node->nr_handles);
-- 
2.1.4

Re: [PATCH] xen/xenbus: Don't leak memory when unmapping the ring on HVM backend

[Boris Ostrovsky]

On 08/10/2015 02:10 PM, Julien Grall wrote:
> The commit ccc9d90a9a8b5c4ad7e9708ec41f75ff9e98d61d "xenbus_client:
> Extend interface to support multi-page ring" removes the call to
> free_xenballooned_pages in xenbus_unmap_ring_vfree_hvm.
>
> This will result to not give back the pages to Linux and loose them
> forever. It only happens when the backends are running in HVM domains.
>
> Signed-off-by: Julien Grall <julien.grall@citrix.com>

Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>

>
> ---
> Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
> Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
> Cc: David Vrabel <david.vrabel@citrix.com>
> Cc: Wei Liu <wei.liu2@citrix.com>
>
> Appeared in Linux 4.1. HVM backend, which is always the case on ARM, will
> leak every mapped ring (i.e ~12KB per domain with 1 disk and 1 vif).
> ---
>   drivers/xen/xenbus/xenbus_client.c | 4 +++-
>   1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/xen/xenbus/xenbus_client.c b/drivers/xen/xenbus/xenbus_client.c
> index 9ad3272..e303535 100644
> --- a/drivers/xen/xenbus/xenbus_client.c
> +++ b/drivers/xen/xenbus/xenbus_client.c
> @@ -814,8 +814,10 @@ static int xenbus_unmap_ring_vfree_hvm(struct xenbus_device *dev, void *vaddr)
>   
>   	rv = xenbus_unmap_ring(dev, node->handles, node->nr_handles,
>   			       addrs);
> -	if (!rv)
> +	if (!rv) {
>   		vunmap(vaddr);
> +		free_xenballooned_pages(node->nr_handles, node->hvm.pages);
> +	}
>   	else
>   		WARN(1, "Leaking %p, size %u page(s)\n", vaddr,
>   		     node->nr_handles);

Re: [PATCH] xen/xenbus: Don't leak memory when unmapping the ring on HVM backend

[Wei Liu]

On Mon, Aug 10, 2015 at 07:10:38PM +0100, Julien Grall wrote:
> The commit ccc9d90a9a8b5c4ad7e9708ec41f75ff9e98d61d "xenbus_client:
> Extend interface to support multi-page ring" removes the call to
> free_xenballooned_pages in xenbus_unmap_ring_vfree_hvm.
> 
> This will result to not give back the pages to Linux and loose them
> forever. It only happens when the backends are running in HVM domains.
> 
> Signed-off-by: Julien Grall <julien.grall@citrix.com>
> 
> ---
> Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
> Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
> Cc: David Vrabel <david.vrabel@citrix.com>
> Cc: Wei Liu <wei.liu2@citrix.com>
> 

Reviewed-by: Wei Liu <wei.liu2@citrix.com>

> Appeared in Linux 4.1. HVM backend, which is always the case on ARM, will
> leak every mapped ring (i.e ~12KB per domain with 1 disk and 1 vif).
> ---
>  drivers/xen/xenbus/xenbus_client.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/xen/xenbus/xenbus_client.c b/drivers/xen/xenbus/xenbus_client.c
> index 9ad3272..e303535 100644
> --- a/drivers/xen/xenbus/xenbus_client.c
> +++ b/drivers/xen/xenbus/xenbus_client.c
> @@ -814,8 +814,10 @@ static int xenbus_unmap_ring_vfree_hvm(struct xenbus_device *dev, void *vaddr)
>  
>  	rv = xenbus_unmap_ring(dev, node->handles, node->nr_handles,
>  			       addrs);
> -	if (!rv)
> +	if (!rv) {
>  		vunmap(vaddr);
> +		free_xenballooned_pages(node->nr_handles, node->hvm.pages);
> +	}
>  	else
>  		WARN(1, "Leaking %p, size %u page(s)\n", vaddr,
>  		     node->nr_handles);
> -- 
> 2.1.4

Re: [Xen-devel] [PATCH] xen/xenbus: Don't leak memory when unmapping the ring on HVM backend

[David Vrabel]

On 10/08/15 19:10, Julien Grall wrote:
> The commit ccc9d90a9a8b5c4ad7e9708ec41f75ff9e98d61d "xenbus_client:
> Extend interface to support multi-page ring" removes the call to
> free_xenballooned_pages in xenbus_unmap_ring_vfree_hvm.
> 
> This will result to not give back the pages to Linux and loose them
> forever. It only happens when the backends are running in HVM domains.

Applied to for-linus-4.2 and tagged for stable, thanks.

David