From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: vballoon: page allocation failure. order:0 -> Kernel panic Date: Tue, 24 Feb 2009 14:28:08 +0200 Message-ID: <49A3E7D8.4060108@redhat.com> References: <49A3DC82.2030704@wpkg.org> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: "kvm@vger.kernel.org" To: Tomasz Chmielewski Return-path: Received: from mx2.redhat.com ([66.187.237.31]:36326 "EHLO mx2.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752925AbZBXM2N (ORCPT ); Tue, 24 Feb 2009 07:28:13 -0500 In-Reply-To: <49A3DC82.2030704@wpkg.org> Sender: kvm-owner@vger.kernel.org List-ID: Tomasz Chmielewski wrote: > I'm trying to use ballooning with kvm-83. > > Although I'm able to limit the guest's memory, when I try to increase > it right after that, I get "vballoon: page allocation failure. > order:0" followed by a kernel panic. > > Is it expected? > > The guest is running Debian Lenny with 2.6.26 kernel. It had initially > 256 MB memory. > It's a guest bug, fixed in 2.6.27 by commit 532a6086e35fa3b5761e68af36d4e42a550eba15 Author: Anthony Liguori Date: Mon Aug 18 17:15:31 2008 -0500 virtio_balloon: fix towards_target when deflating balloon Both v and vb->num_pages are u32 and unsigned int respectively. If v is less than vb->num_pages (and it is, when deflating the balloon), the result is a very large 32-bit number. Since we're returning a s64, instead of getting the same negative number we desire, we get a very large positive number. This handles the case where v < vb->num_pages and ensures we get a small, negative, s64 as the result. Rusty: please push this for 2.6.27-rc4. It's probably appropriate for the stable tree too as it will cause an unexpected OOM when ballooning. Signed-off-by: Anthony Liguori Signed-off-by: Rusty Russell (simplified) diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c index bfef604..62eab43 100644 --- a/drivers/virtio/virtio_balloon.c +++ b/drivers/virtio/virtio_balloon.c @@ -158,7 +158,7 @@ static inline s64 towards_target(struct virtio_balloon *vb) vb->vdev->config->get(vb->vdev, offsetof(struct virtio_balloon_config, num_pages), &v, sizeof(v)); - return v - vb->num_pages; + return (s64)v - vb->num_pages; } static void update_balloon_size(struct virtio_balloon *vb) -- error compiling committee.c: too many arguments to function