![Raushaniya Maksudova](/assets/img/avatar_default.png)
Excessive virtio_balloon inflation can cause invocation of OOM-killer, when Linux is under severe memory pressure. Various mechanisms are responsible for correct virtio_balloon memory management. Nevertheless it is often the case that these control tools does not have enough time to react on fast changing memory load. As a result OS runs out of memory and invokes OOM-killer. The balancing of memory by use of the virtio balloon should not cause the termination of processes while there are pages in the balloon. Now there is no way for virtio balloon driver to free some memory at the last moment before some process will be get killed by OOM-killer. This does not provide a security breach as balloon itself is running inside guest OS and is working in the cooperation with the host. Thus some improvements from guest side should be considered as normal. To solve the problem, introduce a virtio_balloon callback which is expected to be called from the oom notifier call chain in out_of_memory() function. If virtio balloon could release some memory, it will make the system to return and retry the allocation that forced the out of memory killer to run. Allocate virtio feature bit for this: it is not set by default, the the guest will not deflate virtio balloon on OOM without explicit permission from host. Signed-off-by: Raushaniya Maksudova <rmaksudova@parallels.com> Signed-off-by: Denis V. Lunev <den@openvz.org> Acked-by: Michael S. Tsirkin <mst@redhat.com> Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
594 lines
16 KiB
C
594 lines
16 KiB
C
/*
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* Virtio balloon implementation, inspired by Dor Laor and Marcelo
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* Tosatti's implementations.
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*
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* Copyright 2008 Rusty Russell IBM Corporation
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
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*/
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#include <linux/virtio.h>
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#include <linux/virtio_balloon.h>
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#include <linux/swap.h>
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#include <linux/kthread.h>
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#include <linux/freezer.h>
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#include <linux/delay.h>
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#include <linux/slab.h>
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#include <linux/module.h>
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#include <linux/balloon_compaction.h>
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#include <linux/oom.h>
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/*
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* Balloon device works in 4K page units. So each page is pointed to by
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* multiple balloon pages. All memory counters in this driver are in balloon
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* page units.
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*/
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#define VIRTIO_BALLOON_PAGES_PER_PAGE (unsigned)(PAGE_SIZE >> VIRTIO_BALLOON_PFN_SHIFT)
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#define VIRTIO_BALLOON_ARRAY_PFNS_MAX 256
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#define OOM_VBALLOON_DEFAULT_PAGES 256
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#define VIRTBALLOON_OOM_NOTIFY_PRIORITY 80
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static int oom_pages = OOM_VBALLOON_DEFAULT_PAGES;
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module_param(oom_pages, int, S_IRUSR | S_IWUSR);
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MODULE_PARM_DESC(oom_pages, "pages to free on OOM");
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struct virtio_balloon
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{
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struct virtio_device *vdev;
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struct virtqueue *inflate_vq, *deflate_vq, *stats_vq;
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/* Where the ballooning thread waits for config to change. */
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wait_queue_head_t config_change;
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/* The thread servicing the balloon. */
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struct task_struct *thread;
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/* Waiting for host to ack the pages we released. */
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wait_queue_head_t acked;
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/* Number of balloon pages we've told the Host we're not using. */
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unsigned int num_pages;
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/*
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* The pages we've told the Host we're not using are enqueued
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* at vb_dev_info->pages list.
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* Each page on this list adds VIRTIO_BALLOON_PAGES_PER_PAGE
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* to num_pages above.
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*/
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struct balloon_dev_info vb_dev_info;
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/* Synchronize access/update to this struct virtio_balloon elements */
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struct mutex balloon_lock;
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/* The array of pfns we tell the Host about. */
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unsigned int num_pfns;
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u32 pfns[VIRTIO_BALLOON_ARRAY_PFNS_MAX];
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/* Memory statistics */
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int need_stats_update;
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struct virtio_balloon_stat stats[VIRTIO_BALLOON_S_NR];
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/* To register callback in oom notifier call chain */
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struct notifier_block nb;
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};
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static struct virtio_device_id id_table[] = {
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{ VIRTIO_ID_BALLOON, VIRTIO_DEV_ANY_ID },
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{ 0 },
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};
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static u32 page_to_balloon_pfn(struct page *page)
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{
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unsigned long pfn = page_to_pfn(page);
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BUILD_BUG_ON(PAGE_SHIFT < VIRTIO_BALLOON_PFN_SHIFT);
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/* Convert pfn from Linux page size to balloon page size. */
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return pfn * VIRTIO_BALLOON_PAGES_PER_PAGE;
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}
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static struct page *balloon_pfn_to_page(u32 pfn)
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{
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BUG_ON(pfn % VIRTIO_BALLOON_PAGES_PER_PAGE);
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return pfn_to_page(pfn / VIRTIO_BALLOON_PAGES_PER_PAGE);
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}
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static void balloon_ack(struct virtqueue *vq)
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{
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struct virtio_balloon *vb = vq->vdev->priv;
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wake_up(&vb->acked);
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}
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static void tell_host(struct virtio_balloon *vb, struct virtqueue *vq)
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{
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struct scatterlist sg;
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unsigned int len;
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sg_init_one(&sg, vb->pfns, sizeof(vb->pfns[0]) * vb->num_pfns);
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/* We should always be able to add one buffer to an empty queue. */
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virtqueue_add_outbuf(vq, &sg, 1, vb, GFP_KERNEL);
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virtqueue_kick(vq);
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/* When host has read buffer, this completes via balloon_ack */
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wait_event(vb->acked, virtqueue_get_buf(vq, &len));
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}
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static void set_page_pfns(u32 pfns[], struct page *page)
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{
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unsigned int i;
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/* Set balloon pfns pointing at this page.
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* Note that the first pfn points at start of the page. */
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for (i = 0; i < VIRTIO_BALLOON_PAGES_PER_PAGE; i++)
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pfns[i] = page_to_balloon_pfn(page) + i;
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}
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static void fill_balloon(struct virtio_balloon *vb, size_t num)
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{
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struct balloon_dev_info *vb_dev_info = &vb->vb_dev_info;
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/* We can only do one array worth at a time. */
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num = min(num, ARRAY_SIZE(vb->pfns));
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mutex_lock(&vb->balloon_lock);
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for (vb->num_pfns = 0; vb->num_pfns < num;
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vb->num_pfns += VIRTIO_BALLOON_PAGES_PER_PAGE) {
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struct page *page = balloon_page_enqueue(vb_dev_info);
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if (!page) {
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dev_info_ratelimited(&vb->vdev->dev,
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"Out of puff! Can't get %u pages\n",
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VIRTIO_BALLOON_PAGES_PER_PAGE);
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/* Sleep for at least 1/5 of a second before retry. */
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msleep(200);
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break;
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}
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set_page_pfns(vb->pfns + vb->num_pfns, page);
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vb->num_pages += VIRTIO_BALLOON_PAGES_PER_PAGE;
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adjust_managed_page_count(page, -1);
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}
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/* Did we get any? */
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if (vb->num_pfns != 0)
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tell_host(vb, vb->inflate_vq);
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mutex_unlock(&vb->balloon_lock);
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}
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static void release_pages_by_pfn(const u32 pfns[], unsigned int num)
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{
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unsigned int i;
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/* Find pfns pointing at start of each page, get pages and free them. */
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for (i = 0; i < num; i += VIRTIO_BALLOON_PAGES_PER_PAGE) {
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struct page *page = balloon_pfn_to_page(pfns[i]);
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adjust_managed_page_count(page, 1);
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put_page(page); /* balloon reference */
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}
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}
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static unsigned leak_balloon(struct virtio_balloon *vb, size_t num)
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{
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unsigned num_freed_pages;
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struct page *page;
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struct balloon_dev_info *vb_dev_info = &vb->vb_dev_info;
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/* We can only do one array worth at a time. */
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num = min(num, ARRAY_SIZE(vb->pfns));
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mutex_lock(&vb->balloon_lock);
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for (vb->num_pfns = 0; vb->num_pfns < num;
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vb->num_pfns += VIRTIO_BALLOON_PAGES_PER_PAGE) {
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page = balloon_page_dequeue(vb_dev_info);
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if (!page)
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break;
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set_page_pfns(vb->pfns + vb->num_pfns, page);
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vb->num_pages -= VIRTIO_BALLOON_PAGES_PER_PAGE;
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}
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num_freed_pages = vb->num_pfns;
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/*
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* Note that if
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* virtio_has_feature(vdev, VIRTIO_BALLOON_F_MUST_TELL_HOST);
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* is true, we *have* to do it in this order
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*/
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if (vb->num_pfns != 0)
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tell_host(vb, vb->deflate_vq);
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mutex_unlock(&vb->balloon_lock);
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release_pages_by_pfn(vb->pfns, vb->num_pfns);
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return num_freed_pages;
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}
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static inline void update_stat(struct virtio_balloon *vb, int idx,
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u16 tag, u64 val)
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{
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BUG_ON(idx >= VIRTIO_BALLOON_S_NR);
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vb->stats[idx].tag = tag;
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vb->stats[idx].val = val;
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}
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#define pages_to_bytes(x) ((u64)(x) << PAGE_SHIFT)
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static void update_balloon_stats(struct virtio_balloon *vb)
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{
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unsigned long events[NR_VM_EVENT_ITEMS];
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struct sysinfo i;
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int idx = 0;
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all_vm_events(events);
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si_meminfo(&i);
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update_stat(vb, idx++, VIRTIO_BALLOON_S_SWAP_IN,
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pages_to_bytes(events[PSWPIN]));
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update_stat(vb, idx++, VIRTIO_BALLOON_S_SWAP_OUT,
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pages_to_bytes(events[PSWPOUT]));
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update_stat(vb, idx++, VIRTIO_BALLOON_S_MAJFLT, events[PGMAJFAULT]);
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update_stat(vb, idx++, VIRTIO_BALLOON_S_MINFLT, events[PGFAULT]);
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update_stat(vb, idx++, VIRTIO_BALLOON_S_MEMFREE,
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pages_to_bytes(i.freeram));
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update_stat(vb, idx++, VIRTIO_BALLOON_S_MEMTOT,
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pages_to_bytes(i.totalram));
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}
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/*
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* While most virtqueues communicate guest-initiated requests to the hypervisor,
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* the stats queue operates in reverse. The driver initializes the virtqueue
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* with a single buffer. From that point forward, all conversations consist of
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* a hypervisor request (a call to this function) which directs us to refill
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* the virtqueue with a fresh stats buffer. Since stats collection can sleep,
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* we notify our kthread which does the actual work via stats_handle_request().
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*/
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static void stats_request(struct virtqueue *vq)
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{
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struct virtio_balloon *vb = vq->vdev->priv;
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vb->need_stats_update = 1;
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wake_up(&vb->config_change);
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}
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static void stats_handle_request(struct virtio_balloon *vb)
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{
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struct virtqueue *vq;
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struct scatterlist sg;
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unsigned int len;
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vb->need_stats_update = 0;
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update_balloon_stats(vb);
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vq = vb->stats_vq;
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if (!virtqueue_get_buf(vq, &len))
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return;
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sg_init_one(&sg, vb->stats, sizeof(vb->stats));
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virtqueue_add_outbuf(vq, &sg, 1, vb, GFP_KERNEL);
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virtqueue_kick(vq);
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}
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static void virtballoon_changed(struct virtio_device *vdev)
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{
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struct virtio_balloon *vb = vdev->priv;
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wake_up(&vb->config_change);
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}
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static inline s64 towards_target(struct virtio_balloon *vb)
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{
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__le32 v;
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s64 target;
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virtio_cread(vb->vdev, struct virtio_balloon_config, num_pages, &v);
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target = le32_to_cpu(v);
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return target - vb->num_pages;
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}
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static void update_balloon_size(struct virtio_balloon *vb)
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{
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__le32 actual = cpu_to_le32(vb->num_pages);
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virtio_cwrite(vb->vdev, struct virtio_balloon_config, actual,
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&actual);
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}
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/*
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* virtballoon_oom_notify - release pages when system is under severe
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* memory pressure (called from out_of_memory())
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* @self : notifier block struct
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* @dummy: not used
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* @parm : returned - number of freed pages
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*
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* The balancing of memory by use of the virtio balloon should not cause
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* the termination of processes while there are pages in the balloon.
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* If virtio balloon manages to release some memory, it will make the
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* system return and retry the allocation that forced the OOM killer
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* to run.
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*/
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static int virtballoon_oom_notify(struct notifier_block *self,
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unsigned long dummy, void *parm)
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{
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struct virtio_balloon *vb;
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unsigned long *freed;
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unsigned num_freed_pages;
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vb = container_of(self, struct virtio_balloon, nb);
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if (!virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM))
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return NOTIFY_OK;
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freed = parm;
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num_freed_pages = leak_balloon(vb, oom_pages);
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update_balloon_size(vb);
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*freed += num_freed_pages;
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return NOTIFY_OK;
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}
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static int balloon(void *_vballoon)
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{
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struct virtio_balloon *vb = _vballoon;
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set_freezable();
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while (!kthread_should_stop()) {
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s64 diff;
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try_to_freeze();
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wait_event_interruptible(vb->config_change,
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(diff = towards_target(vb)) != 0
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|| vb->need_stats_update
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|| kthread_should_stop()
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|| freezing(current));
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if (vb->need_stats_update)
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stats_handle_request(vb);
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if (diff > 0)
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fill_balloon(vb, diff);
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else if (diff < 0)
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leak_balloon(vb, -diff);
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update_balloon_size(vb);
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/*
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* For large balloon changes, we could spend a lot of time
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* and always have work to do. Be nice if preempt disabled.
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*/
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cond_resched();
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}
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return 0;
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}
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static int init_vqs(struct virtio_balloon *vb)
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{
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struct virtqueue *vqs[3];
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vq_callback_t *callbacks[] = { balloon_ack, balloon_ack, stats_request };
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const char *names[] = { "inflate", "deflate", "stats" };
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int err, nvqs;
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/*
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* We expect two virtqueues: inflate and deflate, and
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* optionally stat.
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*/
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nvqs = virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ) ? 3 : 2;
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err = vb->vdev->config->find_vqs(vb->vdev, nvqs, vqs, callbacks, names);
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if (err)
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return err;
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vb->inflate_vq = vqs[0];
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vb->deflate_vq = vqs[1];
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if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ)) {
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struct scatterlist sg;
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vb->stats_vq = vqs[2];
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/*
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* Prime this virtqueue with one buffer so the hypervisor can
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* use it to signal us later (it can't be broken yet!).
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*/
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sg_init_one(&sg, vb->stats, sizeof vb->stats);
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if (virtqueue_add_outbuf(vb->stats_vq, &sg, 1, vb, GFP_KERNEL)
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< 0)
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BUG();
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virtqueue_kick(vb->stats_vq);
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}
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return 0;
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}
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#ifdef CONFIG_BALLOON_COMPACTION
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/*
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* virtballoon_migratepage - perform the balloon page migration on behalf of
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* a compation thread. (called under page lock)
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* @vb_dev_info: the balloon device
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* @newpage: page that will replace the isolated page after migration finishes.
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* @page : the isolated (old) page that is about to be migrated to newpage.
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* @mode : compaction mode -- not used for balloon page migration.
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*
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* After a ballooned page gets isolated by compaction procedures, this is the
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* function that performs the page migration on behalf of a compaction thread
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* The page migration for virtio balloon is done in a simple swap fashion which
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* follows these two macro steps:
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* 1) insert newpage into vb->pages list and update the host about it;
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* 2) update the host about the old page removed from vb->pages list;
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*
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* This function preforms the balloon page migration task.
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* Called through balloon_mapping->a_ops->migratepage
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*/
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static int virtballoon_migratepage(struct balloon_dev_info *vb_dev_info,
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struct page *newpage, struct page *page, enum migrate_mode mode)
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{
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struct virtio_balloon *vb = container_of(vb_dev_info,
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struct virtio_balloon, vb_dev_info);
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unsigned long flags;
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/*
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* In order to avoid lock contention while migrating pages concurrently
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* to leak_balloon() or fill_balloon() we just give up the balloon_lock
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* this turn, as it is easier to retry the page migration later.
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* This also prevents fill_balloon() getting stuck into a mutex
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* recursion in the case it ends up triggering memory compaction
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* while it is attempting to inflate the ballon.
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*/
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if (!mutex_trylock(&vb->balloon_lock))
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return -EAGAIN;
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get_page(newpage); /* balloon reference */
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/* balloon's page migration 1st step -- inflate "newpage" */
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spin_lock_irqsave(&vb_dev_info->pages_lock, flags);
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balloon_page_insert(vb_dev_info, newpage);
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vb_dev_info->isolated_pages--;
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__count_vm_event(BALLOON_MIGRATE);
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spin_unlock_irqrestore(&vb_dev_info->pages_lock, flags);
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vb->num_pfns = VIRTIO_BALLOON_PAGES_PER_PAGE;
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set_page_pfns(vb->pfns, newpage);
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tell_host(vb, vb->inflate_vq);
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/* balloon's page migration 2nd step -- deflate "page" */
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balloon_page_delete(page);
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|
vb->num_pfns = VIRTIO_BALLOON_PAGES_PER_PAGE;
|
|
set_page_pfns(vb->pfns, page);
|
|
tell_host(vb, vb->deflate_vq);
|
|
|
|
mutex_unlock(&vb->balloon_lock);
|
|
|
|
put_page(page); /* balloon reference */
|
|
|
|
return MIGRATEPAGE_SUCCESS;
|
|
}
|
|
#endif /* CONFIG_BALLOON_COMPACTION */
|
|
|
|
static int virtballoon_probe(struct virtio_device *vdev)
|
|
{
|
|
struct virtio_balloon *vb;
|
|
int err;
|
|
|
|
vdev->priv = vb = kmalloc(sizeof(*vb), GFP_KERNEL);
|
|
if (!vb) {
|
|
err = -ENOMEM;
|
|
goto out;
|
|
}
|
|
|
|
vb->num_pages = 0;
|
|
mutex_init(&vb->balloon_lock);
|
|
init_waitqueue_head(&vb->config_change);
|
|
init_waitqueue_head(&vb->acked);
|
|
vb->vdev = vdev;
|
|
vb->need_stats_update = 0;
|
|
|
|
balloon_devinfo_init(&vb->vb_dev_info);
|
|
#ifdef CONFIG_BALLOON_COMPACTION
|
|
vb->vb_dev_info.migratepage = virtballoon_migratepage;
|
|
#endif
|
|
|
|
err = init_vqs(vb);
|
|
if (err)
|
|
goto out_free_vb;
|
|
|
|
vb->nb.notifier_call = virtballoon_oom_notify;
|
|
vb->nb.priority = VIRTBALLOON_OOM_NOTIFY_PRIORITY;
|
|
err = register_oom_notifier(&vb->nb);
|
|
if (err < 0)
|
|
goto out_oom_notify;
|
|
|
|
vb->thread = kthread_run(balloon, vb, "vballoon");
|
|
if (IS_ERR(vb->thread)) {
|
|
err = PTR_ERR(vb->thread);
|
|
goto out_del_vqs;
|
|
}
|
|
|
|
return 0;
|
|
|
|
out_del_vqs:
|
|
unregister_oom_notifier(&vb->nb);
|
|
out_oom_notify:
|
|
vdev->config->del_vqs(vdev);
|
|
out_free_vb:
|
|
kfree(vb);
|
|
out:
|
|
return err;
|
|
}
|
|
|
|
static void remove_common(struct virtio_balloon *vb)
|
|
{
|
|
/* There might be pages left in the balloon: free them. */
|
|
while (vb->num_pages)
|
|
leak_balloon(vb, vb->num_pages);
|
|
update_balloon_size(vb);
|
|
|
|
/* Now we reset the device so we can clean up the queues. */
|
|
vb->vdev->config->reset(vb->vdev);
|
|
|
|
vb->vdev->config->del_vqs(vb->vdev);
|
|
}
|
|
|
|
static void virtballoon_remove(struct virtio_device *vdev)
|
|
{
|
|
struct virtio_balloon *vb = vdev->priv;
|
|
|
|
unregister_oom_notifier(&vb->nb);
|
|
kthread_stop(vb->thread);
|
|
remove_common(vb);
|
|
kfree(vb);
|
|
}
|
|
|
|
#ifdef CONFIG_PM_SLEEP
|
|
static int virtballoon_freeze(struct virtio_device *vdev)
|
|
{
|
|
struct virtio_balloon *vb = vdev->priv;
|
|
|
|
/*
|
|
* The kthread is already frozen by the PM core before this
|
|
* function is called.
|
|
*/
|
|
|
|
remove_common(vb);
|
|
return 0;
|
|
}
|
|
|
|
static int virtballoon_restore(struct virtio_device *vdev)
|
|
{
|
|
struct virtio_balloon *vb = vdev->priv;
|
|
int ret;
|
|
|
|
ret = init_vqs(vdev->priv);
|
|
if (ret)
|
|
return ret;
|
|
|
|
virtio_device_ready(vdev);
|
|
|
|
fill_balloon(vb, towards_target(vb));
|
|
update_balloon_size(vb);
|
|
return 0;
|
|
}
|
|
#endif
|
|
|
|
static unsigned int features[] = {
|
|
VIRTIO_BALLOON_F_MUST_TELL_HOST,
|
|
VIRTIO_BALLOON_F_STATS_VQ,
|
|
VIRTIO_BALLOON_F_DEFLATE_ON_OOM,
|
|
};
|
|
|
|
static struct virtio_driver virtio_balloon_driver = {
|
|
.feature_table = features,
|
|
.feature_table_size = ARRAY_SIZE(features),
|
|
.driver.name = KBUILD_MODNAME,
|
|
.driver.owner = THIS_MODULE,
|
|
.id_table = id_table,
|
|
.probe = virtballoon_probe,
|
|
.remove = virtballoon_remove,
|
|
.config_changed = virtballoon_changed,
|
|
#ifdef CONFIG_PM_SLEEP
|
|
.freeze = virtballoon_freeze,
|
|
.restore = virtballoon_restore,
|
|
#endif
|
|
};
|
|
|
|
module_virtio_driver(virtio_balloon_driver);
|
|
MODULE_DEVICE_TABLE(virtio, id_table);
|
|
MODULE_DESCRIPTION("Virtio balloon driver");
|
|
MODULE_LICENSE("GPL");
|