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authorMichael S. Tsirkin <mst@redhat.com>2012-04-12 16:38:00 +0300
committerMichael S. Tsirkin <mst@redhat.com>2012-04-15 11:51:06 +0300
commit3ccc9372ed0fab33d20f10be3c1efd5776ff5913 (patch)
treec0e0422269e8d340906848e4993d268b8d4170ad /drivers/virtio
parent1a87228f5f1d316002c7c161316f5524592be766 (diff)
downloadvexpress-lsk-3ccc9372ed0fab33d20f10be3c1efd5776ff5913.tar.gz
virtio_balloon: fix handling of PAGE_SIZE != 4k
As reported by David Gibson, current code handles PAGE_SIZE != 4k completely wrong which can lead to guest memory corruption errors: - page_to_balloon_pfn is wrong: e.g. on system with 64K page size it gives the same pfn value for 16 different pages. - we also need to convert back to linux pfns when we free. - for each linux page we need to tell host about multiple balloon pages, but code only adds one pfn to the array. This patch fixes all that, tested with a 64k ppc64 kernel. Reported-by: David Gibson <david@gibson.dropbear.id.au> Tested-by: David Gibson <david@gibson.dropbear.id.au> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Diffstat (limited to 'drivers/virtio')
-rw-r--r--drivers/virtio/virtio_balloon.c51
1 files changed, 41 insertions, 10 deletions
diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c
index 9e95ca60200..c2d05a8279f 100644
--- a/drivers/virtio/virtio_balloon.c
+++ b/drivers/virtio/virtio_balloon.c
@@ -28,6 +28,13 @@
#include <linux/slab.h>
#include <linux/module.h>
+/*
+ * Balloon device works in 4K page units. So each page is pointed to by
+ * multiple balloon pages. All memory counters in this driver are in balloon
+ * page units.
+ */
+#define VIRTIO_BALLOON_PAGES_PER_PAGE (PAGE_SIZE >> VIRTIO_BALLOON_PFN_SHIFT)
+
struct virtio_balloon
{
struct virtio_device *vdev;
@@ -42,8 +49,13 @@ struct virtio_balloon
/* Waiting for host to ack the pages we released. */
struct completion acked;
- /* The pages we've told the Host we're not using. */
+ /* Number of balloon pages we've told the Host we're not using. */
unsigned int num_pages;
+ /*
+ * The pages we've told the Host we're not using.
+ * Each page on this list adds VIRTIO_BALLOON_PAGES_PER_PAGE
+ * to num_pages above.
+ */
struct list_head pages;
/* The array of pfns we tell the Host about. */
@@ -66,7 +78,13 @@ static u32 page_to_balloon_pfn(struct page *page)
BUILD_BUG_ON(PAGE_SHIFT < VIRTIO_BALLOON_PFN_SHIFT);
/* Convert pfn from Linux page size to balloon page size. */
- return pfn >> (PAGE_SHIFT - VIRTIO_BALLOON_PFN_SHIFT);
+ return pfn * VIRTIO_BALLOON_PAGES_PER_PAGE;
+}
+
+static struct page *balloon_pfn_to_page(u32 pfn)
+{
+ BUG_ON(pfn % VIRTIO_BALLOON_PAGES_PER_PAGE);
+ return pfn_to_page(pfn / VIRTIO_BALLOON_PAGES_PER_PAGE);
}
static void balloon_ack(struct virtqueue *vq)
@@ -96,12 +114,23 @@ static void tell_host(struct virtio_balloon *vb, struct virtqueue *vq)
wait_for_completion(&vb->acked);
}
+static void set_page_pfns(u32 pfns[], struct page *page)
+{
+ unsigned int i;
+
+ /* Set balloon pfns pointing at this page.
+ * Note that the first pfn points at start of the page. */
+ for (i = 0; i < VIRTIO_BALLOON_PAGES_PER_PAGE; i++)
+ pfns[i] = page_to_balloon_pfn(page) + i;
+}
+
static void fill_balloon(struct virtio_balloon *vb, size_t num)
{
/* We can only do one array worth at a time. */
num = min(num, ARRAY_SIZE(vb->pfns));
- for (vb->num_pfns = 0; vb->num_pfns < num; vb->num_pfns++) {
+ for (vb->num_pfns = 0; vb->num_pfns < num;
+ vb->num_pfns += VIRTIO_BALLOON_PAGES_PER_PAGE) {
struct page *page = alloc_page(GFP_HIGHUSER | __GFP_NORETRY |
__GFP_NOMEMALLOC | __GFP_NOWARN);
if (!page) {
@@ -113,9 +142,9 @@ static void fill_balloon(struct virtio_balloon *vb, size_t num)
msleep(200);
break;
}
- vb->pfns[vb->num_pfns] = page_to_balloon_pfn(page);
+ set_page_pfns(vb->pfns + vb->num_pfns, page);
+ vb->num_pages += VIRTIO_BALLOON_PAGES_PER_PAGE;
totalram_pages--;
- vb->num_pages++;
list_add(&page->lru, &vb->pages);
}
@@ -130,8 +159,9 @@ static void release_pages_by_pfn(const u32 pfns[], unsigned int num)
{
unsigned int i;
- for (i = 0; i < num; i++) {
- __free_page(pfn_to_page(pfns[i]));
+ /* Find pfns pointing at start of each page, get pages and free them. */
+ for (i = 0; i < num; i += VIRTIO_BALLOON_PAGES_PER_PAGE) {
+ __free_page(balloon_pfn_to_page(pfns[i]));
totalram_pages++;
}
}
@@ -143,11 +173,12 @@ static void leak_balloon(struct virtio_balloon *vb, size_t num)
/* We can only do one array worth at a time. */
num = min(num, ARRAY_SIZE(vb->pfns));
- for (vb->num_pfns = 0; vb->num_pfns < num; vb->num_pfns++) {
+ for (vb->num_pfns = 0; vb->num_pfns < num;
+ vb->num_pfns += VIRTIO_BALLOON_PAGES_PER_PAGE) {
page = list_first_entry(&vb->pages, struct page, lru);
list_del(&page->lru);
- vb->pfns[vb->num_pfns] = page_to_balloon_pfn(page);
- vb->num_pages--;
+ set_page_pfns(vb->pfns + vb->num_pfns, page);
+ vb->num_pages -= VIRTIO_BALLOON_PAGES_PER_PAGE;
}
/*