On Thu, 2008-11-13 at 08:44 +1030, Rusty Russell wrote:
>
> Note that I still don't have a balloon patch: want to send me one?
linux: virtio-balloon: avoid implicit use of Linux page size in balloon interface
Make the balloon interface always use 4K pages, and convert Linux pfns if
necessary. This patch assumes that Linux's PAGE_SHIFT will never be less than
12.
Signed-off-by: Hollis Blanchard <hollisb@xxxxxxxxxx>
---
Only build-tested.
diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c
--- a/drivers/virtio/virtio_balloon.c
+++ b/drivers/virtio/virtio_balloon.c
@@ -56,6 +56,14 @@ static struct virtio_device_id id_table[
{ 0 },
};
+static u32 page_to_balloon_pfn(struct page *page)
+{
+ unsigned long pfn = page_to_pfn(page);
+
+ /* Convert pfn from Linux page size to balloon page size. */
+ return pfn >> (PAGE_SHIFT - VIRTIO_BALLOON_PFN_SHIFT);
+}
+
static void balloon_ack(struct virtqueue *vq)
{
struct virtio_balloon *vb;
@@ -99,7 +107,7 @@ static void fill_balloon(struct virtio_b
msleep(200);
break;
}
- vb->pfns[vb->num_pfns] = page_to_pfn(page);
+ vb->pfns[vb->num_pfns] = page_to_balloon_pfn(page);
totalram_pages--;
vb->num_pages++;
list_add(&page->lru, &vb->pages);
@@ -132,7 +140,7 @@ static void leak_balloon(struct virtio_b
for (vb->num_pfns = 0; vb->num_pfns < num; vb->num_pfns++) {
page = list_first_entry(&vb->pages, struct page, lru);
list_del(&page->lru);
- vb->pfns[vb->num_pfns] = page_to_pfn(page);
+ vb->pfns[vb->num_pfns] = page_to_balloon_pfn(page);
vb->num_pages--;
}
diff --git a/include/linux/virtio_balloon.h b/include/linux/virtio_balloon.h
--- a/include/linux/virtio_balloon.h
+++ b/include/linux/virtio_balloon.h
@@ -10,6 +10,9 @@
/* The feature bitmap for virtio balloon */
#define VIRTIO_BALLOON_F_MUST_TELL_HOST 0 /* Tell before reclaiming pages */
+/* Size of a PFN in the balloon interface. */
+#define VIRTIO_BALLOON_PFN_SHIFT 12
+
struct virtio_balloon_config
{
/* Number of pages host wants Guest to give up. */
--
Hollis Blanchard
IBM Linux Technology Center
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