From 1b4aa2faeca1b9922033daf2475b6fc13b0ffea6 Mon Sep 17 00:00:00 2001
From: Hollis Blanchard <hollisb@us.ibm.com>
Date: Thu, 13 Nov 2008 15:48:33 -0600
Subject: [PATCH] virtio: 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@us.ibm.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au> (modified)
---
drivers/virtio/virtio_balloon.c | 13 +++++++++++--
include/linux/virtio_balloon.h | 3 +++
2 files changed, 14 insertions(+), 2 deletions(-)
diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c
index 62eab43152d..59268266b79 100644
--- a/drivers/virtio/virtio_balloon.c
+++ b/drivers/virtio/virtio_balloon.c
@@ -56,6 +56,15 @@ static struct virtio_device_id id_table[] = {
{ 0 },
};
+static u32 page_to_balloon_pfn(struct page *page)
+{
+ unsigned long pfn = page_to_pfn(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);
+}
+
static void balloon_ack(struct virtqueue *vq)
{
struct virtio_balloon *vb;
@@ -99,7 +108,7 @@ static void fill_balloon(struct virtio_balloon *vb, size_t num)
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 +141,7 @@ static void leak_balloon(struct virtio_balloon *vb, size_t num)
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
index c30c7bfbf39..8726ff77763 100644
--- 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. */
--
2.41.3