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virtio: avoid implicit use of Linux page size in balloon interface

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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)
This commit is contained in:
Hollis Blanchard 2008-11-13 15:48:33 -06:00 committed by Rusty Russell
parent 87c7d57c17
commit 1b4aa2faec
2 changed files with 14 additions and 2 deletions
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13
drivers/virtio/virtio_balloon.c
View File

@ -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--;
}

3
include/linux/virtio_balloon.h
View File

@ -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. */