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Commit 1b4aa2fa authored by Hollis Blanchard's avatar Hollis Blanchard Committed by Rusty Russell
Browse files

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: default avatarHollis Blanchard <hollisb@us.ibm.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au> (modified)
parent 87c7d57c

drivers/virtio/virtio_balloon.c

+11 −2
Original line number Diff line number Diff line
@@ -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--;

	}

include/linux/virtio_balloon.h

+3 −0
Original line number Diff line number Diff line
@@ -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. */