On Mon, 2011-03-07 at 18:06 +0000, Daniel De Graaf wrote:
> Grant mappings cause the PFN<->MFN mapping to be lost on the pages used
> for the mapping. Instead of leaking memory, use pages that have already
> been ballooned out and so have no valid mapping. This removes the need
> for the bad-page leak workaround as pages are repopulated by the balloon
> driver.
>
> Signed-off-by: Daniel De Graaf <dgdegra@xxxxxxxxxxxxx>
Acked-by: Ian Campbell <ian.campbell@xxxxxxxxxx>
> ---
> drivers/xen/gntdev.c | 41 ++++++++---------------------------------
> 1 files changed, 8 insertions(+), 33 deletions(-)
>
> diff --git a/drivers/xen/gntdev.c b/drivers/xen/gntdev.c
> index d43ff30..2faf797 100644
> --- a/drivers/xen/gntdev.c
> +++ b/drivers/xen/gntdev.c
> @@ -36,6 +36,7 @@
>
> #include <xen/xen.h>
> #include <xen/grant_table.h>
> +#include <xen/balloon.h>
> #include <xen/gntdev.h>
> #include <xen/events.h>
> #include <asm/xen/hypervisor.h>
> @@ -122,10 +123,12 @@ static struct grant_map *gntdev_alloc_map(struct
> gntdev_priv *priv, int count)
> NULL == add->pages)
> goto err;
>
> + i = get_ballooned_pages(count, add->pages, 1);
> + if (i != count) {
> + put_ballooned_pages(i, add->pages);
> + goto err;
> + }
> for (i = 0; i < count; i++) {
> - add->pages[i] = alloc_page(GFP_KERNEL | __GFP_HIGHMEM);
> - if (add->pages[i] == NULL)
> - goto err;
> add->map_ops[i].handle = -1;
> add->unmap_ops[i].handle = -1;
> }
> @@ -137,11 +140,6 @@ static struct grant_map *gntdev_alloc_map(struct
> gntdev_priv *priv, int count)
> return add;
>
> err:
> - if (add->pages)
> - for (i = 0; i < count; i++) {
> - if (add->pages[i])
> - __free_page(add->pages[i]);
> - }
> kfree(add->pages);
> kfree(add->grants);
> kfree(add->map_ops);
> @@ -184,8 +182,6 @@ static struct grant_map *gntdev_find_map_index(struct
> gntdev_priv *priv,
>
> static void gntdev_put_map(struct grant_map *map)
> {
> - int i;
> -
> if (!map)
> return;
>
> @@ -202,29 +198,7 @@ static void gntdev_put_map(struct grant_map *map)
> if (!use_ptemod)
> unmap_grant_pages(map, 0, map->count);
>
> - for (i = 0; i < map->count; i++) {
> - uint32_t check, *tmp;
> - if (!map->pages[i])
> - continue;
> - /* XXX When unmapping in an HVM domain, Xen will
> - * sometimes end up mapping the GFN to an invalid MFN.
> - * In this case, writes will be discarded and reads will
> - * return all 0xFF bytes. Leak these unusable GFNs
> - * until Xen supports fixing their p2m mapping.
> - *
> - * Confirmed present in Xen 4.1-RC3 with HVM source
> - */
> - tmp = kmap(map->pages[i]);
> - *tmp = 0xdeaddead;
> - mb();
> - check = *tmp;
> - kunmap(map->pages[i]);
> - if (check == 0xdeaddead)
> - __free_page(map->pages[i]);
> - else
> - pr_debug("Discard page %d=%ld\n", i,
> - page_to_pfn(map->pages[i]));
> - }
> + put_ballooned_pages(map->count, map->pages);
> }
> kfree(map->pages);
> kfree(map->grants);
> @@ -324,6 +298,7 @@ static int __unmap_grant_pages(struct grant_map *map, int
> offset, int pages)
> map->unmap_ops[offset+i].status);
> map->unmap_ops[offset+i].handle = -1;
> }
> +
> return err;
> }
>
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