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xen/balloon: pre-allocate p2m entries for ballooned pages 

Pages returned by alloc_xenballooned_pages() will be used for grant
mapping which will call set_phys_to_machine() (in PV guests).

Ballooned pages are set as INVALID_P2M_ENTRY in the p2m and thus may
be using the (shared) missing tables and a subsequent
set_phys_to_machine() will need to allocate new tables.

Since the grant mapping may be done from a context that cannot sleep,
the p2m entries must already be allocated.

Signed-off-by: David Vrabel <david.vrabel@citrix.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
This commit is contained in:
David Vrabel 2015-07-22 14:50:37 +01:00
parent 8edfcf882e
commit 4a69c909de
1 changed files with 5 additions and 0 deletions
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5
drivers/xen/balloon.c
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@ -602,6 +602,11 @@ int alloc_xenballooned_pages(int nr_pages, struct page **pages)
page = balloon_retrieve(true);
if (page) {
pages[pgno++] = page;
#ifdef CONFIG_XEN_HAVE_PVMMU
ret = xen_alloc_p2m_entry(page_to_pfn(page));
if (ret < 0)
goto out_undo;
#endif
} else {
ret = add_ballooned_pages(nr_pages - pgno);
if (ret < 0)