xen/p2m: Allocate p2m tracking pages on override

It is possible to add a p2m override on pages that are currently mapped
to INVALID_P2M_ENTRY; in particular, this will happen when using
ballooned pages in gntdev. This means that set_phys_to_machine must be
used instead of __set_phys_to_machine.

Signed-off-by: Daniel De Graaf <dgdegra@tycho.nsa.gov>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

1 files changed, 4 insertions, 2 deletions

diff --git a/arch/x86/xen/p2m.c b/arch/x86/xen/p2m.c
index 215a3ce61068..2a44edd606e5 100644
--- a/arch/x86/xen/p2m.c
+++ b/arch/x86/xen/p2m.c
@@ -671,7 +671,9 @@ int m2p_add_override(unsigned long mfn, struct page *page)
         page->private = mfn;
         page->index = pfn_to_mfn(pfn);
 
-        __set_phys_to_machine(pfn, FOREIGN_FRAME(mfn));
+        if (unlikely(!set_phys_to_machine(pfn, FOREIGN_FRAME(mfn))))
+                return -ENOMEM;
+
         if (!PageHighMem(page))
                 /* Just zap old mapping for now */
                 pte_clear(&init_mm, address, ptep);
@@ -709,7 +711,7 @@ int m2p_remove_override(struct page *page)
         spin_lock_irqsave(&m2p_override_lock, flags);
         list_del(&page->lru);
         spin_unlock_irqrestore(&m2p_override_lock, flags);
-        __set_phys_to_machine(pfn, page->index);
+        set_phys_to_machine(pfn, page->index);
 
         if (!PageHighMem(page))
                 set_pte_at(&init_mm, address, ptep,