[PATCH 08/11] xen p2m: transparently change the p2m mappings in the m2p override

[stefano.stabellini@eu.citrix.com]

From: Stefano Stabellini <stefano.stabellini@eu.citrix.com>

In m2p_add_override store the original mfn into page->index and then
change the p2m mapping, setting mfns as FOREIGN_FRAME.

In m2p_remove_override restore the original mapping.

Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
---
 arch/x86/xen/p2m.c |    4 ++++
 1 files changed, 4 insertions(+), 0 deletions(-)

diff --git a/arch/x86/xen/p2m.c b/arch/x86/xen/p2m.c
index 8db19d5..7dde8e4 100644
--- a/arch/x86/xen/p2m.c
+++ b/arch/x86/xen/p2m.c
@@ -407,8 +407,11 @@ static unsigned long mfn_hash(unsigned long mfn)
 void m2p_add_override(unsigned long mfn, struct page *page)
 {
 	unsigned long flags;
+	unsigned long pfn = page_to_pfn(page);
 	page->private = mfn;
+	page->index = pfn_to_mfn(pfn);
 
+	__set_phys_to_machine(pfn, FOREIGN_FRAME(mfn));
 	spin_lock_irqsave(&m2p_override_lock, flags);
 	list_add(&page->lru,  &m2p_overrides[mfn_hash(mfn)]);
 	spin_unlock_irqrestore(&m2p_override_lock, flags);
@@ -420,6 +423,7 @@ void 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(page_to_pfn(page), page->index);
 }
 
 struct page *m2p_find_override(unsigned long mfn)
-- 
1.5.6.5