1 files changed, 66 insertions, 10 deletions

diff --git a/arch/x86/xen/p2m.c b/arch/x86/xen/p2m.c
index 6e56b65edafb..a8ee9a45c359 100644
--- a/arch/x86/xen/p2m.c
+++ b/arch/x86/xen/p2m.c
@@ -161,7 +161,9 @@
 #include <asm/xen/page.h>
 #include <asm/xen/hypercall.h>
 #include <asm/xen/hypervisor.h>
+#include <xen/grant_table.h>
 
+#include "multicalls.h"
 #include "xen-ops.h"
 
 static void __init m2p_override_init(void);
@@ -676,7 +678,8 @@ static unsigned long mfn_hash(unsigned long mfn)
 }
 
 /* Add an MFN override for a particular page */
-int m2p_add_override(unsigned long mfn, struct page *page, bool clear_pte)
+int m2p_add_override(unsigned long mfn, struct page *page,
+                struct gnttab_map_grant_ref *kmap_op)
 {
         unsigned long flags;
         unsigned long pfn;
@@ -700,9 +703,20 @@ int m2p_add_override(unsigned long mfn, struct page *page, bool clear_pte)
         if (unlikely(!set_phys_to_machine(pfn, FOREIGN_FRAME(mfn))))
                 return -ENOMEM;
 
-        if (clear_pte && !PageHighMem(page))
-                /* Just zap old mapping for now */
-                pte_clear(&init_mm, address, ptep);
+        if (kmap_op != NULL) {
+                if (!PageHighMem(page)) {
+                        struct multicall_space mcs =
+                                xen_mc_entry(sizeof(*kmap_op));
+
+                        MULTI_grant_table_op(mcs.mc,
+                                        GNTTABOP_map_grant_ref, kmap_op, 1);
+
+                        xen_mc_issue(PARAVIRT_LAZY_MMU);
+                }
+                /* let's use dev_bus_addr to record the old mfn instead */
+                kmap_op->dev_bus_addr = page->index;
+                page->index = (unsigned long) kmap_op;
+        }
         spin_lock_irqsave(&m2p_override_lock, flags);
         list_add(&page->lru,  &m2p_overrides[mfn_hash(mfn)]);
         spin_unlock_irqrestore(&m2p_override_lock, flags);
@@ -736,14 +750,56 @@ int m2p_remove_override(struct page *page, bool clear_pte)
         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);
         WARN_ON(!PagePrivate(page));
         ClearPagePrivate(page);
-        if (clear_pte && !PageHighMem(page))
-                set_pte_at(&init_mm, address, ptep,
-                                pfn_pte(pfn, PAGE_KERNEL));
-                /* No tlb flush necessary because the caller already
-                 * left the pte unmapped. */
+
+        if (clear_pte) {
+                struct gnttab_map_grant_ref *map_op =
+                        (struct gnttab_map_grant_ref *) page->index;
+                set_phys_to_machine(pfn, map_op->dev_bus_addr);
+                if (!PageHighMem(page)) {
+                        struct multicall_space mcs;
+                        struct gnttab_unmap_grant_ref *unmap_op;
+
+                        /*
+                         * It might be that we queued all the m2p grant table
+                         * hypercalls in a multicall, then m2p_remove_override
+                         * get called before the multicall has actually been
+                         * issued. In this case handle is going to -1 because
+                         * it hasn't been modified yet.
+                         */
+                        if (map_op->handle == -1)
+                                xen_mc_flush();
+                        /*
+                         * Now if map_op->handle is negative it means that the
+                         * hypercall actually returned an error.
+                         */
+                        if (map_op->handle == GNTST_general_error) {
+                                printk(KERN_WARNING "m2p_remove_override: "
+                                                "pfn %lx mfn %lx, failed to modify kernel mappings",
+                                                pfn, mfn);
+                                return -1;
+                        }
+
+                        mcs = xen_mc_entry(
+                                        sizeof(struct gnttab_unmap_grant_ref));
+                        unmap_op = mcs.args;
+                        unmap_op->host_addr = map_op->host_addr;
+                        unmap_op->handle = map_op->handle;
+                        unmap_op->dev_bus_addr = 0;
+
+                        MULTI_grant_table_op(mcs.mc,
+                                        GNTTABOP_unmap_grant_ref, unmap_op, 1);
+
+                        xen_mc_issue(PARAVIRT_LAZY_MMU);
+
+                        set_pte_at(&init_mm, address, ptep,
+                                        pfn_pte(pfn, PAGE_KERNEL));
+                        __flush_tlb_single(address);
+                        map_op->host_addr = 0;
+                }
+        } else
+                set_phys_to_machine(pfn, page->index);
 
         return 0;
 }