1 files changed, 17 insertions, 0 deletions

diff --git a/arch/x86/xen/p2m.c b/arch/x86/xen/p2m.c
index 8b7f18e200aa..b89983e9656f 100644
--- a/arch/x86/xen/p2m.c
+++ b/arch/x86/xen/p2m.c
@@ -263,6 +263,10 @@ void xen_setup_mfn_list_list(void)
         HYPERVISOR_shared_info->arch.pfn_to_mfn_frame_list_list =
                 virt_to_mfn(p2m_top_mfn);
         HYPERVISOR_shared_info->arch.max_pfn = xen_max_p2m_pfn;
+        HYPERVISOR_shared_info->arch.p2m_generation = 0;
+        HYPERVISOR_shared_info->arch.p2m_vaddr = (unsigned long)xen_p2m_addr;
+        HYPERVISOR_shared_info->arch.p2m_cr3 =
+                xen_pfn_to_cr3(virt_to_mfn(swapper_pg_dir));
 }
 
 /* Set up p2m_top to point to the domain-builder provided p2m pages */
@@ -478,8 +482,12 @@ static pte_t *alloc_p2m_pmd(unsigned long addr, pte_t *pte_pg)
 
                 ptechk = lookup_address(vaddr, &level);
                 if (ptechk == pte_pg) {
+                        HYPERVISOR_shared_info->arch.p2m_generation++;
+                        wmb(); /* Tools are synchronizing via p2m_generation. */
                         set_pmd(pmdp,
                                 __pmd(__pa(pte_newpg[i]) | _KERNPG_TABLE));
+                        wmb(); /* Tools are synchronizing via p2m_generation. */
+                        HYPERVISOR_shared_info->arch.p2m_generation++;
                         pte_newpg[i] = NULL;
                 }
 
@@ -577,8 +585,12 @@ static bool alloc_p2m(unsigned long pfn)
                 spin_lock_irqsave(&p2m_update_lock, flags);
 
                 if (pte_pfn(*ptep) == p2m_pfn) {
+                        HYPERVISOR_shared_info->arch.p2m_generation++;
+                        wmb(); /* Tools are synchronizing via p2m_generation. */
                         set_pte(ptep,
                                 pfn_pte(PFN_DOWN(__pa(p2m)), PAGE_KERNEL));
+                        wmb(); /* Tools are synchronizing via p2m_generation. */
+                        HYPERVISOR_shared_info->arch.p2m_generation++;
                         if (mid_mfn)
                                 mid_mfn[mididx] = virt_to_mfn(p2m);
                         p2m = NULL;
@@ -630,6 +642,11 @@ bool __set_phys_to_machine(unsigned long pfn, unsigned long mfn)
                 return true;
         }
 
+        /*
+         * The interface requires atomic updates on p2m elements.
+         * xen_safe_write_ulong() is using __put_user which does an atomic
+         * store via asm().
+         */
         if (likely(!xen_safe_write_ulong(xen_p2m_addr + pfn, mfn)))
                 return true;