x86/mm: Fix paging_load

When restoring a p2m entry in the paging_load path, we were not updating the
m2p entry correctly.

Also take advantage of this to act on an old suggestion: once done with the
load, promote the p2m entry to the final guest accessible type. This simplifies
logic.

Tested to work with xenpaging.

Signed-off-by: Andres Lagar-Cavilla <andres@lagarcavilla.org>
Acked-by: Olaf Hering <olaf@aepfle.de>
Acked-by: Tim Deegan <tim@xen.org>
Committed-by: Tim Deegan <tim@xen.org>

1 files changed, 8 insertions, 10 deletions

diff --git a/xen/arch/x86/mm/p2m.c b/xen/arch/x86/mm/p2m.c
index 4a0ca8bb73..eb43683a03 100644
--- a/xen/arch/x86/mm/p2m.c
+++ b/xen/arch/x86/mm/p2m.c
@@ -975,7 +975,7 @@ void p2m_mem_paging_populate(struct domain *d, unsigned long gfn)
 int p2m_mem_paging_prep(struct domain *d, unsigned long gfn, uint64_t buffer)
 {
     struct page_info *page;
-    p2m_type_t p2mt, target_p2mt;
+    p2m_type_t p2mt;
     p2m_access_t a;
     mfn_t mfn;
     struct p2m_domain *p2m = p2m_get_hostp2m(d);
@@ -1033,15 +1033,13 @@ int p2m_mem_paging_prep(struct domain *d, unsigned long gfn, uint64_t buffer)
         }
     }
 
-    target_p2mt = (p2mt == p2m_ram_paging_in_start) ?
-        /* If we kicked the pager with a populate event, the pager will send
-         * a resume event back */
-        p2m_ram_paging_in :
-        /* If this was called asynchronously by the pager, then we can 
-         * transition directly to the final guest-accessible type */
-        (paging_mode_log_dirty(d) ? p2m_ram_logdirty : p2m_ram_rw);
-    /* Fix p2m mapping */
-    set_p2m_entry(p2m, gfn, mfn, PAGE_ORDER_4K, target_p2mt, a);
+    /* Make the page already guest-accessible. If the pager still has a
+     * pending resume operation, it will be idempotent p2m entry-wise,
+     * but will unpause the vcpu */
+    set_p2m_entry(p2m, gfn, mfn, PAGE_ORDER_4K, 
+                    paging_mode_log_dirty(d) ? p2m_ram_logdirty : 
+                    p2m_ram_rw, a);
+    set_gpfn_from_mfn(mfn_x(mfn), gfn);
 
     atomic_dec(&d->paged_pages);