nestedhvm: fix write access fault on ro mapping

Fix write access fault when host npt is mapped read-only.
In this case let the host handle the #NPF.
Apply host p2mt to hap-on-hap pagetable entry.
This fixes the l2 guest graphic display refresh problem.

Signed-off-by: Christoph Egger <Christoph.Egger@amd.com>
Acked-by: Tim Deegan <tim@xen.org>
Committed-by: Tim Deegan <tim@xen.org>

3 files changed, 36 insertions, 22 deletions

diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c
index 22c136b9d9..87c08a9b5d 100644
--- a/xen/arch/x86/hvm/hvm.c
+++ b/xen/arch/x86/hvm/hvm.c
@@ -1278,12 +1278,14 @@ int hvm_hap_nested_page_fault(unsigned long gpa,
          * into l1 guest if not fixable. The algorithm is
          * the same as for shadow paging.
          */
-        rv = nestedhvm_hap_nested_page_fault(v, gpa,
+        rv = nestedhvm_hap_nested_page_fault(v, &gpa,
                                              access_r, access_w, access_x);
         switch (rv) {
         case NESTEDHVM_PAGEFAULT_DONE:
             return 1;
-        case NESTEDHVM_PAGEFAULT_ERROR:
+        case NESTEDHVM_PAGEFAULT_L1_ERROR:
+            /* An error occured while translating gpa from
+             * l2 guest address to l1 guest address. */
             return 0;
         case NESTEDHVM_PAGEFAULT_INJECT:
             return -1;
@@ -1291,6 +1293,10 @@ int hvm_hap_nested_page_fault(unsigned long gpa,
             if ( !handle_mmio() )
                 hvm_inject_hw_exception(TRAP_gp_fault, 0);
             return 1;
+        case NESTEDHVM_PAGEFAULT_L0_ERROR:
+            /* gpa is now translated to l1 guest address, update gfn. */
+            gfn = gpa >> PAGE_SHIFT;
+            break;
         }
     }
 
diff --git a/xen/arch/x86/mm/hap/nested_hap.c b/xen/arch/x86/mm/hap/nested_hap.c
index 53963e098f..91f3ecaa52 100644
--- a/xen/arch/x86/mm/hap/nested_hap.c
+++ b/xen/arch/x86/mm/hap/nested_hap.c
@@ -141,26 +141,29 @@ nestedhap_fix_p2m(struct vcpu *v, struct p2m_domain *p2m,
  */
 static int
 nestedhap_walk_L0_p2m(struct p2m_domain *p2m, paddr_t L1_gpa, paddr_t *L0_gpa,
-                      unsigned int *page_order)
+                      p2m_type_t *p2mt,
+                      unsigned int *page_order,
+                      bool_t access_r, bool_t access_w, bool_t access_x)
 {
     mfn_t mfn;
-    p2m_type_t p2mt;
     p2m_access_t p2ma;
     int rc;
 
     /* walk L0 P2M table */
-    mfn = get_gfn_type_access(p2m, L1_gpa >> PAGE_SHIFT, &p2mt, &p2ma, 
+    mfn = get_gfn_type_access(p2m, L1_gpa >> PAGE_SHIFT, p2mt, &p2ma, 
                               0, page_order);
 
     rc = NESTEDHVM_PAGEFAULT_MMIO;
-    if ( p2m_is_mmio(p2mt) )
+    if ( p2m_is_mmio(*p2mt) )
         goto out;
 
-    rc = NESTEDHVM_PAGEFAULT_ERROR;
-    if ( p2m_is_paging(p2mt) || p2m_is_shared(p2mt) || !p2m_is_ram(p2mt) )
+    rc = NESTEDHVM_PAGEFAULT_L0_ERROR;
+    if ( access_w && p2m_is_readonly(*p2mt) )
+        goto out;
+
+    if ( p2m_is_paging(*p2mt) || p2m_is_shared(*p2mt) || !p2m_is_ram(*p2mt) )
         goto out;
 
-    rc = NESTEDHVM_PAGEFAULT_ERROR;
     if ( !mfn_valid(mfn) )
         goto out;
 
@@ -207,7 +210,7 @@ nestedhap_walk_L1_p2m(struct vcpu *v, paddr_t L2_gpa, paddr_t *L1_gpa,
  * Returns:
  */
 int
-nestedhvm_hap_nested_page_fault(struct vcpu *v, paddr_t L2_gpa,
+nestedhvm_hap_nested_page_fault(struct vcpu *v, paddr_t *L2_gpa,
     bool_t access_r, bool_t access_w, bool_t access_x)
 {
     int rv;
@@ -215,19 +218,20 @@ nestedhvm_hap_nested_page_fault(struct vcpu *v, paddr_t L2_gpa,
     struct domain *d = v->domain;
     struct p2m_domain *p2m, *nested_p2m;
     unsigned int page_order_21, page_order_10, page_order_20;
+    p2m_type_t p2mt_10;
 
     p2m = p2m_get_hostp2m(d); /* L0 p2m */
     nested_p2m = p2m_get_nestedp2m(v, nhvm_vcpu_hostcr3(v));
 
     /* walk the L1 P2M table */
-    rv = nestedhap_walk_L1_p2m(v, L2_gpa, &L1_gpa, &page_order_21,
+    rv = nestedhap_walk_L1_p2m(v, *L2_gpa, &L1_gpa, &page_order_21,
         access_r, access_w, access_x);
 
     /* let caller to handle these two cases */
     switch (rv) {
     case NESTEDHVM_PAGEFAULT_INJECT:
         return rv;
-    case NESTEDHVM_PAGEFAULT_ERROR:
+    case NESTEDHVM_PAGEFAULT_L1_ERROR:
         return rv;
     case NESTEDHVM_PAGEFAULT_DONE:
         break;
@@ -237,13 +241,16 @@ nestedhvm_hap_nested_page_fault(struct vcpu *v, paddr_t L2_gpa,
     }
 
     /* ==> we have to walk L0 P2M */
-    rv = nestedhap_walk_L0_p2m(p2m, L1_gpa, &L0_gpa, &page_order_10);
+    rv = nestedhap_walk_L0_p2m(p2m, L1_gpa, &L0_gpa,
+        &p2mt_10, &page_order_10,
+        access_r, access_w, access_x);
 
     /* let upper level caller to handle these two cases */
     switch (rv) {
     case NESTEDHVM_PAGEFAULT_INJECT:
         return rv;
-    case NESTEDHVM_PAGEFAULT_ERROR:
+    case NESTEDHVM_PAGEFAULT_L0_ERROR:
+        *L2_gpa = L1_gpa;
         return rv;
     case NESTEDHVM_PAGEFAULT_DONE:
         break;
@@ -257,9 +264,9 @@ nestedhvm_hap_nested_page_fault(struct vcpu *v, paddr_t L2_gpa,
     page_order_20 = min(page_order_21, page_order_10);
 
     /* fix p2m_get_pagetable(nested_p2m) */
-    nestedhap_fix_p2m(v, nested_p2m, L2_gpa, L0_gpa, page_order_20,
-        p2m_ram_rw,
-        p2m_access_rwx /* FIXME: Should use same permission as l1 guest */);
+    nestedhap_fix_p2m(v, nested_p2m, *L2_gpa, L0_gpa, page_order_20,
+        p2mt_10,
+        p2m_access_rwx /* FIXME: Should use minimum permission. */);
 
     return NESTEDHVM_PAGEFAULT_DONE;
 }
diff --git a/xen/include/asm-x86/hvm/nestedhvm.h b/xen/include/asm-x86/hvm/nestedhvm.h
index 22a3c54841..91fde0b21e 100644
--- a/xen/include/asm-x86/hvm/nestedhvm.h
+++ b/xen/include/asm-x86/hvm/nestedhvm.h
@@ -47,11 +47,12 @@ bool_t nestedhvm_vcpu_in_guestmode(struct vcpu *v);
     vcpu_nestedhvm(v).nv_guestmode = 0
 
 /* Nested paging */
-#define NESTEDHVM_PAGEFAULT_DONE   0
-#define NESTEDHVM_PAGEFAULT_INJECT 1
-#define NESTEDHVM_PAGEFAULT_ERROR  2
-#define NESTEDHVM_PAGEFAULT_MMIO   3
-int nestedhvm_hap_nested_page_fault(struct vcpu *v, paddr_t L2_gpa,
+#define NESTEDHVM_PAGEFAULT_DONE       0
+#define NESTEDHVM_PAGEFAULT_INJECT     1
+#define NESTEDHVM_PAGEFAULT_L1_ERROR   2
+#define NESTEDHVM_PAGEFAULT_L0_ERROR   3
+#define NESTEDHVM_PAGEFAULT_MMIO       4
+int nestedhvm_hap_nested_page_fault(struct vcpu *v, paddr_t *L2_gpa,
     bool_t access_r, bool_t access_w, bool_t access_x);
 
 /* IO permission map */