[PATCH] nestedhvm: fix write access fault on ro mapping

[Christoph Egger <Christoph.Egger@amd.com>]

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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>
CC: Tim Deegan <tim@xen.org>


-- 
---to satisfy European Law for business letters:
Advanced Micro Devices GmbH
Einsteinring 24, 85689 Dornach b. Muenchen
Geschaeftsfuehrer: Alberto Bozzo, Andrew Bowd
Sitz: Dornach, Gemeinde Aschheim, Landkreis Muenchen
Registergericht Muenchen, HRB Nr. 43632

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diff -r ae0e96e156f3 xen/arch/x86/hvm/hvm.c
--- a/xen/arch/x86/hvm/hvm.c	Thu Jul 19 12:12:12 2012 +0200
+++ b/xen/arch/x86/hvm/hvm.c	Thu Jul 19 15:30:04 2012 +0200
@@ -1291,6 +1291,8 @@ int hvm_hap_nested_page_fault(unsigned l
             if ( !handle_mmio() )
                 hvm_inject_hw_exception(TRAP_gp_fault, 0);
             return 1;
+        case NESTEDHVM_PAGEFAULT_READONLY:
+            break;
         }
     }
 
diff -r ae0e96e156f3 xen/arch/x86/mm/hap/nested_hap.c
--- a/xen/arch/x86/mm/hap/nested_hap.c	Thu Jul 19 12:12:12 2012 +0200
+++ b/xen/arch/x86/mm/hap/nested_hap.c	Thu Jul 19 15:30:04 2012 +0200
@@ -141,23 +141,28 @@ nestedhap_fix_p2m(struct vcpu *v, struct
  */
 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_READONLY;
+    if ( access_w && p2m_is_readonly(*p2mt) )
         goto out;
 
     rc = NESTEDHVM_PAGEFAULT_ERROR;
-    if ( p2m_is_paging(p2mt) || p2m_is_shared(p2mt) || !p2m_is_ram(p2mt) )
+    if ( p2m_is_paging(*p2mt) || p2m_is_shared(*p2mt) || !p2m_is_ram(*p2mt) )
         goto out;
 
     rc = NESTEDHVM_PAGEFAULT_ERROR;
@@ -215,6 +220,7 @@ nestedhvm_hap_nested_page_fault(struct v
     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));
@@ -237,7 +243,9 @@ nestedhvm_hap_nested_page_fault(struct v
     }
 
     /* ==> 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) {
@@ -249,6 +257,8 @@ nestedhvm_hap_nested_page_fault(struct v
         break;
     case NESTEDHVM_PAGEFAULT_MMIO:
         return rv;
+    case NESTEDHVM_PAGEFAULT_READONLY:
+        return rv;
     default:
         BUG();
         break;
@@ -258,8 +268,8 @@ nestedhvm_hap_nested_page_fault(struct v
 
     /* 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 */);
+        p2mt_10,
+        p2m_access_rwx /* FIXME: Should use minimum permission. */);
 
     return NESTEDHVM_PAGEFAULT_DONE;
 }
diff -r ae0e96e156f3 xen/include/asm-x86/hvm/nestedhvm.h
--- a/xen/include/asm-x86/hvm/nestedhvm.h	Thu Jul 19 12:12:12 2012 +0200
+++ b/xen/include/asm-x86/hvm/nestedhvm.h	Thu Jul 19 15:30:04 2012 +0200
@@ -47,10 +47,11 @@ bool_t nestedhvm_vcpu_in_guestmode(struc
     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
+#define NESTEDHVM_PAGEFAULT_DONE       0
+#define NESTEDHVM_PAGEFAULT_INJECT     1
+#define NESTEDHVM_PAGEFAULT_ERROR      2
+#define NESTEDHVM_PAGEFAULT_MMIO       3
+#define NESTEDHVM_PAGEFAULT_READONLY   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);
 

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