nested vmx: Fix the booting of L2 PAE guest

When doing virtual VM entry and virtual VM exit, we need to
sychronize the PAE PDPTR related VMCS registers. With this fix,
we can boot 32bit PAE L2 guest (Win7 & RHEL6.4) on "Xen on Xen"
environment.

Signed-off-by: Dongxiao Xu <dongxiao.xu@intel.com>
Tested-by: Yongjie Ren <yongjie.ren@intel.com>
Acked-by: Keir Fraser <keir@xen.org>
Acked-by: "Dong, Eddie" <eddie.dong@intel.com>

xen/arch/x86/hvm/vmx/vvmx.c

@@ -864,6 +864,13 @@ static const u16 vmcs_gstate_field[] = {
     GUEST_SYSENTER_EIP,
 };
 
+static const u16 gpdptr_fields[] = {
+    GUEST_PDPTR0,
+    GUEST_PDPTR1,
+    GUEST_PDPTR2,
+    GUEST_PDPTR3,
+};
+
 /*
  * Context: shadow -> virtual VMCS
  */
@@ -1053,18 +1060,6 @@ static void load_shadow_guest_state(struct vcpu *v)
                      (__get_vvmcs(vvmcs, CR4_READ_SHADOW) & cr_gh_mask);
     __vmwrite(CR4_READ_SHADOW, cr_read_shadow);
 
-    if ( nvmx_ept_enabled(v) && hvm_pae_enabled(v) &&
-         (v->arch.hvm_vcpu.guest_efer & EFER_LMA) )
-    {
-        static const u16 gpdptr_fields[] = {
-            GUEST_PDPTR0,
-            GUEST_PDPTR1,
-            GUEST_PDPTR2,
-            GUEST_PDPTR3,
-        };
-        vvmcs_to_shadow_bulk(v, ARRAY_SIZE(gpdptr_fields), gpdptr_fields);
-    }
-
     /* TODO: CR3 target control */
 }
 
@@ -1159,6 +1154,10 @@ static void virtual_vmentry(struct cpu_user_regs *regs)
     if ( lm_l1 != lm_l2 )
         paging_update_paging_modes(v);
 
+    if ( nvmx_ept_enabled(v) && hvm_pae_enabled(v) &&
+         !(v->arch.hvm_vcpu.guest_efer & EFER_LMA) )
+        vvmcs_to_shadow_bulk(v, ARRAY_SIZE(gpdptr_fields), gpdptr_fields);
+
     regs->eip = __get_vvmcs(vvmcs, GUEST_RIP);
     regs->esp = __get_vvmcs(vvmcs, GUEST_RSP);
     regs->eflags = __get_vvmcs(vvmcs, GUEST_RFLAGS);
@@ -1294,6 +1293,10 @@ static void virtual_vmexit(struct cpu_user_regs *regs)
     sync_vvmcs_guest_state(v, regs);
     sync_exception_state(v);
 
+    if ( nvmx_ept_enabled(v) && hvm_pae_enabled(v) &&
+         !(v->arch.hvm_vcpu.guest_efer & EFER_LMA) )
+        shadow_to_vvmcs_bulk(v, ARRAY_SIZE(gpdptr_fields), gpdptr_fields);
+
     vmx_vmcs_switch(v->arch.hvm_vmx.vmcs, nvcpu->nv_n1vmcx);
 
     nestedhvm_vcpu_exit_guestmode(v);