File 5b34b8fe-VMX-defer-vmx_vmcs_exit-as-long-as-possible.patch of Package xen.10697

# Commit f30e3cf34042846e391e3f8361fc6a76d181a7ee
# Date 2018-06-28 11:31:26 +0100
# Author Andrew Cooper <andrew.cooper3@citrix.com>
# Committer Andrew Cooper <andrew.cooper3@citrix.com>
x86/vmx: Defer vmx_vmcs_exit() as long as possible in construct_vmcs()

paging_update_paging_modes() and vmx_vlapic_msr_changed() both operate on the
VMCS being constructed.  Avoid dropping and re-acquiring the reference
multiple times.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
Acked-by: Kevin Tian <kevin.tian@intel.com>

--- a/xen/arch/x86/hvm/vmx/vmcs.c
+++ b/xen/arch/x86/hvm/vmx/vmcs.c
@@ -875,6 +875,7 @@ static int construct_vmcs(struct vcpu *v
     unsigned long sysenter_eip;
     u32 vmexit_ctl = vmx_vmexit_control;
     u32 vmentry_ctl = vmx_vmentry_control;
+    int rc = 0;
 
     vmx_vmcs_enter(v);
 
@@ -961,8 +962,8 @@ static int construct_vmcs(struct vcpu *v
 
         if ( msr_bitmap == NULL )
         {
-            vmx_vmcs_exit(v);
-            return -ENOMEM;
+            rc = -ENOMEM;
+            goto out;
         }
 
         memset(msr_bitmap, ~0, PAGE_SIZE);
@@ -1150,8 +1151,6 @@ static int construct_vmcs(struct vcpu *v
         __vmwrite(GUEST_PAT, guest_pat);
     }
 
-    vmx_vmcs_exit(v);
-
     /* PVH: paging mode is updated by arch_set_info_guest(). */
     if ( is_hvm_vcpu(v) )
     {
@@ -1161,7 +1160,10 @@ static int construct_vmcs(struct vcpu *v
         vmx_vlapic_msr_changed(v);
     }
 
-    return 0;
+ out:
+    vmx_vmcs_exit(v);
+
+    return rc;
 }
 
 int vmx_read_guest_msr(u32 msr, u64 *val)