[PATCH 5/6] x86/vmx: Defer vmx_vmcs_exit() as long as possible in construct_vmcs()

[Andrew Cooper <andrew.cooper3@citrix.com>]

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>
---
CC: Jan Beulich <JBeulich@suse.com>
CC: Jun Nakajima <jun.nakajima@intel.com>
CC: Kevin Tian <kevin.tian@intel.com>
CC: Wei Liu <wei.liu2@citrix.com>
CC: Roger Pau Monné <roger.pau@citrix.com>
---
 xen/arch/x86/hvm/vmx/vmcs.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/xen/arch/x86/hvm/vmx/vmcs.c b/xen/arch/x86/hvm/vmx/vmcs.c
index be02be1..ce78f19 100644
--- a/xen/arch/x86/hvm/vmx/vmcs.c
+++ b/xen/arch/x86/hvm/vmx/vmcs.c
@@ -996,6 +996,7 @@ static int construct_vmcs(struct vcpu *v)
     struct domain *d = v->domain;
     u32 vmexit_ctl = vmx_vmexit_control;
     u32 vmentry_ctl = vmx_vmentry_control;
+    int rc;
 
     vmx_vmcs_enter(v);
 
@@ -1083,8 +1084,8 @@ 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);
@@ -1258,13 +1259,14 @@ static int construct_vmcs(struct vcpu *v)
     if ( cpu_has_vmx_tsc_scaling )
         __vmwrite(TSC_MULTIPLIER, d->arch.hvm_domain.tsc_scaling_ratio);
 
-    vmx_vmcs_exit(v);
-
     /* will update HOST & GUEST_CR3 as reqd */
     paging_update_paging_modes(v);
 
     vmx_vlapic_msr_changed(v);
 
+ out:
+    vmx_vmcs_exit(v);
+
     return 0;
 }
 
-- 
2.1.4


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