Allocate a shadow vmcs used by the processor to shadow part of the fields
stored in the software defined VMCS12 (let L1 access fields without causing
exits). Note we keep a shadow vmcs only for the current vmcs12.  Once a vmcs12
becomes non-current, its shadow vmcs is released.


Signed-off-by: Abel Gordon <ab...@il.ibm.com>
---
 arch/x86/kvm/vmx.c |   15 +++++++++++++++
 1 file changed, 15 insertions(+)

--- .before/arch/x86/kvm/vmx.c  2013-03-10 18:00:55.000000000 +0200
+++ .after/arch/x86/kvm/vmx.c   2013-03-10 18:00:55.000000000 +0200
@@ -353,6 +353,7 @@ struct nested_vmx {
        /* The host-usable pointer to the above */
        struct page *current_vmcs12_page;
        struct vmcs12 *current_vmcs12;
+       struct vmcs *current_shadow_vmcs;
 
        /* vmcs02_list cache of VMCSs recently used to run L2 guests */
        struct list_head vmcs02_pool;
@@ -5889,6 +5890,7 @@ static int handle_vmptrld(struct kvm_vcp
        gva_t gva;
        gpa_t vmptr;
        struct x86_exception e;
+       struct vmcs *shadow_vmcs;
        ++vcpu->stat.nvmx_vmptrlds;
 
        if (!nested_vmx_check_permission(vcpu))
@@ -5936,6 +5938,19 @@ static int handle_vmptrld(struct kvm_vcp
                vmx->nested.current_vmptr = vmptr;
                vmx->nested.current_vmcs12 = new_vmcs12;
                vmx->nested.current_vmcs12_page = page;
+               if (enable_shadow_vmcs) {
+                       shadow_vmcs = alloc_vmcs();
+                       if (!shadow_vmcs) {
+                               nested_vmx_failInvalid(vcpu);
+                               skip_emulated_instruction(vcpu);
+                               return 1;
+                       }
+                       /* mark vmcs as shadow */
+                       shadow_vmcs->revision_id |= (1u << 31);
+                       /* init shadow vmcs */
+                       vmcs_clear(shadow_vmcs);
+                       vmx->nested.current_shadow_vmcs = shadow_vmcs;
+               }
        }
 
        nested_vmx_succeed(vcpu);

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