KVM: nVMX: Allocate shadow vmcs

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 <abelg@il.ibm.com>
Reviewed-by: Orit Wasserman <owasserm@redhat.com>
Signed-off-by: Gleb Natapov <gleb@redhat.com>

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 1cdfb5d7580a9f6d6ffafe9f36d9676f4ba2d703..7b27af9a14d8b9926133e79dd260224f396ce153 100644 (file)
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -355,6 +355,7 @@ 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;
@@ -5527,6 +5528,7 @@ static int handle_vmon(struct kvm_vcpu *vcpu)
 {
        struct kvm_segment cs;
        struct vcpu_vmx *vmx = to_vmx(vcpu);
+       struct vmcs *shadow_vmcs;
 
        /* The Intel VMX Instruction Reference lists a bunch of bits that
         * are prerequisite to running VMXON, most notably cr4.VMXE must be
@@ -5555,6 +5557,16 @@ static int handle_vmon(struct kvm_vcpu *vcpu)
                skip_emulated_instruction(vcpu);
                return 1;
        }
+       if (enable_shadow_vmcs) {
+               shadow_vmcs = alloc_vmcs();
+               if (!shadow_vmcs)
+                       return -ENOMEM;
+               /* mark vmcs as shadow */
+               shadow_vmcs->revision_id |= (1u << 31);
+               /* init shadow vmcs */
+               vmcs_clear(shadow_vmcs);
+               vmx->nested.current_shadow_vmcs = shadow_vmcs;
+       }
 
        INIT_LIST_HEAD(&(vmx->nested.vmcs02_pool));
        vmx->nested.vmcs02_num = 0;