nvmx: fix resource relinquish for nested VMX

The previous order of relinquish resource is:
relinquish_domain_resources() -> vcpu_destroy() ->
nvmx_vcpu_destroy().  However some L1 resources like nv_vvmcx and
io_bitmaps are free in nvmx_vcpu_destroy(), therefore the
relinquish_domain_resources() will not reduce the refcnt of the domain
to 0, therefore the latter vcpu release functions will not be called.

To fix this issue, we need to release the nv_vvmcx and io_bitmaps in
relinquish_domain_resources().

Besides, after destroy the nested vcpu, we need to switch the
vmx->vmcs back to the L1 and let the vcpu_destroy() logic to free the
L1 VMCS page.

Signed-off-by: Dongxiao Xu <dongxiao.xu@intel.com>
Committed-by: Keir Fraser <keir@xen.org>

xen/arch/x86/hvm/hvm.c

@@ -561,6 +561,9 @@ int hvm_domain_initialise(struct domain *d)
 
 void hvm_domain_relinquish_resources(struct domain *d)
 {
+    if ( hvm_funcs.nhvm_domain_relinquish_resources )
+        hvm_funcs.nhvm_domain_relinquish_resources(d);
+
     hvm_destroy_ioreq_page(d, &d->arch.hvm_domain.ioreq);
     hvm_destroy_ioreq_page(d, &d->arch.hvm_domain.buf_ioreq);
 

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

@@ -1547,7 +1547,8 @@ static struct hvm_function_table __read_mostly vmx_function_table = {
     .nhvm_vcpu_asid       = nvmx_vcpu_asid,
     .nhvm_vmcx_guest_intercepts_trap = nvmx_intercepts_exception,
     .nhvm_vcpu_vmexit_trap = nvmx_vmexit_trap,
-    .nhvm_intr_blocked    = nvmx_intr_blocked
+    .nhvm_intr_blocked    = nvmx_intr_blocked,
+    .nhvm_domain_relinquish_resources = nvmx_domain_relinquish_resources
 };
 
 struct hvm_function_table * __init start_vmx(void)

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

@@ -57,7 +57,15 @@ void nvmx_vcpu_destroy(struct vcpu *v)
 {
     struct nestedvcpu *nvcpu = &vcpu_nestedhvm(v);
 
-    nvmx_purge_vvmcs(v);
+    /* 
+     * When destroying the vcpu, it may be running on behalf of L2 guest.
+     * Therefore we need to switch the VMCS pointer back to the L1 VMCS,
+     * in order to avoid double free of L2 VMCS and the possible memory
+     * leak of L1 VMCS page.
+     */
+    if ( nvcpu->nv_n1vmcx )
+        v->arch.hvm_vmx.vmcs = nvcpu->nv_n1vmcx;
+
     if ( nvcpu->nv_n2vmcx ) {
         __vmpclear(virt_to_maddr(nvcpu->nv_n2vmcx));
         free_xenheap_page(nvcpu->nv_n2vmcx);
@@ -65,6 +73,14 @@ void nvmx_vcpu_destroy(struct vcpu *v)
     }
 }
  
+void nvmx_domain_relinquish_resources(struct domain *d)
+{
+    struct vcpu *v;
+
+    for_each_vcpu ( d, v )
+        nvmx_purge_vvmcs(v);
+}
+
 int nvmx_vcpu_reset(struct vcpu *v)
 {
     return 0;

xen/include/asm-x86/hvm/hvm.h

@@ -179,6 +179,7 @@ struct hvm_function_table {
     bool_t (*nhvm_vmcx_hap_enabled)(struct vcpu *v);
 
     enum hvm_intblk (*nhvm_intr_blocked)(struct vcpu *v);
+    void (*nhvm_domain_relinquish_resources)(struct domain *d);
 };
 
 extern struct hvm_function_table hvm_funcs;

xen/include/asm-x86/hvm/vmx/vvmx.h

@@ -96,6 +96,7 @@ uint32_t nvmx_vcpu_asid(struct vcpu *v);
 enum hvm_intblk nvmx_intr_blocked(struct vcpu *v);
 int nvmx_intercepts_exception(struct vcpu *v, 
                               unsigned int trap, int error_code);
+void nvmx_domain_relinquish_resources(struct domain *d);
 
 int nvmx_handle_vmxon(struct cpu_user_regs *regs);
 int nvmx_handle_vmxoff(struct cpu_user_regs *regs);