KVM: VMX: Setup canonical VMCS config prior to kvm_x86_vendor_init()

Setup the golden VMCS config during vmx_init(), before the call to
kvm_x86_vendor_init(), instead of waiting until the callback to do
hardware setup.  setup_vmcs_config() only touches VMX state, i.e. doesn't
poke anything in kvm.ko, and has no runtime dependencies beyond
hv_init_evmcs().

Setting the VMCS config early on will allow referencing VMCS and VMX
capabilities at any point during setup, e.g. to check for PERF_GLOBAL_CTRL
save/load support during mediated PMU initialization.

Tested-by: Xudong Hao <xudong.hao@intel.com>
Link: https://lore.kernel.org/r/20250806195706.1650976-15-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>

arch/x86/kvm/vmx/vmx.c

@@ -8359,8 +8359,6 @@ __init int vmx_hardware_setup(void)
 
 	vmx_setup_user_return_msrs();
 
-	if (setup_vmcs_config(&vmcs_config, &vmx_capability) < 0)
-		return -EIO;
 
 	if (boot_cpu_has(X86_FEATURE_NX))
 		kvm_enable_efer_bits(EFER_NX);
@@ -8584,11 +8582,18 @@ int __init vmx_init(void)
 		return -EOPNOTSUPP;
 
 	/*
-	 * Note, hv_init_evmcs() touches only VMX knobs, i.e. there's nothing
-	 * to unwind if a later step fails.
+	 * Note, VMCS and eVMCS configuration only touch VMX knobs/variables,
+	 * i.e. there's nothing to unwind if a later step fails.
 	 */
 	hv_init_evmcs();
 
+	/*
+	 * Parse the VMCS config and VMX capabilities before anything else, so
+	 * that the information is available to all setup flows.
+	 */
+	if (setup_vmcs_config(&vmcs_config, &vmx_capability) < 0)
+		return -EIO;
+
 	r = kvm_x86_vendor_init(&vt_init_ops);
 	if (r)
 		return r;