[PATCH] x86/FPU: make vcpu_reset_fpu() build again with old gcc

[Jan Beulich]

Fields of anonymous structs/unions may not be part of an initializer for
rather old gcc.

Fixes: 49a068471d77 ("x86/fpu: Rework fpu_setup_fpu() uses to split it in two")
Signed-off-by: Jan Beulich <jbeul...@suse.com>

--- a/xen/arch/x86/i387.c
+++ b/xen/arch/x86/i387.c
@@ -306,13 +306,13 @@ void vcpu_reset_fpu(struct vcpu *v)
 {
     v->fpu_initialised = false;
     *v->arch.xsave_area = (struct xsave_struct) {
-        .fpu_sse = {
-            .mxcsr = MXCSR_DEFAULT,
-            .fcw = FCW_RESET,
-            .ftw = FXSAVE_FTW_RESET,
-        },
         .xsave_hdr.xstate_bv = X86_XCR0_X87,
     };
+
+    /* Old gcc doesn't permit these to be part of the initializer. */
+    v->arch.xsave_area->fpu_sse.mxcsr = MXCSR_DEFAULT;
+    v->arch.xsave_area->fpu_sse.fcw = FCW_RESET;
+    v->arch.xsave_area->fpu_sse.ftw = FXSAVE_FTW_RESET;
 }
 
 void vcpu_setup_fpu(struct vcpu *v, const void *data)