--- a/xen/arch/x86/xstate.c
+++ b/xen/arch/x86/xstate.c
@@ -72,9 +72,24 @@ void xsave(struct vcpu *v, uint64_t mask
     if ( word_size <= 0 || !is_pv_32bit_vcpu(v) )
     {
         if ( cpu_has_xsaveopt )
+        {
+            /*
+             * xsaveopt may not write the FPU portion even when the respective
+             * mask bit is set. For the check further down to work we hence
+             * need to put the save image back into the state that it was in
+             * right after the previous xsaveopt.
+             */
+            if ( word_size > 0 &&
+                 (ptr->fpu_sse.x[FPU_WORD_SIZE_OFFSET] == 4 ||
+                  ptr->fpu_sse.x[FPU_WORD_SIZE_OFFSET] == 2) )
+            {
+                ptr->fpu_sse.fip.sel = 0;
+                ptr->fpu_sse.fdp.sel = 0;
+            }
             asm volatile ( ".byte 0x48,0x0f,0xae,0x37"
                            : "=m" (*ptr)
                            : "a" (lmask), "d" (hmask), "D" (ptr) );
+        }
         else
             asm volatile ( ".byte 0x48,0x0f,0xae,0x27"
                            : "=m" (*ptr)