x86/setup: Read CR4 earlier in __start_xen()

This is necessary for read_cr4() to function correctly.  Move the EFER caching
at the same time.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
(cherry picked from commit 9851bc4939)

xen/arch/x86/setup.c

@@ -873,6 +873,9 @@ void __init noreturn __start_xen(unsigned long mbi_p)
 
     /* Full exception support from here on in. */
 
+    rdmsrl(MSR_EFER, this_cpu(efer));
+    asm volatile ( "mov %%cr4,%0" : "=r" (get_cpu_info()->cr4) );
+
     /* Enable NMIs.  Our loader (e.g. Tboot) may have left them disabled. */
     enable_nmis();
 
@@ -919,9 +922,6 @@ void __init noreturn __start_xen(unsigned long mbi_p)
 
     parse_video_info();
 
-    rdmsrl(MSR_EFER, this_cpu(efer));
-    asm volatile ( "mov %%cr4,%0" : "=r" (get_cpu_info()->cr4) );
-
     /* We initialise the serial devices very early so we can get debugging. */
     ns16550.io_base = 0x3f8;
     ns16550.irq     = 4;