x86/Xen: swap NX determination and GDT setup on BSP

xen_setup_gdt(), via xen_load_gdt_boot(), wants to adjust page tables.
For this to work when NX is not available, x86_configure_nx() needs to
be called first.

[jgross] Note that this is a revert of 0cef8edfeeb31621e ("x86/xen:
Delay get_cpu_cap until stack canary is established"), which is possible
now that we no longer support running as PV guest in 32-bit mode.

Cc: <stable.vger.kernel.org> # 5.9
Fixes: 0cef8edfeeb31621e ("x86/xen: Delay get_cpu_cap until stack canary is established")
Reported-by: Olaf Hering <olaf@aepfle.de>
Signed-off-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Juergen Gross <jgross@suse.com>
Link: https://lore.kernel.org/r/12a866b0-9e89-59f7-ebeb-a2a6cec0987a@suse.com
Signed-off-by: Juergen Gross <jgross@suse.com>

diff --git a/arch/x86/xen/enlighten_pv.c b/arch/x86/xen/enlighten_pv.c
index 17503fed20177ba8a258848a0ce3e4e7f8499fde..e87699aa2dc8263d29054bba0adf937f7841e978 100644 (file)
--- a/arch/x86/xen/enlighten_pv.c
+++ b/arch/x86/xen/enlighten_pv.c
@@ -1273,16 +1273,16 @@ asmlinkage __visible void __init xen_start_kernel(void)
        /* Get mfn list */
        xen_build_dynamic_phys_to_machine();
 
+       /* Work out if we support NX */
+       get_cpu_cap(&boot_cpu_data);
+       x86_configure_nx();
+
        /*
         * Set up kernel GDT and segment registers, mainly so that
         * -fstack-protector code can be executed.
         */
        xen_setup_gdt(0);
 
-       /* Work out if we support NX */
-       get_cpu_cap(&boot_cpu_data);
-       x86_configure_nx();
-
        /* Determine virtual and physical address sizes */
        get_cpu_address_sizes(&boot_cpu_data);