[PATCH 4.19 49/49] x86/Xen: swap NX determination and GDT setup on BSP

Greg Kroah-Hartman
2021-05-24T16:09:27Z

From: Jan Beulich <jbeulich@suse.com>

commit ae897fda4f507e4b239f0bdfd578b3688ca96fb4 upstream.

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 36104cb9012a82e73 ("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: 36104cb9012a82e73 ("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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Link: https://lore.kernel.org/r/12a866b0-9e89-59f7-ebeb-a2a6cec0987a@suse.com
Signed-off-by: Juergen Gross <jgross@suse.com>
---
arch/x86/xen/enlighten_pv.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)

--- a/arch/x86/xen/enlighten_pv.c
+++ b/arch/x86/xen/enlighten_pv.c
@@ -1246,16 +1246,16 @@ asmlinkage __visible void __init xen_sta
/* 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);