From 99c13b8c8896d7bcb92753bf0c63a8de4326e78d Mon Sep 17 00:00:00 2001 From: Mikulas Patocka Date: Tue, 4 Jul 2017 19:04:23 -0400 Subject: x86/mm/pat: Don't report PAT on CPUs that don't support it The pat_enabled() logic is broken on CPUs which do not support PAT and where the initialization code fails to call pat_init(). Due to that the enabled flag stays true and pat_enabled() returns true wrongfully. As a consequence the mappings, e.g. for Xorg, are set up with the wrong caching mode and the required MTRR setups are omitted. To cure this the following changes are required: 1) Make pat_enabled() return true only if PAT initialization was invoked and successful. 2) Invoke init_cache_modes() unconditionally in setup_arch() and remove the extra callsites in pat_disable() and the pat disabled code path in pat_init(). Also rename __pat_enabled to pat_disabled to reflect the real purpose of this variable. Fixes: 9cd25aac1f44 ("x86/mm/pat: Emulate PAT when it is disabled") Signed-off-by: Mikulas Patocka Signed-off-by: Thomas Gleixner Cc: Bernhard Held Cc: Denys Vlasenko Cc: Peter Zijlstra Cc: Brian Gerst Cc: "Luis R. Rodriguez" Cc: Borislav Petkov Cc: Andy Lutomirski Cc: Josh Poimboeuf Cc: Andrew Morton Cc: Linus Torvalds Cc: stable@vger.kernel.org Link: http://lkml.kernel.org/r/alpine.LRH.2.02.1707041749300.3456@file01.intranet.prod.int.rdu2.redhat.com --- arch/x86/kernel/setup.c | 7 +++++++ 1 file changed, 7 insertions(+) (limited to 'arch/x86/kernel/setup.c') diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c index 65622f07e633..3486d0498800 100644 --- a/arch/x86/kernel/setup.c +++ b/arch/x86/kernel/setup.c @@ -1075,6 +1075,13 @@ void __init setup_arch(char **cmdline_p) max_possible_pfn = max_pfn; + /* + * This call is required when the CPU does not support PAT. If + * mtrr_bp_init() invoked it already via pat_init() the call has no + * effect. + */ + init_cache_modes(); + /* * Define random base addresses for memory sections after max_pfn is * defined and before each memory section base is used. -- cgit v1.2.3