[Xen-devel] [PATCH 4.6 27/56] x86/mtrr: Fix PAT init handling when MTRR is disabled

[Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>]

4.6-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Toshi Kani <toshi.kani@xxxxxxx>

commit ad025a73f0e9344ac73ffe1b74c184033e08e7d5 upstream.

get_mtrr_state() calls pat_init() on BSP even if MTRR is disabled.
This results in calling pat_init() on BSP only since APs do not call
pat_init() when MTRR is disabled.  This inconsistency between BSP
and APs leads to undefined behavior.

Make BSP's calling condition to pat_init() consistent with AP's,
mtrr_ap_init() and mtrr_aps_init().

Signed-off-by: Toshi Kani <toshi.kani@xxxxxxx>
Reviewed-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Andy Lutomirski <luto@xxxxxxxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxx>
Cc: Brian Gerst <brgerst@xxxxxxxxx>
Cc: Denys Vlasenko <dvlasenk@xxxxxxxxxx>
Cc: H. Peter Anvin <hpa@xxxxxxxxx>
Cc: Juergen Gross <jgross@xxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Luis R. Rodriguez <mcgrof@xxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Toshi Kani <toshi.kani@xxxxxx>
Cc: elliott@xxxxxxx
Cc: konrad.wilk@xxxxxxxxxx
Cc: paul.gortmaker@xxxxxxxxxxxxx
Cc: xen-devel@xxxxxxxxxxxxxxxxxxxx
Link: 
http://lkml.kernel.org/r/1458769323-24491-6-git-send-email-toshi.kani@xxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 arch/x86/kernel/cpu/mtrr/generic.c |   24 ++++++++++++++----------
 arch/x86/kernel/cpu/mtrr/main.c    |    3 +++
 arch/x86/kernel/cpu/mtrr/mtrr.h    |    1 +
 3 files changed, 18 insertions(+), 10 deletions(-)

--- a/arch/x86/kernel/cpu/mtrr/generic.c
+++ b/arch/x86/kernel/cpu/mtrr/generic.c
@@ -444,11 +444,24 @@ static void __init print_mtrr_state(void
                pr_debug("TOM2: %016llx aka %lldM\n", mtrr_tom2, mtrr_tom2>>20);
 }
 
+/* PAT setup for BP. We need to go through sync steps here */
+void __init mtrr_bp_pat_init(void)
+{
+       unsigned long flags;
+
+       local_irq_save(flags);
+       prepare_set();
+
+       pat_init();
+
+       post_set();
+       local_irq_restore(flags);
+}
+
 /* Grab all of the MTRR state for this CPU into *state */
 bool __init get_mtrr_state(void)
 {
        struct mtrr_var_range *vrs;
-       unsigned long flags;
        unsigned lo, dummy;
        unsigned int i;
 
@@ -481,15 +494,6 @@ bool __init get_mtrr_state(void)
 
        mtrr_state_set = 1;
 
-       /* PAT setup for BP. We need to go through sync steps here */
-       local_irq_save(flags);
-       prepare_set();
-
-       pat_init();
-
-       post_set();
-       local_irq_restore(flags);
-
        return !!(mtrr_state.enabled & MTRR_STATE_MTRR_ENABLED);
 }
 
--- a/arch/x86/kernel/cpu/mtrr/main.c
+++ b/arch/x86/kernel/cpu/mtrr/main.c
@@ -752,6 +752,9 @@ void __init mtrr_bp_init(void)
                        /* BIOS may override */
                        __mtrr_enabled = get_mtrr_state();
 
+                       if (mtrr_enabled())
+                               mtrr_bp_pat_init();
+
                        if (mtrr_cleanup(phys_addr)) {
                                changed_by_mtrr_cleanup = 1;
                                mtrr_if->set_all();
--- a/arch/x86/kernel/cpu/mtrr/mtrr.h
+++ b/arch/x86/kernel/cpu/mtrr/mtrr.h
@@ -52,6 +52,7 @@ void set_mtrr_prepare_save(struct set_mt
 void fill_mtrr_var_range(unsigned int index,
                u32 base_lo, u32 base_hi, u32 mask_lo, u32 mask_hi);
 bool get_mtrr_state(void);
+void mtrr_bp_pat_init(void);
 
 extern void set_mtrr_ops(const struct mtrr_ops *ops);
 



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