[Xen-devel] [PATCH v2 4/6] x86/mtrr: Fix PAT init handling when MTRR MSR is disabled

[Toshi Kani <toshi.kani@xxxxxxx>]

get_mtrr_state() calls pat_init() on BSP even if MTRR is disabled
by its MSR.  This causes pat_init() to be called on BSP only since
APs do not call pat_init() when MTRR is disabled.  This inconsistency
between BSP and APs leads undefined behavior.

Move BSP's PAT init code from get_mtrr_state() to mtrr_bp_pat_init().
Change mtrr_bp_init() to call mtrr_bp_pat_init() if MTRR is enabled.
This keeps 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>
Cc: Borislav Petkov <bp@xxxxxxx>
Cc: Luis R. Rodriguez <mcgrof@xxxxxxxx>
Cc: Juergen Gross <jgross@xxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: H. Peter Anvin <hpa@xxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
---
 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(-)

diff --git a/arch/x86/kernel/cpu/mtrr/generic.c 
b/arch/x86/kernel/cpu/mtrr/generic.c
index fcbcb2f..a9d2e54 100644
--- 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);
 }
 
diff --git a/arch/x86/kernel/cpu/mtrr/main.c b/arch/x86/kernel/cpu/mtrr/main.c
index 2d7d8d7..6186ff4 100644
--- 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();
diff --git a/arch/x86/kernel/cpu/mtrr/mtrr.h b/arch/x86/kernel/cpu/mtrr/mtrr.h
index 951884d..6c7ced0 100644
--- 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_mtrr_context *ctxt);
 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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