Re: [PATCH v1 02/47] x86: mtrr: generalize run time disabling of MTRR

On Sat, Mar 28, 2015 at 12:56:30AM +0100, Luis R. Rodriguez wrote:

quoted

On Fri, Mar 27, 2015 at 02:40:17PM -0600, Toshi Kani wrote:

quoted

On Fri, 2015-03-20 at 16:17 -0700, Luis R. Rodriguez wrote:
 :

quoted

@@ -734,6 +742,7 @@ void __init mtrr_bp_init(void)
 	}
 
 	if (mtrr_if) {
+		mtrr_enabled = true;
 		set_num_var_ranges();
 		init_table();
 		if (use_intel()) {

                        get_mtrr_state();

After setting mtrr_enabled to true, get_mtrr_state() reads
MSR_MTRRdefType and sets 'mtrr_state.enabled', which also indicates if
MTRRs are enabled or not on the system.  So, potentially, we could have
a case that mtrr_enabled is set to true, but mtrr_state.enabled is set
to disabled when MTRRs are disabled by BIOS.

Thanks for the review, in this case then we should update mtrr_enabled to false.

quoted

ps.
I recently cleaned up this part of the MTRR code in the patch below,
which is currently available in the -mm & -next trees.
https://lkml.org/lkml/2015/3/24/1063

Great I will rebase and work with that and try to address this
consideration you have raised.

OK I'll mesh in this change as well in my next respin:

diff --git a/arch/x86/kernel/cpu/mtrr/generic.c b/arch/x86/kernel/cpu/mtrr/generic.c
index a83f27a..ecf7cb9 100644
--- a/arch/x86/kernel/cpu/mtrr/generic.c
+++ b/arch/x86/kernel/cpu/mtrr/generic.c

@@ -438,7 +438,7 @@ static void __init print_mtrr_state(void)
 }
 
 /* Grab all of the MTRR state for this CPU into *state */
-void __init get_mtrr_state(void)
+bool __init get_mtrr_state(void)
 {
 	struct mtrr_var_range *vrs;
 	unsigned long flags;

@@ -482,6 +482,8 @@ void __init get_mtrr_state(void)
 
 	post_set();
 	local_irq_restore(flags);
+
+	return !!mtrr_state.enabled;