[PATCH 2/2] MIPS: initialise MAARs on secondary CPUs

[Paul Burton <paul.burton@xxxxxxxxxx>]

MAARs should be initialised on each CPU (or rather, core) in the system
in order to achieve consistent behaviour & performance. Previously they
have only been initialised on the boot CPU which leads to performance
problems if tasks are later scheduled on a secondary CPU, particularly
if those tasks make use of unaligned vector accesses where some CPUs
don't handle any cases in hardware for non-speculative memory regions.
Fix this by recording the MAAR configuration from the boot CPU and
applying it to secondary CPUs as part of their bringup.

Reported-by: Doug Gilmore <doug.gilmore@xxxxxxxxxx>
Signed-off-by: Paul Burton <paul.burton@xxxxxxxxxx>
---

 arch/mips/include/asm/maar.h |  9 +++++++++
 arch/mips/kernel/smp.c       |  2 ++
 arch/mips/mm/init.c          | 28 +++++++++++++++++++++++++---
 3 files changed, 36 insertions(+), 3 deletions(-)

diff --git a/arch/mips/include/asm/maar.h b/arch/mips/include/asm/maar.h
index b02891f..21d9607 100644
--- a/arch/mips/include/asm/maar.h
+++ b/arch/mips/include/asm/maar.h
@@ -66,6 +66,15 @@ static inline void write_maar_pair(unsigned idx, phys_addr_t lower,
 }
 
 /**
+ * maar_init() - initialise MAARs
+ *
+ * Performs initialisation of MAARs for the current CPU, making use of the
+ * platforms implementation of platform_maar_init where necessary and
+ * duplicating the setup it provides on secondary CPUs.
+ */
+extern void maar_init(void);
+
+/**
  * struct maar_config - MAAR configuration data
  * @lower:	The lowest address that the MAAR pair will affect. Must be
  *		aligned to a 2^16 byte boundary.
diff --git a/arch/mips/kernel/smp.c b/arch/mips/kernel/smp.c
index a31896c..bd4385a 100644
--- a/arch/mips/kernel/smp.c
+++ b/arch/mips/kernel/smp.c
@@ -42,6 +42,7 @@
 #include <asm/mmu_context.h>
 #include <asm/time.h>
 #include <asm/setup.h>
+#include <asm/maar.h>
 
 cpumask_t cpu_callin_map;		/* Bitmask of started secondaries */
 
@@ -157,6 +158,7 @@ asmlinkage void start_secondary(void)
 	mips_clockevent_init();
 	mp_ops->init_secondary();
 	cpu_report();
+	maar_init();
 
 	/*
 	 * XXX parity protection should be folded in here when it's converted
diff --git a/arch/mips/mm/init.c b/arch/mips/mm/init.c
index cbef5c2..5f3c5b1 100644
--- a/arch/mips/mm/init.c
+++ b/arch/mips/mm/init.c
@@ -44,6 +44,7 @@
 #include <asm/pgalloc.h>
 #include <asm/tlb.h>
 #include <asm/fixmap.h>
+#include <asm/maar.h>
 
 /*
  * We have up to 8 empty zeroed pages so we can map one of the right colour
@@ -370,10 +371,14 @@ unsigned __weak platform_maar_init(unsigned num_pairs)
 	return num_configured;
 }
 
-static void maar_init(void)
+void maar_init(void)
 {
 	unsigned num_maars, used, i;
 	phys_addr_t lower, upper, attr;
+	static struct {
+		struct maar_config cfgs[3];
+		unsigned used;
+	} recorded = { { { 0 } }, 0 };
 
 	if (!cpu_has_maar)
 		return;
@@ -386,8 +391,14 @@ static void maar_init(void)
 	/* MAARs should be in pairs */
 	WARN_ON(num_maars % 2);
 
-	/* Configure the required MAARs */
-	used = platform_maar_init(num_maars / 2);
+	/* Set MAARs using values we recorded already */
+	if (recorded.used) {
+		used = maar_config(recorded.cfgs, recorded.used, num_maars / 2);
+		BUG_ON(used != recorded.used);
+	} else {
+		/* Configure the required MAARs */
+		used = platform_maar_init(num_maars / 2);
+	}
 
 	/* Disable any further MAARs */
 	for (i = (used * 2); i < num_maars; i++) {
@@ -397,6 +408,9 @@ static void maar_init(void)
 		back_to_back_c0_hazard();
 	}
 
+	if (recorded.used)
+		return;
+
 	pr_info("MAAR configuration:\n");
 	for (i = 0; i < num_maars; i += 2) {
 		write_c0_maari(i);
@@ -423,6 +437,14 @@ static void maar_init(void)
 			pr_cont(" speculate");
 
 		pr_cont("\n");
+
+		/* Record the setup for use on secondary CPUs */
+		if (used <= ARRAY_SIZE(recorded.cfgs)) {
+			recorded.cfgs[recorded.used].lower = lower;
+			recorded.cfgs[recorded.used].upper = upper;
+			recorded.cfgs[recorded.used].attrs = attr;
+			recorded.used++;
+		}
 	}
 }
 
-- 
2.5.3