MIPS: Initialise MAARs on secondary CPUs

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@imgtec.com>
Signed-off-by: Paul Burton <paul.burton@imgtec.com>
Cc: linux-mips@linux-mips.org
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Steven J. Hill <Steven.Hill@imgtec.com>
Cc: Andrew Bresticker <abrestic@chromium.org>
Cc: Bjorn Helgaas <bhelgaas@google.com>
Cc: David Hildenbrand <dahi@linux.vnet.ibm.com>
Cc: linux-kernel@vger.kernel.org
Cc: Aaro Koskinen <aaro.koskinen@iki.fi>
Cc: James Hogan <james.hogan@imgtec.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Markos Chandras <markos.chandras@imgtec.com>
Cc: Hemmo Nieminen <hemmo.nieminen@iki.fi>
Cc: Alex Smith <alex.smith@imgtec.com>
Cc: Peter Zijlstra (Intel) <peterz@infradead.org>
Patchwork: https://patchwork.linux-mips.org/patch/11239/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

3 files changed, 36 insertions, 3 deletions

diff --git a/arch/mips/include/asm/maar.h b/arch/mips/include/asm/maar.h
index b02891f9caaf..21d9607c80d7 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 a31896c33716..bd4385a8e6e8 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 023c164b9eb6..8770e619185e 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
@@ -288,10 +289,14 @@ 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;
@@ -304,8 +309,14 @@ 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++) {
@@ -315,6 +326,9 @@ 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);
@@ -341,6 +355,14 @@ 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++;
+                }
         }
 }