[MIPS] FPU affinity for MT ASE.

Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

6 files changed, 72 insertions, 1 deletions

diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig
index f9be549645ea..87f0b79c6b15 100644
--- a/arch/mips/Kconfig
+++ b/arch/mips/Kconfig
@@ -1464,6 +1464,11 @@ config MIPS_VPE_LOADER
 
 endchoice
 
+config MIPS_MT_FPAFF
+        bool "Dynamic FPU affinity for FP-intensive threads"
+        depends on MIPS_MT
+        default y
+
 config MIPS_VPE_LOADER_TOM
         bool "Load VPE program into memory hidden from linux"
         depends on MIPS_VPE_LOADER
diff --git a/arch/mips/kernel/process.c b/arch/mips/kernel/process.c
index 8b393df460a2..199a06e873c6 100644
--- a/arch/mips/kernel/process.c
+++ b/arch/mips/kernel/process.c
@@ -185,6 +185,17 @@ int copy_thread(int nr, unsigned long clone_flags, unsigned long usp,
         childregs->cp0_status &= ~(ST0_CU2|ST0_CU1);
         clear_tsk_thread_flag(p, TIF_USEDFPU);
 
+#ifdef CONFIG_MIPS_MT_FPAFF
+        /*
+         * FPU affinity support is cleaner if we track the
+         * user-visible CPU affinity from the very beginning.
+         * The generic cpus_allowed mask will already have
+         * been copied from the parent before copy_thread
+         * is invoked.
+         */
+        p->thread.user_cpus_allowed = p->cpus_allowed;
+#endif /* CONFIG_MIPS_MT_FPAFF */
+
         if (clone_flags & CLONE_SETTLS)
                 ti->tp_value = regs->regs[7];
 
diff --git a/arch/mips/kernel/scall32-o32.S b/arch/mips/kernel/scall32-o32.S
index 4e36b87be1ed..a0ac0e5f61ad 100644
--- a/arch/mips/kernel/scall32-o32.S
+++ b/arch/mips/kernel/scall32-o32.S
@@ -569,8 +569,19 @@ einval:	li	v0, -EINVAL
         sys     sys_tkill               2
         sys     sys_sendfile64          5
         sys     sys_futex               6
+#ifdef CONFIG_MIPS_MT_FPAFF
+        /*
+         * For FPU affinity scheduling on MIPS MT processors, we need to
+         * intercept sys_sched_xxxaffinity() calls until we get a proper hook
+         * in kernel/sched.c.  Considered only temporary we only support these
+         * hooks for the 32-bit kernel - there is no MIPS64 MT processor atm.
+         */
+        sys     mipsmt_sys_sched_setaffinity    3
+        sys     mipsmt_sys_sched_getaffinity    3
+#else
         sys     sys_sched_setaffinity   3
         sys     sys_sched_getaffinity   3       /* 4240 */
+#endif /* CONFIG_MIPS_MT_FPAFF */
         sys     sys_io_setup            2
         sys     sys_io_destroy          1
         sys     sys_io_getevents        5
diff --git a/arch/mips/kernel/setup.c b/arch/mips/kernel/setup.c
index dcbfd27071f0..bcf1b10e518f 100644
--- a/arch/mips/kernel/setup.c
+++ b/arch/mips/kernel/setup.c
@@ -529,7 +529,10 @@ void __init setup_arch(char **cmdline_p)
 
 int __init fpu_disable(char *s)
 {
-        cpu_data[0].options &= ~MIPS_CPU_FPU;
+        int i;
+
+        for (i = 0; i < NR_CPUS; i++)
+                cpu_data[i].options &= ~MIPS_CPU_FPU;
 
         return 1;
 }
diff --git a/arch/mips/kernel/smp-mt.c b/arch/mips/kernel/smp-mt.c
index 19b8e4b31b79..57770902b9ae 100644
--- a/arch/mips/kernel/smp-mt.c
+++ b/arch/mips/kernel/smp-mt.c
@@ -150,6 +150,11 @@ void plat_smp_setup(void)
         unsigned long val;
         int i, num;
 
+#ifdef CONFIG_MIPS_MT_FPAFF
+        /* If we have an FPU, enroll ourselves in the FPU-full mask */
+        if (cpu_has_fpu)
+                cpu_set(0, mt_fpu_cpumask);
+#endif /* CONFIG_MIPS_MT_FPAFF */
         if (!cpu_has_mipsmt)
                 return;
 
@@ -312,6 +317,12 @@ void prom_smp_finish(void)
 {
         write_c0_compare(read_c0_count() + (8* mips_hpt_frequency/HZ));
 
+#ifdef CONFIG_MIPS_MT_FPAFF
+        /* If we have an FPU, enroll ourselves in the FPU-full mask */
+        if (cpu_has_fpu)
+                cpu_set(smp_processor_id(), mt_fpu_cpumask);
+#endif /* CONFIG_MIPS_MT_FPAFF */
+
         local_irq_enable();
 }
 
diff --git a/arch/mips/kernel/traps.c b/arch/mips/kernel/traps.c
index 6336fe8008ec..e9902d89dc0a 100644
--- a/arch/mips/kernel/traps.c
+++ b/arch/mips/kernel/traps.c
@@ -758,6 +758,36 @@ asmlinkage void do_cpu(struct pt_regs *regs)
                                                 &current->thread.fpu.soft);
                         if (sig)
                                 force_sig(sig, current);
+#ifdef CONFIG_MIPS_MT_FPAFF
+                        else {
+                        /*
+                         * MIPS MT processors may have fewer FPU contexts
+                         * than CPU threads. If we've emulated more than
+                         * some threshold number of instructions, force
+                         * migration to a "CPU" that has FP support.
+                         */
+                         if(mt_fpemul_threshold > 0
+                         && ((current->thread.emulated_fp++
+                            > mt_fpemul_threshold))) {
+                          /*
+                           * If there's no FPU present, or if the
+                           * application has already restricted
+                           * the allowed set to exclude any CPUs
+                           * with FPUs, we'll skip the procedure.
+                           */
+                          if (cpus_intersects(current->cpus_allowed,
+                                                mt_fpu_cpumask)) {
+                            cpumask_t tmask;
+
+                            cpus_and(tmask,
+                                        current->thread.user_cpus_allowed,
+                                        mt_fpu_cpumask);
+                            set_cpus_allowed(current, tmask);
+                            current->thread.mflags |= MF_FPUBOUND;
+                          }
+                         }
+                        }
+#endif /* CONFIG_MIPS_MT_FPAFF */
                 }
 
                 return;