MN10300: Make the FPU operate in non-lazy mode under SMP

Make the FPU operate in non-lazy mode under SMP so that when the process that
is currently using the FPU migrates to a different CPU, we don't have to ping
its previous CPU to flush the FPU context.

Signed-off-by: Akira Takeuchi <takeuchi.akr@jp.panasonic.com>
Signed-off-by: Kiyoshi Owada <owada.kiyoshi@jp.panasonic.com>
Signed-off-by: David Howells <dhowells@redhat.com>

1 files changed, 56 insertions, 85 deletions

diff --git a/arch/mn10300/kernel/fpu.c b/arch/mn10300/kernel/fpu.c
index e705f25ad5ff..5f9c3fa19a85 100644
--- a/arch/mn10300/kernel/fpu.c
+++ b/arch/mn10300/kernel/fpu.c
@@ -12,56 +12,19 @@
 #include <asm/fpu.h>
 #include <asm/elf.h>
 #include <asm/exceptions.h>
+#include <asm/system.h>
 
+#ifdef CONFIG_LAZY_SAVE_FPU
 struct task_struct *fpu_state_owner;
+#endif
 
 /*
- * handle an exception due to the FPU being disabled
+ * error functions in FPU disabled exception
  */
-asmlinkage void fpu_disabled(struct pt_regs *regs, enum exception_code code)
+asmlinkage void fpu_disabled_in_kernel(struct pt_regs *regs)
 {
-        struct task_struct *tsk = current;
-
-        if (!user_mode(regs))
-                die_if_no_fixup("An FPU Disabled exception happened in"
-                                " kernel space\n",
-                                regs, code);
-
-#ifdef CONFIG_FPU
-        preempt_disable();
-
-        /* transfer the last process's FPU state to memory */
-        if (fpu_state_owner) {
-                fpu_save(&fpu_state_owner->thread.fpu_state);
-                fpu_state_owner->thread.uregs->epsw &= ~EPSW_FE;
-        }
-
-        /* the current process now owns the FPU state */
-        fpu_state_owner = tsk;
-        regs->epsw |= EPSW_FE;
-
-        /* load the FPU with the current process's FPU state or invent a new
-         * clean one if the process doesn't have one */
-        if (is_using_fpu(tsk)) {
-                fpu_restore(&tsk->thread.fpu_state);
-        } else {
-                fpu_init_state();
-                set_using_fpu(tsk);
-        }
-
-        preempt_enable();
-#else
-        {
-                siginfo_t info;
-
-                info.si_signo = SIGFPE;
-                info.si_errno = 0;
-                info.si_addr = (void *) tsk->thread.uregs->pc;
-                info.si_code = FPE_FLTINV;
-
-                force_sig_info(SIGFPE, &info, tsk);
-        }
-#endif  /* CONFIG_FPU */
+        die_if_no_fixup("An FPU Disabled exception happened in kernel space\n",
+                        regs, EXCEP_FPU_DISABLED);
 }
 
 /*
@@ -71,15 +34,16 @@ asmlinkage void fpu_disabled(struct pt_regs *regs, enum exception_code code)
  */
 asmlinkage void fpu_exception(struct pt_regs *regs, enum exception_code code)
 {
-        struct task_struct *tsk = fpu_state_owner;
+        struct task_struct *tsk = current;
         siginfo_t info;
+        u32 fpcr;
 
         if (!user_mode(regs))
                 die_if_no_fixup("An FPU Operation exception happened in"
                                 " kernel space\n",
                                 regs, code);
 
-        if (!tsk)
+        if (!is_using_fpu(tsk))
                 die_if_no_fixup("An FPU Operation exception happened,"
                                 " but the FPU is not in use",
                                 regs, code);
@@ -89,48 +53,45 @@ asmlinkage void fpu_exception(struct pt_regs *regs, enum exception_code code)
         info.si_addr = (void *) tsk->thread.uregs->pc;
         info.si_code = FPE_FLTINV;
 
-#ifdef CONFIG_FPU
-        {
-                u32 fpcr;
+        unlazy_fpu(tsk);
 
-                /* get FPCR (we need to enable the FPU whilst we do this) */
-                asm volatile("  or      %1,epsw         \n"
-#ifdef CONFIG_MN10300_PROC_MN103E010
-                             "  nop                     \n"
-                             "  nop                     \n"
-                             "  nop                     \n"
-#endif
-                             "  fmov    fpcr,%0         \n"
-#ifdef CONFIG_MN10300_PROC_MN103E010
-                             "  nop                     \n"
-                             "  nop                     \n"
-                             "  nop                     \n"
-#endif
-                             "  and     %2,epsw         \n"
-                             : "=&d"(fpcr)
-                             : "i"(EPSW_FE), "i"(~EPSW_FE)
-                             );
-
-                if (fpcr & FPCR_EC_Z)
-                        info.si_code = FPE_FLTDIV;
-                else if (fpcr & FPCR_EC_O)
-                        info.si_code = FPE_FLTOVF;
-                else if (fpcr & FPCR_EC_U)
-                        info.si_code = FPE_FLTUND;
-                else if (fpcr & FPCR_EC_I)
-                        info.si_code = FPE_FLTRES;
-        }
-#endif
+        fpcr = tsk->thread.fpu_state.fpcr;
+
+        if (fpcr & FPCR_EC_Z)
+                info.si_code = FPE_FLTDIV;
+        else if (fpcr & FPCR_EC_O)
+                info.si_code = FPE_FLTOVF;
+        else if (fpcr & FPCR_EC_U)
+                info.si_code = FPE_FLTUND;
+        else if (fpcr & FPCR_EC_I)
+                info.si_code = FPE_FLTRES;
 
         force_sig_info(SIGFPE, &info, tsk);
 }
 
 /*
+ * handle an FPU invalid_op exception
+ * - Derived from DO_EINFO() macro in arch/mn10300/kernel/traps.c
+ */
+asmlinkage void fpu_invalid_op(struct pt_regs *regs, enum exception_code code)
+{
+        siginfo_t info;
+
+        if (!user_mode(regs))
+                die_if_no_fixup("FPU invalid opcode", regs, code);
+
+        info.si_signo = SIGILL;
+        info.si_errno = 0;
+        info.si_code = ILL_COPROC;
+        info.si_addr = (void *) regs->pc;
+        force_sig_info(info.si_signo, &info, current);
+}
+
+/*
  * save the FPU state to a signal context
  */
 int fpu_setup_sigcontext(struct fpucontext *fpucontext)
 {
-#ifdef CONFIG_FPU
         struct task_struct *tsk = current;
 
         if (!is_using_fpu(tsk))
@@ -142,11 +103,19 @@ int fpu_setup_sigcontext(struct fpucontext *fpucontext)
          */
         preempt_disable();
 
+#ifndef CONFIG_LAZY_SAVE_FPU
+        if (tsk->thread.fpu_flags & THREAD_HAS_FPU) {
+                fpu_save(&tsk->thread.fpu_state);
+                tsk->thread.uregs->epsw &= ~EPSW_FE;
+                tsk->thread.fpu_flags &= ~THREAD_HAS_FPU;
+        }
+#else /* !CONFIG_LAZY_SAVE_FPU */
         if (fpu_state_owner == tsk) {
                 fpu_save(&tsk->thread.fpu_state);
                 fpu_state_owner->thread.uregs->epsw &= ~EPSW_FE;
                 fpu_state_owner = NULL;
         }
+#endif /* !CONFIG_LAZY_SAVE_FPU */
 
         preempt_enable();
 
@@ -161,9 +130,6 @@ int fpu_setup_sigcontext(struct fpucontext *fpucontext)
                 return -1;
 
         return 1;
-#else
-        return 0;
-#endif
 }
 
 /*
@@ -171,17 +137,23 @@ int fpu_setup_sigcontext(struct fpucontext *fpucontext)
  */
 void fpu_kill_state(struct task_struct *tsk)
 {
-#ifdef CONFIG_FPU
         /* disown anything left in the FPU */
         preempt_disable();
 
+#ifndef CONFIG_LAZY_SAVE_FPU
+        if (tsk->thread.fpu_flags & THREAD_HAS_FPU) {
+                tsk->thread.uregs->epsw &= ~EPSW_FE;
+                tsk->thread.fpu_flags &= ~THREAD_HAS_FPU;
+        }
+#else /* !CONFIG_LAZY_SAVE_FPU */
         if (fpu_state_owner == tsk) {
                 fpu_state_owner->thread.uregs->epsw &= ~EPSW_FE;
                 fpu_state_owner = NULL;
         }
+#endif /* !CONFIG_LAZY_SAVE_FPU */
 
         preempt_enable();
-#endif
+
         /* we no longer have a valid current FPU state */
         clear_using_fpu(tsk);
 }
@@ -195,8 +167,7 @@ int fpu_restore_sigcontext(struct fpucontext *fpucontext)
         int ret;
 
         /* load up the old FPU state */
-        ret = copy_from_user(&tsk->thread.fpu_state,
-                             fpucontext,
+        ret = copy_from_user(&tsk->thread.fpu_state, fpucontext,
                              min(sizeof(struct fpu_state_struct),
                                  sizeof(struct fpucontext)));
         if (!ret)