arm64: fpsimd: add support to enable/disable fpsimd_settings.

Add support to enable/disable fpsimd_settings at runtime through
kernel command line.

fpsimd.fpsimd_settings=0 should disable it.

Change-Id: I14bf5f20e36ec4547aad45382cfffc91666a2ff4
Signed-off-by: Sanrio Alvares <salvares@codeaurora.org>

diff --git a/arch/arm64/include/asm/elf.h b/arch/arm64/include/asm/elf.h
index 6c0f356..9973366 100644 (file)
--- a/arch/arm64/include/asm/elf.h
+++ b/arch/arm64/include/asm/elf.h
@@ -180,8 +180,6 @@ typedef compat_elf_greg_t           compat_elf_gregset_t[COMPAT_ELF_NGREG];
 #define compat_start_thread            compat_start_thread
 #define COMPAT_SET_PERSONALITY(ex)                                     \
 do {                                                                   \
-       if (current->mm)                                                \
-               fpsimd_enable_trap();                                   \
        set_thread_flag(TIF_32BIT);                                     \
 } while (0)
 

diff --git a/arch/arm64/kernel/fpsimd.c b/arch/arm64/kernel/fpsimd.c
index 10133c0..74bc79e 100644 (file)
--- a/arch/arm64/kernel/fpsimd.c
+++ b/arch/arm64/kernel/fpsimd.c
@@ -20,6 +20,7 @@
 #include <linux/cpu.h>
 #include <linux/cpu_pm.h>
 #include <linux/kernel.h>
+#include <linux/module.h>
 #include <linux/init.h>
 #include <linux/sched.h>
 #include <linux/signal.h>
@@ -90,11 +91,17 @@
 static DEFINE_PER_CPU(struct fpsimd_state *, fpsimd_last_state);
 static DEFINE_PER_CPU(int, fpsimd_stg_enable);
 
+static int fpsimd_settings = 0x1; /* default = 0x1 */
+module_param(fpsimd_settings, int, 0644);
+
 /*
  * Trapped FP/ASIMD access.
  */
 void do_fpsimd_acc(unsigned int esr, struct pt_regs *regs)
 {
+       if (!fpsimd_settings)
+               return;
+
        fpsimd_disable_trap();
        fpsimd_settings_disable();
        this_cpu_write(fpsimd_stg_enable, 0);
@@ -102,6 +109,9 @@ void do_fpsimd_acc(unsigned int esr, struct pt_regs *regs)
 
 void do_fpsimd_acc_compat(unsigned int esr, struct pt_regs *regs)
 {
+       if (!fpsimd_settings)
+               return;
+
        fpsimd_disable_trap();
        fpsimd_settings_enable();
        this_cpu_write(fpsimd_stg_enable, 1);
@@ -144,7 +154,7 @@ void fpsimd_thread_switch(struct task_struct *next)
        if (current->mm && !test_thread_flag(TIF_FOREIGN_FPSTATE))
                fpsimd_save_state(&current->thread.fpsimd_state);
 
-       if (__this_cpu_read(fpsimd_stg_enable)) {
+       if (fpsimd_settings && __this_cpu_read(fpsimd_stg_enable)) {
                fpsimd_settings_disable();
                this_cpu_write(fpsimd_stg_enable, 0);
        }
@@ -167,6 +177,9 @@ void fpsimd_thread_switch(struct task_struct *next)
                        set_ti_thread_flag(task_thread_info(next),
                                           TIF_FOREIGN_FPSTATE);
 
+               if (!fpsimd_settings)
+                       return;
+
                if (test_ti_thread_flag(task_thread_info(next), TIF_32BIT))
                        fpsimd_enable_trap();
                else