Currently tsk->thread->load_vec and load_fp are not initialized during a task creation, which set garbage to these variables (non-zero value).
These variables will be checked later at restore_math() to validate if the FP and vectors are being utilized. Since these values might be non-zero, the restore_math() will continue to save the FP and vectors even if they were never utilized before the userspace application. load_fp and load_vec counters will then overflow and the FP and Altivec will be finally disabled, but before that condition is reached (counter overflow) several context switches restored FP and vector registers without need, causing a performance degradation. Signed-off-by: Breno Leitao <lei...@debian.org> Signed-off-by: Gustavo Romero <gusbrom...@gmail.com> --- arch/powerpc/kernel/process.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c index baae104b16c7..a9435397eab8 100644 --- a/arch/powerpc/kernel/process.c +++ b/arch/powerpc/kernel/process.c @@ -1666,6 +1666,7 @@ void start_thread(struct pt_regs *regs, unsigned long start, unsigned long sp) #ifdef CONFIG_VSX current->thread.used_vsr = 0; #endif + current->thread.load_fp = 0; memset(¤t->thread.fp_state, 0, sizeof(current->thread.fp_state)); current->thread.fp_save_area = NULL; #ifdef CONFIG_ALTIVEC @@ -1674,6 +1675,7 @@ void start_thread(struct pt_regs *regs, unsigned long start, unsigned long sp) current->thread.vr_save_area = NULL; current->thread.vrsave = 0; current->thread.used_vr = 0; + current->thread.load_vec = 0; #endif /* CONFIG_ALTIVEC */ #ifdef CONFIG_SPE memset(current->thread.evr, 0, sizeof(current->thread.evr)); -- 2.11.0