Hi Breno, > Currently tsk->thread->load_vec and load_fp are not initialized > during a task creation, which set garbage to these variables > (non-zero value).
Nice catch! It seems like we should zero load_tm too though? Acked-by: Anton Blanchard <an...@samba.org> Anton > 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));