Re: [PATCH] powerpc/kernel: improve FP and vector registers restoration

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 <leitao@debian.org>
Signed-off-by: Gustavo Romero <redacted>
---
 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(&current->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));