[PATCH 17/22] x86/fpu: Prepare copy_fpstate_to_sigframe() for TIF_NEED_FPU_LOAD

Sebastian Andrzej Siewior
2019-01-09T11:47:39Z

From: Rik van Riel <riel@surriel.com>

The FPU registers need only to be saved if TIF_NEED_FPU_LOAD is not set.
Otherwise this has been already done and can be skipped.

Signed-off-by: Rik van Riel <riel@surriel.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
arch/x86/kernel/fpu/signal.c | 11 ++++++++++-
1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kernel/fpu/signal.c b/arch/x86/kernel/fpu/signal.c
index bf4e6caad305e..a25be217f9a2c 100644
--- a/arch/x86/kernel/fpu/signal.c
+++ b/arch/x86/kernel/fpu/signal.c
@@ -156,7 +156,16 @@ int copy_fpstate_to_sigframe(void __user *buf, void __user *buf_fx, int size)
sizeof(struct user_i387_ia32_struct), NULL,
(struct _fpstate_32 __user *) buf) ? -1 : 1;

- copy_fpregs_to_fpstate(fpu);
+ __fpregs_changes_begin();
+ /*
+ * If we do not need to load the FPU registers at return to userspace
+ * then the CPU has the current state and we need to save it. Otherwise
+ * it is already done and we can skip it.
+ */
+ if (!test_thread_flag(TIF_NEED_FPU_LOAD))
+ copy_fpregs_to_fpstate(fpu);
+
+ __fpregs_changes_end();

if (using_compacted_format()) {
copy_xstate_to_user(buf_fx, xsave, 0, size);
--
2.20.1