Re: [PATCH 4/4] x86/fpu: don't abuse drop_init_fpu() in flush_thread()

[Borislav Petkov <bp@suse.de>]

On Sun, Mar 15, 2015 at 09:38:16PM +0100, Borislav Petkov wrote:
> How about we call this function fpu_reset_state() instead?

IOW, something like this. Reading the usage sites actually make much
more sense to me now. It could be just me though...

:-)

---
From: Borislav Petkov <bp@suse.de>
Date: Mon, 16 Mar 2015 10:21:55 +0100
Subject: [PATCH] x86/fpu: Rename drop_init_fpu() to fpu_reset_state()

Call it what it does and in accordance with the context where it is
used: we reset the FPU state either because we were unable to restore it
from the one saved in the task or because we simply want to reset it.

Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Ingo Molnar <mingo@kernel.org>
---
 arch/x86/include/asm/fpu-internal.h | 8 ++++++--
 arch/x86/kernel/i387.c              | 2 +-
 arch/x86/kernel/signal.c            | 2 +-
 arch/x86/kernel/traps.c             | 2 +-
 arch/x86/kernel/xsave.c             | 4 ++--
 5 files changed, 11 insertions(+), 7 deletions(-)

diff --git a/arch/x86/include/asm/fpu-internal.h b/arch/x86/include/asm/fpu-internal.h
index 2d4adff428ac..da5e96756570 100644
--- a/arch/x86/include/asm/fpu-internal.h
+++ b/arch/x86/include/asm/fpu-internal.h
@@ -406,7 +406,11 @@ static inline void restore_init_xstate(void)
 		fxrstor_checking(&init_xstate_buf->i387);
 }
 
-static inline void drop_init_fpu(struct task_struct *tsk)
+/*
+ * Reset the FPU state in the eager case and drop it in the lazy case (later use
+ * will reinit it).
+ */
+static inline void fpu_reset_state(struct task_struct *tsk)
 {
 	if (!use_eager_fpu())
 		drop_fpu(tsk);
@@ -480,7 +484,7 @@ static inline void switch_fpu_finish(struct task_struct *new, fpu_switch_t fpu)
 {
 	if (fpu.preload) {
 		if (unlikely(restore_fpu_checking(new)))
-			drop_init_fpu(new);
+			fpu_reset_state(new);
 	}
 }
 
diff --git a/arch/x86/kernel/i387.c b/arch/x86/kernel/i387.c
index 29e982ada854..41575b9b1021 100644
--- a/arch/x86/kernel/i387.c
+++ b/arch/x86/kernel/i387.c
@@ -108,7 +108,7 @@ void __kernel_fpu_end(void)
 
 	if (__thread_has_fpu(me)) {
 		if (WARN_ON(restore_fpu_checking(me)))
-			drop_init_fpu(me);
+			fpu_reset_state(me);
 	} else if (!use_eager_fpu()) {
 		stts();
 	}
diff --git a/arch/x86/kernel/signal.c b/arch/x86/kernel/signal.c
index e5042463c1bc..59eaae6185e2 100644
--- a/arch/x86/kernel/signal.c
+++ b/arch/x86/kernel/signal.c
@@ -679,7 +679,7 @@ handle_signal(struct ksignal *ksig, struct pt_regs *regs)
 		 * Ensure the signal handler starts with the new fpu state.
 		 */
 		if (used_math())
-			drop_init_fpu(current);
+			fpu_reset_state(current);
 	}
 	signal_setup_done(failed, ksig, test_thread_flag(TIF_SINGLESTEP));
 }
diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
index 92b83e299ed3..156d75859466 100644
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -863,7 +863,7 @@ void math_state_restore(void)
 	kernel_fpu_disable();
 	__thread_fpu_begin(tsk);
 	if (unlikely(restore_fpu_checking(tsk))) {
-		drop_init_fpu(tsk);
+		fpu_reset_state(tsk);
 		force_sig_info(SIGSEGV, SEND_SIG_PRIV, tsk);
 	} else {
 		tsk->thread.fpu_counter++;
diff --git a/arch/x86/kernel/xsave.c b/arch/x86/kernel/xsave.c
index 0bf82c5ac529..65c29b070e09 100644
--- a/arch/x86/kernel/xsave.c
+++ b/arch/x86/kernel/xsave.c
@@ -342,7 +342,7 @@ int __restore_xstate_sig(void __user *buf, void __user *buf_fx, int size)
 			 config_enabled(CONFIG_IA32_EMULATION));
 
 	if (!buf) {
-		drop_init_fpu(tsk);
+		fpu_reset_state(tsk);
 		return 0;
 	}
 
@@ -416,7 +416,7 @@ int __restore_xstate_sig(void __user *buf, void __user *buf_fx, int size)
 		 */
 		user_fpu_begin();
 		if (restore_user_xstate(buf_fx, xstate_bv, fx_only)) {
-			drop_init_fpu(tsk);
+			fpu_reset_state(tsk);
 			return -1;
 		}
 	}
-- 
2.3.3

-- 
Regards/Gruss,
    Boris.

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