linux-kernel - [tip: x86/fpu] x86/fpu: Update stale comments

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Date:   Wed, 20 Oct 2021 13:44:45 -0000
From:   "tip-bot2 for Thomas Gleixner" <tip-bot2@...utronix.de>
To:     linux-tip-commits@...r.kernel.org
Cc:     Thomas Gleixner <tglx@...utronix.de>, Borislav Petkov <bp@...e.de>,
        x86@...nel.org, linux-kernel@...r.kernel.org
Subject: [tip: x86/fpu] x86/fpu: Update stale comments

The following commit has been merged into the x86/fpu branch of tip:

Commit-ID:     d2d926482cdfbd5517826eca4e39dcd8757f04d3
Gitweb:        https://git.kernel.org/tip/d2d926482cdfbd5517826eca4e39dcd8757f04d3
Author:        Thomas Gleixner <tglx@...utronix.de>
AuthorDate:    Fri, 15 Oct 2021 03:15:56 +02:00
Committer:     Borislav Petkov <bp@...e.de>
CommitterDate: Wed, 20 Oct 2021 15:27:25 +02:00

x86/fpu: Update stale comments

copy_fpstate_to_sigframe() does not have a slow path anymore. Neither does
the !ia32 restore in __fpu_restore_sig().

Update the comments accordingly.

Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Signed-off-by: Borislav Petkov <bp@...e.de>
Link: https://lkml.kernel.org/r/20211015011538.493570236@linutronix.de
---
 arch/x86/kernel/fpu/signal.c | 13 +++----------
 1 file changed, 3 insertions(+), 10 deletions(-)

diff --git a/arch/x86/kernel/fpu/signal.c b/arch/x86/kernel/fpu/signal.c
index 51c4915..e257805 100644
--- a/arch/x86/kernel/fpu/signal.c
+++ b/arch/x86/kernel/fpu/signal.c
@@ -155,10 +155,8 @@ static inline int copy_fpregs_to_sigframe(struct xregs_state __user *buf)
  *	buf == buf_fx for 64-bit frames and 32-bit fsave frame.
  *	buf != buf_fx for 32-bit frames with fxstate.
  *
- * Try to save it directly to the user frame with disabled page fault handler.
- * If this fails then do the slow path where the FPU state is first saved to
- * task's fpu->state and then copy it to the user frame pointed to by the
- * aligned pointer 'buf_fx'.
+ * Save it directly to the user frame with disabled page fault handler. If
+ * that faults, try to clear the frame which handles the page fault.
  *
  * If this is a 32-bit frame with fxstate, put a fsave header before
  * the aligned state at 'buf_fx'.
@@ -334,12 +332,7 @@ static bool __fpu_restore_sig(void __user *buf, void __user *buf_fx,
 	}
 
 	if (likely(!ia32_fxstate)) {
-		/*
-		 * Attempt to restore the FPU registers directly from user
-		 * memory. For that to succeed, the user access cannot cause page
-		 * faults. If it does, fall back to the slow path below, going
-		 * through the kernel buffer with the enabled pagefault handler.
-		 */
+		/* Restore the FPU registers directly from user memory. */
 		return restore_fpregs_from_user(buf_fx, user_xfeatures, fx_only,
 						state_size);
 	}