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From: Thomas Gleixner <tglx@linutronix.de>
To: LKML <linux-kernel@vger.kernel.org>
Cc: x86@kernel.org, "Chang S. Bae" <chang.seok.bae@intel.com>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	Arjan van de Ven <arjan@linux.intel.com>,
	kvm@vger.kernel.org, Paolo Bonzini <pbonzini@redhat.com>,
	"Liu, Jing2" <jing2.liu@intel.com>,
	Sean Christopherson <seanjc@google.com>,
	Xiaoyao Li <xiaoyao.li@intel.com>
Subject: [patch V2 02/30] x86/fpu: Update stale comments
Date: Fri, 15 Oct 2021 03:15:56 +0200 (CEST)	[thread overview]
Message-ID: <20211015011538.493570236@linutronix.de> (raw)
In-Reply-To: 20211015011411.304289784@linutronix.de

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@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 37dbfed29d75..64f0d4eda0b0 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);
 	}


  parent reply	other threads:[~2021-10-15  1:16 UTC|newest]

Thread overview: 62+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-10-15  1:15 [patch V2 00/30] x86/fpu: Preparatory cleanups for AMX support (part 1) Thomas Gleixner
2021-10-15  1:15 ` [patch V2 01/30] x86/fpu: Remove pointless argument from switch_fpu_finish() Thomas Gleixner
2021-10-20 13:44   ` [tip: x86/fpu] " tip-bot2 for Thomas Gleixner
2021-10-15  1:15 ` Thomas Gleixner [this message]
2021-10-20 13:44   ` [tip: x86/fpu] x86/fpu: Update stale comments tip-bot2 for Thomas Gleixner
2021-10-15  1:15 ` [patch V2 03/30] x86/pkru: Remove useless include Thomas Gleixner
2021-10-20 13:44   ` [tip: x86/fpu] " tip-bot2 for Thomas Gleixner
2021-10-15  1:15 ` [patch V2 04/30] x86/fpu: Restrict xsaves()/xrstors() to independent states Thomas Gleixner
2021-10-20 13:44   ` [tip: x86/fpu] " tip-bot2 for Thomas Gleixner
2021-10-15  1:16 ` [patch V2 05/30] x86/fpu: Cleanup the on_boot_cpu clutter Thomas Gleixner
2021-10-20 13:44   ` [tip: x86/fpu] " tip-bot2 for Thomas Gleixner
2021-10-15  1:16 ` [patch V2 06/30] x86/fpu: Remove pointless memset in fpu_clone() Thomas Gleixner
2021-10-20 13:44   ` [tip: x86/fpu] " tip-bot2 for Thomas Gleixner
2021-10-15  1:16 ` [patch V2 07/30] x86/process: Clone FPU in copy_thread() Thomas Gleixner
2021-10-20 13:44   ` [tip: x86/fpu] " tip-bot2 for Thomas Gleixner
2021-10-15  1:16 ` [patch V2 08/30] x86/fpu: Do not inherit FPU context for kernel and IO worker threads Thomas Gleixner
2021-10-20 13:44   ` [tip: x86/fpu] " tip-bot2 for Thomas Gleixner
2021-10-15  1:16 ` [patch V2 09/30] x86/fpu: Cleanup xstate xcomp_bv initialization Thomas Gleixner
2021-10-20 13:44   ` [tip: x86/fpu] " tip-bot2 for Thomas Gleixner
2021-10-15  1:16 ` [patch V2 10/30] x86/fpu/xstate: Provide and use for_each_xfeature() Thomas Gleixner
2021-10-20 13:44   ` [tip: x86/fpu] " tip-bot2 for Thomas Gleixner
2021-10-15  1:16 ` [patch V2 11/30] x86/fpu/xstate: Mark all init only functions __init Thomas Gleixner
2021-10-20 13:44   ` [tip: x86/fpu] " tip-bot2 for Thomas Gleixner
2021-10-15  1:16 ` [patch V2 12/30] x86/fpu: Move KVMs FPU swapping to FPU core Thomas Gleixner
2021-10-20 13:44   ` [tip: x86/fpu] " tip-bot2 for Thomas Gleixner
2021-10-15  1:16 ` [patch V2 13/30] x86/fpu: Replace KVMs home brewed FPU copy from user Thomas Gleixner
2021-10-20 13:44   ` [tip: x86/fpu] " tip-bot2 for Thomas Gleixner
2021-10-15  1:16 ` [patch V2 14/30] x86/fpu: Rework copy_xstate_to_uabi_buf() Thomas Gleixner
2021-10-20 13:44   ` [tip: x86/fpu] " tip-bot2 for Thomas Gleixner
2021-10-15  1:16 ` [patch V2 15/30] x86/fpu: Replace KVMs home brewed FPU copy to user Thomas Gleixner
2021-10-21 15:12   ` [tip: x86/fpu] " tip-bot2 for Thomas Gleixner
2021-10-15  1:16 ` [patch V2 16/30] x86/fpu: Mark fpu__init_prepare_fx_sw_frame() as __init Thomas Gleixner
2021-10-20 13:44   ` [tip: x86/fpu] " tip-bot2 for Thomas Gleixner
2021-10-15  1:16 ` [patch V2 17/30] x86/fpu: Move context switch and exit to user inlines into sched.h Thomas Gleixner
2021-10-20 13:44   ` [tip: x86/fpu] " tip-bot2 for Thomas Gleixner
2021-10-15  1:16 ` [patch V2 18/30] x86/fpu: Clean up cpu feature tests Thomas Gleixner
2021-10-20 13:44   ` [tip: x86/fpu] x86/fpu: Clean up CPU " tip-bot2 for Thomas Gleixner
2021-10-15  1:16 ` [patch V2 19/30] x86/fpu: Make os_xrstor_booting() private Thomas Gleixner
2021-10-20 13:44   ` [tip: x86/fpu] " tip-bot2 for Thomas Gleixner
2021-10-15  1:16 ` [patch V2 20/30] x86/fpu: Move os_xsave() and os_xrstor() to core Thomas Gleixner
2021-10-20 13:44   ` [tip: x86/fpu] " tip-bot2 for Thomas Gleixner
2021-10-15  1:16 ` [patch V2 21/30] x86/fpu: Move legacy ASM wrappers " Thomas Gleixner
2021-10-20 13:44   ` [tip: x86/fpu] " tip-bot2 for Thomas Gleixner
2021-10-15  1:16 ` [patch V2 22/30] x86/fpu: Make WARN_ON_FPU() private Thomas Gleixner
2021-10-20 13:44   ` [tip: x86/fpu] " tip-bot2 for Thomas Gleixner
2021-10-15  1:16 ` [patch V2 23/30] x86/fpu: Move fpregs_restore_userregs() to core Thomas Gleixner
2021-10-19 18:11   ` Borislav Petkov
2021-10-20 13:44   ` [tip: x86/fpu] " tip-bot2 for Thomas Gleixner
2021-10-15  1:16 ` [patch V2 24/30] x86/fpu: Move mxcsr related code " Thomas Gleixner
2021-10-20 13:44   ` [tip: x86/fpu] " tip-bot2 for Thomas Gleixner
2021-10-15  1:16 ` [patch V2 25/30] x86/fpu: Move fpstate functions to api.h Thomas Gleixner
2021-10-20 13:44   ` [tip: x86/fpu] " tip-bot2 for Thomas Gleixner
2021-10-15  1:16 ` [patch V2 26/30] x86/fpu: Remove internal.h dependency from fpu/signal.h Thomas Gleixner
2021-10-20 13:44   ` [tip: x86/fpu] " tip-bot2 for Thomas Gleixner
2021-10-15  1:16 ` [patch V2 27/30] x86/sev: Include fpu/xcr.h Thomas Gleixner
2021-10-20 13:44   ` [tip: x86/fpu] " tip-bot2 for Thomas Gleixner
2021-10-15  1:16 ` [patch V2 28/30] x86/fpu: Mop up the internal.h leftovers Thomas Gleixner
2021-10-20 13:44   ` [tip: x86/fpu] " tip-bot2 for Thomas Gleixner
2021-10-15  1:16 ` [patch V2 29/30] x86/fpu: Replace the includes of fpu/internal.h Thomas Gleixner
2021-10-20 13:44   ` [tip: x86/fpu] " tip-bot2 for Thomas Gleixner
2021-10-15  1:16 ` [patch V2 30/30] x86/fpu: Provide a proper function for ex_handler_fprestore() Thomas Gleixner
2021-10-20 13:44   ` [tip: x86/fpu] " tip-bot2 for Thomas Gleixner

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