linux-kernel - [PATCH 4.9 73/75] x86/smpboot: Remove stale TLB flush invocations

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Date:   Mon,  1 Jan 2018 15:32:50 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Dominik Brodowski <linux@...inikbrodowski.net>,
        Thomas Gleixner <tglx@...utronix.de>,
        Andy Lutomirski <luto@...nel.org>,
        Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Linus Torvalds <torvalds@...uxfoundation.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...nel.org>
Subject: [PATCH 4.9 73/75] x86/smpboot: Remove stale TLB flush invocations

4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Thomas Gleixner <tglx@...utronix.de>

commit 322f8b8b340c824aef891342b0f5795d15e11562 upstream.

smpboot_setup_warm_reset_vector() and smpboot_restore_warm_reset_vector()
invoke local_flush_tlb() for no obvious reason.

Digging in history revealed that the original code in the 2.1 era added
those because the code manipulated a swapper_pg_dir pagetable entry. The
pagetable manipulation was removed long ago in the 2.3 timeframe, but the
TLB flush invocations stayed around forever.

Remove them along with the pointless pr_debug()s which come from the same 2.1
change.

Reported-by: Dominik Brodowski <linux@...inikbrodowski.net>
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Cc: Andy Lutomirski <luto@...nel.org>
Cc: Borislav Petkov <bp@...en8.de>
Cc: Dave Hansen <dave.hansen@...ux.intel.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Linus Torvalds <torvalds@...uxfoundation.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Link: http://lkml.kernel.org/r/20171230211829.586548655@linutronix.de
Signed-off-by: Ingo Molnar <mingo@...nel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 arch/x86/kernel/smpboot.c |    9 ---------
 1 file changed, 9 deletions(-)

--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -115,14 +115,10 @@ static inline void smpboot_setup_warm_re
 	spin_lock_irqsave(&rtc_lock, flags);
 	CMOS_WRITE(0xa, 0xf);
 	spin_unlock_irqrestore(&rtc_lock, flags);
-	local_flush_tlb();
-	pr_debug("1.\n");
 	*((volatile unsigned short *)phys_to_virt(TRAMPOLINE_PHYS_HIGH)) =
 							start_eip >> 4;
-	pr_debug("2.\n");
 	*((volatile unsigned short *)phys_to_virt(TRAMPOLINE_PHYS_LOW)) =
 							start_eip & 0xf;
-	pr_debug("3.\n");
 }
 
 static inline void smpboot_restore_warm_reset_vector(void)
@@ -130,11 +126,6 @@ static inline void smpboot_restore_warm_
 	unsigned long flags;
 
 	/*
-	 * Install writable page 0 entry to set BIOS data area.
-	 */
-	local_flush_tlb();
-
-	/*
 	 * Paranoid:  Set warm reset code and vector here back
 	 * to default values.
 	 */