Patch "x86/smpboot: Remove stale TLB flush invocations" has been added to the 4.4-stable tree

This is a note to let you know that I've just added the patch titled

x86/smpboot: Remove stale TLB flush invocations

to the 4.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
x86-smpboot-remove-stale-tlb-flush-invocations.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Thomas Gleixner <[email protected]>
Date: Sat, 30 Dec 2017 22:13:53 +0100
Subject: x86/smpboot: Remove stale TLB flush invocations

From: Thomas Gleixner <[email protected]>

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.

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

@@ -104,14 +104,10 @@ 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)

@@ -119,11 +115,6 @@ 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.
 	 */

Patches currently in stable-queue which might be from [email protected] are

queue-4.4/nohz-prevent-a-timer-interrupt-storm-in-tick_nohz_stop_sched_tick.patch queue-4.4/x86-vm86-32-switch-to-flush_tlb_mm_range-in-mark_screen_rdonly.patch queue-4.4/x86-mm-add-the-nopcid-boot-option-to-turn-off-pcid.patch queue-4.4/x86-mm-enable-cr4.pcide-on-supported-systems.patch queue-4.4/pci-pm-force-devices-to-d0-in-pci_pm_thaw_noirq.patch queue-4.4/x86-smpboot-remove-stale-tlb-flush-invocations.patch queue-4.4/x86-mm-remove-the-up-asm-tlbflush.h-code-always-use-the-formerly-smp-code.patch queue-4.4/x86-mm-reimplement-flush_tlb_page-using-flush_tlb_mm_range.patch queue-4.4/x86-mm-make-flush_tlb_mm_range-more-predictable.patch queue-4.4/x86-mm-remove-flush_tlb-and-flush_tlb_current_task.patch queue-4.4/x86-mm-disable-pcid-on-32-bit-kernels.patch queue-4.4/x86-mm-64-fix-reboot-interaction-with-cr4.pcide.patch