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[PATCH 3.14 14/79] x86/apic: Serialize LVTT and TSC_DEADLINE writes

From Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Newsgroups linux.kernel
Subject [PATCH 3.14 14/79] x86/apic: Serialize LVTT and TSC_DEADLINE writes
Date 2015-10-18 05:30 +0200
Message-ID <qkMPw-19j-5@gated-at.bofh.it> (permalink)
References <qkMw9-KI-3@gated-at.bofh.it>
Organization linux.* mail to news gateway

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

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

From: Shaohua Li <shli@fb.com>

commit 5d7c631d926b59aa16f3c56eaeb83f1036c81dc7 upstream.

The APIC LVTT register is MMIO mapped but the TSC_DEADLINE register is an
MSR. The write to the TSC_DEADLINE MSR is not serializing, so it's not
guaranteed that the write to LVTT has reached the APIC before the
TSC_DEADLINE MSR is written. In such a case the write to the MSR is
ignored and as a consequence the local timer interrupt never fires.

The SDM decribes this issue for xAPIC and x2APIC modes. The
serialization methods recommended by the SDM differ.

xAPIC:
 "1. Memory-mapped write to LVT Timer Register, setting bits 18:17 to 10b.
  2. WRMSR to the IA32_TSC_DEADLINE MSR a value much larger than current time-stamp counter.
  3. If RDMSR of the IA32_TSC_DEADLINE MSR returns zero, go to step 2.
  4. WRMSR to the IA32_TSC_DEADLINE MSR the desired deadline."

x2APIC:
 "To allow for efficient access to the APIC registers in x2APIC mode,
  the serializing semantics of WRMSR are relaxed when writing to the
  APIC registers. Thus, system software should not use 'WRMSR to APIC
  registers in x2APIC mode' as a serializing instruction. Read and write
  accesses to the APIC registers will occur in program order. A WRMSR to
  an APIC register may complete before all preceding stores are globally
  visible; software can prevent this by inserting a serializing
  instruction, an SFENCE, or an MFENCE before the WRMSR."

The xAPIC method is to just wait for the memory mapped write to hit
the LVTT by checking whether the MSR write has reached the hardware.
There is no reason why a proper MFENCE after the memory mapped write would
not do the same. Andi Kleen confirmed that MFENCE is sufficient for the
xAPIC case as well.

Issue MFENCE before writing to the TSC_DEADLINE MSR. This can be done
unconditionally as all CPUs which have TSC_DEADLINE also have MFENCE
support.

[ tglx: Massaged the changelog ]

Signed-off-by: Shaohua Li <shli@fb.com>
Reviewed-by: Ingo Molnar <mingo@kernel.org>
Cc: <Kernel-team@fb.com>
Cc: <lenb@kernel.org>
Cc: <fenghua.yu@intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Link: http://lkml.kernel.org/r/20150909041352.GA2059853@devbig257.prn2.facebook.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 arch/x86/kernel/apic/apic.c |    7 +++++++
 1 file changed, 7 insertions(+)

--- a/arch/x86/kernel/apic/apic.c
+++ b/arch/x86/kernel/apic/apic.c
@@ -359,6 +359,13 @@ static void __setup_APIC_LVTT(unsigned i
 	apic_write(APIC_LVTT, lvtt_value);
 
 	if (lvtt_value & APIC_LVT_TIMER_TSCDEADLINE) {
+		/*
+		 * See Intel SDM: TSC-Deadline Mode chapter. In xAPIC mode,
+		 * writing to the APIC LVTT and TSC_DEADLINE MSR isn't serialized.
+		 * According to Intel, MFENCE can do the serialization here.
+		 */
+		asm volatile("mfence" : : : "memory");
+
 		printk_once(KERN_DEBUG "TSC deadline timer enabled\n");
 		return;
 	}


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[PATCH 3.14 00/79] 3.14.55-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-18 05:10 +0200
  [PATCH 3.14 50/79] ipvs: do not use random local source address for tunnels Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-18 05:10 +0200
  [PATCH 3.14 69/79] vfs: Test for and handle paths that are unreachable from their mnt_root Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-18 05:10 +0200
  [PATCH 3.14 38/79] netfilter: nf_conntrack: Support expectations in different zones Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-18 05:10 +0200
  [PATCH 3.14 45/79] USB: whiteheat: fix potential null-deref at probe Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-18 05:10 +0200
  [PATCH 3.14 44/79] drm: Reject DRI1 hw lock ioctl functions for kms drivers Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-18 05:10 +0200
  [PATCH 3.14 07/79] perf header: Fixup reading of HEADER_NRCPUS feature Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-18 05:10 +0200
  [PATCH 3.14 54/79] regmap: debugfs: Ensure we dont underflow when printing access masks Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-18 05:10 +0200
  [PATCH 3.14 08/79] hwmon: (nct6775) Swap STEP_UP_TIME and STEP_DOWN_TIME registers for most chips Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-18 05:10 +0200
  [PATCH 3.14 46/79] usb: xhci: Clear XHCI_STATE_DYING on start Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-18 05:10 +0200
  [PATCH 3.14 41/79] disabling oplocks/leases via module parm enable_oplocks broken for SMB3 Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-18 05:10 +0200
  [PATCH 3.14 37/79] dm raid: fix round up of default region size Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-18 05:10 +0200
  [PATCH 3.14 39/79] netfilter: ctnetlink: put back references to master ct and expect objects Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-18 05:10 +0200
  [PATCH 3.14 63/79] staging: comedi: usbduxsigma: dont clobber ao_timer in command test Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-18 05:10 +0200
  [PATCH 3.14 35/79] staging: ion: fix corruption of ion_import_dma_buf Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-18 05:10 +0200
  [PATCH 3.14 49/79] Initialize msg/shm IPC objects before doing ipc_addid() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-18 05:10 +0200
  [PATCH 3.14 70/79] arm64: readahead: fault retry breaks mmap file read random detection Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-18 05:10 +0200
  [PATCH 3.14 48/79] usb: xhci: Add support for URB_ZERO_PACKET to bulk/sg transfers Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-18 05:10 +0200
  [PATCH 3.14 42/79] drm/qxl: only report first monitor as connected if we have no state Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-18 05:10 +0200
  [PATCH 3.14 52/79] cifs: use server timestamp for ntlmv2 authentication Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-18 05:10 +0200
  [PATCH 3.14 68/79] dcache: Handle escaped paths in prepend_path Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-18 05:10 +0200
  [PATCH 3.14 65/79] powerpc/MSI: Fix race condition in tearing down MSI interrupts Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-18 05:10 +0200
  [PATCH 3.14 56/79] security: fix typo in security_task_prctl Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-18 05:20 +0200
  [PATCH 3.14 34/79] dm btree: add ref counting ops for the leaves of top level btrees Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-18 05:20 +0200
  [PATCH 3.14 13/79] dmaengine: dw: properly read DWC_PARAMS register Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-18 05:20 +0200
  [PATCH 3.14 76/79] dm cache: fix NULL pointer when switching from cleaner policy Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-18 05:20 +0200
  [PATCH 3.14 36/79] USB: option: add ZTE PIDs Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-18 05:20 +0200
  [PATCH 3.14 62/79] staging: comedi: usbduxsigma: dont clobber ai_timer in command test Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-18 05:20 +0200
  [PATCH 3.14 04/79] perf tools: Fix copying of /proc/kcore Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-18 05:20 +0200
  [PATCH 3.14 30/79] ASoC: dwc: correct irq clear method Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-18 05:20 +0200
  [PATCH 3.14 53/79] mtd: pxa3xx_nand: add a default chunk size Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-18 05:20 +0200
  [PATCH 3.14 72/79] fib_rules: Fix dump_rules() not to exit early Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-18 05:20 +0200
  [PATCH 3.14 78/79] mm/slab: fix unexpected index mapping result of kmalloc_size(INDEX_NODE+1) Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-18 05:20 +0200
  [PATCH 3.14 06/79] perf stat: Get correct cpu id for print_aggr Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-18 05:20 +0200
  [PATCH 3.14 58/79] usb: Add device quirk for Logitech PTZ cameras Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-18 05:20 +0200
  [PATCH 3.14 74/79] jbd2: avoid infinite loop when destroying aborted journal Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-18 05:20 +0200
  [PATCH 3.14 27/79] ALSA: hda - Apply SPDIF pin ctl to MacBookPro 12,1 Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-18 05:20 +0200
  [PATCH 3.14 55/79] regmap: debugfs: Dont bother actually printing when calculating max length Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-18 05:20 +0200
  [PATCH 3.14 29/79] ASoC: fix broken pxa SoC support Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-18 05:20 +0200
  [PATCH 3.14 59/79] USB: Add reset-resume quirk for two Plantronics usb headphones. Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-18 05:20 +0200
  [PATCH 3.14 33/79] Btrfs: update fix for read corruption of compressed and shared extents Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-18 05:20 +0200
  [PATCH 3.14 61/79] arch,hexagon: Convert smp_mb__*() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-18 05:20 +0200
  [PATCH 3.14 57/79] usb: Use the USB_SS_MULT() macro to get the burst multiplier. Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-18 05:20 +0200
  [PATCH 3.14 09/79] ARM: fix Thumb2 signal handling when ARMv6 is enabled Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-18 05:20 +0200
  [PATCH 3.14 77/79] staging: speakup: fix speakup-r regression Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-18 05:20 +0200
  [PATCH 3.14 05/79] perf hists: Update the column width for the "srcline" sort key Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-18 05:20 +0200
  [PATCH 3.14 32/79] Btrfs: fix read corruption of compressed and shared extents Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-18 05:20 +0200
  [PATCH 3.14 31/79] btrfs: skip waiting on ordered range for special files Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-18 05:20 +0200
  [PATCH 3.14 03/79] iser-target: remove command with state ISTATE_REMOVE Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-18 05:20 +0200
  [PATCH 3.14 75/79] clk: ti: fix dual-registration of uart4_ick Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-18 05:20 +0200
  [PATCH 3.14 25/79] mm: hugetlbfs: skip shared VMAs when unmapping private pages to satisfy a fault Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-18 05:20 +0200
  [PATCH 3.14 71/79] m68k: Define asmlinkage_protect Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-18 05:20 +0200
  [PATCH 3.14 60/79] MIPS: dma-default: Fix 32-bit fall back to GFP_DMA Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-18 05:20 +0200
  [PATCH 3.14 28/79] ASoC: pxa: pxa2xx-ac97: fix dma requestor lines Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-18 05:20 +0200
  [PATCH 3.14 73/79] genirq: Fix race in register_irq_proc() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-18 05:20 +0200
  [PATCH 3.14 10/79] ARM: 8429/1: disable GCC SRA optimization Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-18 05:30 +0200
  [PATCH 3.14 18/79] Use WARN_ON_ONCE for missing X86_FEATURE_NRIPS Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-18 05:30 +0200
  [PATCH 3.14 22/79] sched/core: Fix TASK_DEAD race in finish_task_switch() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-18 05:30 +0200
  [PATCH 3.14 14/79] x86/apic: Serialize LVTT and TSC_DEADLINE writes Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-18 05:30 +0200
  [PATCH 3.14 21/79] x86/xen: Support kexec/kdump in HVM guests by doing a soft reset Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-18 05:30 +0200
  [PATCH 3.14 26/79] ALSA: synth: Fix conflicting OSS device registration on AWE32 Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-18 05:30 +0200
  [PATCH 3.14 01/79] kvm: fix zero length mmio searching Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-18 05:30 +0200
  [PATCH 3.14 20/79] x86/mm: Set NX on gap between __ex_table and rodata Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-18 05:30 +0200
  [PATCH 3.14 12/79] ARM: dts: omap5-uevm.dts: fix i2c5 pinctrl offsets Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-18 05:30 +0200
  [PATCH 3.14 15/79] x86/platform: Fix Geode LX timekeeping in the generic x86 build Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-18 05:30 +0200
  [PATCH 3.14 11/79] windfarm: decrement client count when unregistering Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-18 05:30 +0200
  [PATCH 3.14 23/79] spi: Fix documentation of spi_alloc_master() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-18 05:30 +0200
  [PATCH 3.14 02/79] scsi: fix scsi_error_handler vs. scsi_host_dev_release race Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-18 05:30 +0200
  [PATCH 3.14 17/79] x86/nmi/64: Fix a paravirt stack-clobbering bug in the NMI code Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-18 05:30 +0200
  [PATCH 3.14 24/79] spi: spi-pxa2xx: Check status register to determine if SSSR_TINT is disabled Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-18 05:50 +0200
  [PATCH 3.14 19/79] x86/efi: Fix boot crash by mapping EFI memmap entries bottom-up at runtime, instead of top-down Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-18 05:50 +0200
  Re: [PATCH 3.14 00/79] 3.14.55-stable review Guenter Roeck <linux@roeck-us.net> - 2015-10-19 06:20 +0200
    Re: [PATCH 3.14 00/79] 3.14.55-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-19 17:20 +0200
      Re: [PATCH 3.14 00/79] 3.14.55-stable review Richard Kuo <rkuo@codeaurora.org> - 2015-10-19 21:20 +0200
        Re: [PATCH 3.14 00/79] 3.14.55-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-19 22:10 +0200
          Re: [PATCH 3.14 00/79] 3.14.55-stable review Richard Kuo <rkuo@codeaurora.org> - 2015-10-19 23:40 +0200
  Re: [PATCH 3.14 00/79] 3.14.55-stable review Shuah Khan <shuahkh@osg.samsung.com> - 2015-10-19 17:30 +0200

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