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[PATCH 4.12 99/99] powerpc/mm: Ensure cpumask update is ordered

From Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Newsgroups linux.kernel
Subject [PATCH 4.12 99/99] powerpc/mm: Ensure cpumask update is ordered
Date 2017-08-28 10:20 +0200
Message-ID <ujnr8-3du-101@gated-at.bofh.it> (permalink)
References <ujnhn-38X-3@gated-at.bofh.it>
Organization linux.* mail to news gateway

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

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

From: Benjamin Herrenschmidt <benh@kernel.crashing.org>

commit 1a92a80ad386a1a6e3b36d576d52a1a456394b70 upstream.

There is no guarantee that the various isync's involved with
the context switch will order the update of the CPU mask with
the first TLB entry for the new context being loaded by the HW.

Be safe here and add a memory barrier to order any subsequent
load/store which may bring entries into the TLB.

The corresponding barrier on the other side already exists as
pte updates use pte_xchg() which uses __cmpxchg_u64 which has
a sync after the atomic operation.

Cc: stable@vger.kernel.org
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Reviewed-by: Nicholas Piggin <npiggin@gmail.com>
[mpe: Add comments in the code]
[mpe: Backport to 4.12, minor context change]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 arch/powerpc/include/asm/mmu_context.h      |   20 +++++++++++++++++++-
 arch/powerpc/include/asm/pgtable-be-types.h |    1 +
 arch/powerpc/include/asm/pgtable-types.h    |    1 +
 3 files changed, 21 insertions(+), 1 deletion(-)

--- a/arch/powerpc/include/asm/mmu_context.h
+++ b/arch/powerpc/include/asm/mmu_context.h
@@ -80,9 +80,27 @@ static inline void switch_mm_irqs_off(st
 				      struct task_struct *tsk)
 {
 	/* Mark this context has been used on the new CPU */
-	if (!cpumask_test_cpu(smp_processor_id(), mm_cpumask(next)))
+	if (!cpumask_test_cpu(smp_processor_id(), mm_cpumask(next))) {
 		cpumask_set_cpu(smp_processor_id(), mm_cpumask(next));
 
+		/*
+		 * This full barrier orders the store to the cpumask above vs
+		 * a subsequent operation which allows this CPU to begin loading
+		 * translations for next.
+		 *
+		 * When using the radix MMU that operation is the load of the
+		 * MMU context id, which is then moved to SPRN_PID.
+		 *
+		 * For the hash MMU it is either the first load from slb_cache
+		 * in switch_slb(), and/or the store of paca->mm_ctx_id in
+		 * copy_mm_to_paca().
+		 *
+		 * On the read side the barrier is in pte_xchg(), which orders
+		 * the store to the PTE vs the load of mm_cpumask.
+		 */
+		smp_mb();
+	}
+
 	/* 32-bit keeps track of the current PGDIR in the thread struct */
 #ifdef CONFIG_PPC32
 	tsk->thread.pgdir = next->pgd;
--- a/arch/powerpc/include/asm/pgtable-be-types.h
+++ b/arch/powerpc/include/asm/pgtable-be-types.h
@@ -87,6 +87,7 @@ static inline bool pte_xchg(pte_t *ptep,
 	unsigned long *p = (unsigned long *)ptep;
 	__be64 prev;
 
+	/* See comment in switch_mm_irqs_off() */
 	prev = (__force __be64)__cmpxchg_u64(p, (__force unsigned long)pte_raw(old),
 					     (__force unsigned long)pte_raw(new));
 
--- a/arch/powerpc/include/asm/pgtable-types.h
+++ b/arch/powerpc/include/asm/pgtable-types.h
@@ -62,6 +62,7 @@ static inline bool pte_xchg(pte_t *ptep,
 {
 	unsigned long *p = (unsigned long *)ptep;
 
+	/* See comment in switch_mm_irqs_off() */
 	return pte_val(old) == __cmpxchg_u64(p, pte_val(old), pte_val(new));
 }
 #endif

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[PATCH 4.12 00/99] 4.12.10-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 10:10 +0200
  [PATCH 4.12 90/99] iio: magnetometer: st_magn: fix status register address for LSM303AGR Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 10:10 +0200
  [PATCH 4.12 23/99] irda: do not leak initialized list.dev to userspace Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 10:10 +0200
  [PATCH 4.12 40/99] ALSA: firewire: fix NULL pointer dereference when releasing uninitialized data of iso-resource Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 10:10 +0200
  [PATCH 4.12 38/99] ALSA: core: Fix unexpected error at replacing user TLV Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 10:10 +0200
  [PATCH 4.12 20/99] ipv6: repair fib6 tree in failure case Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 10:10 +0200
  [PATCH 4.12 44/99] ARCv2: PAE40: set MSB even if !CONFIG_ARC_HAS_PAE40 but PAE exists in SoC Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 10:10 +0200
  [PATCH 4.12 17/99] sctp: fully initialize the IPv6 address in sctp_v6_to_addr() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 10:10 +0200
  [PATCH 4.12 68/99] cifs: Fix df output for users with quota limits Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 10:10 +0200
  [PATCH 4.12 11/99] net: igmp: Use ingress interface rather than vrf device Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 10:10 +0200
  [PATCH 4.12 18/99] tipc: fix use-after-free Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 10:10 +0200
  [PATCH 4.12 13/99] ptr_ring: use kmalloc_array() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 10:10 +0200
  [PATCH 4.12 36/99] KVM: x86: block guest protection keys unless the host has them enabled Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 10:10 +0200
  [PATCH 4.12 31/99] Input: ALPS - fix two-finger scroll breakage in right side on ALPS touchpad Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 10:10 +0200
  [PATCH 4.12 10/99] bpf: fix bpf_trace_printk on 32 bit archs Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 10:10 +0200
  [PATCH 4.12 93/99] iommu: Fix wrong freeing of iommu_device->dev Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 10:20 +0200
  [PATCH 4.12 75/99] timers: Fix excessive granularity of new timers after a nohz idle Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 10:20 +0200
  [PATCH 4.12 79/99] netfilter: nat: fix src map lookup Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 10:20 +0200
  [PATCH 4.12 77/99] net: sunrpc: svcsock: fix NULL-pointer exception Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 10:20 +0200
  [PATCH 4.12 99/99] powerpc/mm: Ensure cpumask update is ordered Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 10:20 +0200
  [PATCH 4.12 81/99] Bluetooth: hidp: fix possible might sleep error in hidp_session_thread Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 10:20 +0200
  [PATCH 4.12 91/99] iio: magnetometer: st_magn: remove ihl property for LSM303AGR Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 11:10 +0200
  [PATCH 4.12 76/99] x86/mm: Fix use-after-free of ldt_struct Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 11:10 +0200
  [PATCH 4.12 80/99] netfilter: nfnetlink: Improve input length sanitization in nfnetlink_rcv Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 11:10 +0200
  [PATCH 4.12 69/99] cifs: return ENAMETOOLONG for overlong names in cifs_open()/cifs_lookup() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 11:10 +0200
  [PATCH 4.12 96/99] ntb: transport shouldnt disable link due to bogus values in SPADs Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 11:10 +0200
  [PATCH 4.12 89/99] iio: hid-sensor-trigger: Fix the race with user space powering up sensors Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 11:10 +0200
  [PATCH 4.12 73/99] ftrace: Check for null ret_stack on profile function graph entry function Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 11:10 +0200
  [PATCH 4.12 95/99] ntb: ntb_test: ensure the link is up before trying to configure the mws Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 11:10 +0200
  [PATCH 4.12 63/99] tracing: Missing error code in tracer_alloc_buffers() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 11:10 +0200
  [PATCH 4.12 82/99] Bluetooth: cmtp: fix possible might sleep error in cmtp_session Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 11:10 +0200
  [PATCH 4.12 94/99] Clarify (and fix) MAX_LFS_FILESIZE macros Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 11:10 +0200
  [PATCH 4.12 74/99] perf/core: Fix group {cpu,task} validation Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 11:10 +0200
  [PATCH 4.12 71/99] ring-buffer: Have ring_buffer_alloc_read_page() return error on offline CPU Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 11:10 +0200
  [PATCH 4.12 35/99] KVM, pkeys: do not use PKRU value in vcpu->arch.guest_fpu.state Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 11:10 +0200
  [PATCH 4.12 83/99] Bluetooth: bnep: fix possible might sleep error in bnep_session Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 11:10 +0200
  [PATCH 4.12 72/99] virtio_pci: fix cpu affinity support Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 11:10 +0200
  [PATCH 4.12 97/99] ACPI: APD: Fix HID for Hisilicon Hip07/08 Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 11:10 +0200
  [PATCH 4.12 87/99] ANDROID: binder: fix proc->tsk check. Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 11:10 +0200
  [PATCH 4.12 37/99] ALSA: usb-audio: Add delay quirk for H650e/Jabra 550a USB headsets Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 11:10 +0200
  [PATCH 4.12 85/99] binder: use group leader instead of open thread Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 11:10 +0200
  [PATCH 4.12 78/99] netfilter: expect: fix crash when putting uninited expectation Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 11:10 +0200
  [PATCH 4.12 98/99] ACPI: EC: Fix regression related to wrong ECDT initialization order Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 11:10 +0200
  [PATCH 4.12 70/99] nfsd: Limit end of page list when decoding NFSv4 WRITE Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 11:10 +0200
  [PATCH 4.12 39/99] ALSA: hda - Add stereo mic quirk for Lenovo G50-70 (17aa:3978) Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 11:10 +0200
  [PATCH 4.12 33/99] KVM: s390: sthyi: fix specification exception detection Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 11:20 +0200
  [PATCH 4.12 64/99] tracing: Fix kmemleak in tracing_map_array_free() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 11:20 +0200
  [PATCH 4.12 52/99] arm64: fpsimd: Prevent registers leaking across exec Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 11:20 +0200
  [PATCH 4.12 03/99] bonding: ratelimit failed speed/duplex update warning Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 11:20 +0200
  [PATCH 4.12 07/99] ipv4: fix NULL dereference in free_fib_info_rcu() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 11:20 +0200
  [PATCH 4.12 47/99] dax: fix deadlock due to misaligned PMD faults Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 11:20 +0200
  [PATCH 4.12 57/99] drm/atomic: If the atomic check fails, return its value first Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 11:20 +0200
  [PATCH 4.12 45/99] PM/hibernate: touch NMI watchdog when creating snapshot Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 11:20 +0200
  [PATCH 4.12 43/99] ARCv2: PAE40: Explicitly set MSB counterpart of SLC region ops addresses Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 11:20 +0200
  [PATCH 4.12 08/99] net_sched/sfq: update hierarchical backlog when drop packet Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 11:20 +0200
  [PATCH 4.12 61/99] ACPI: device property: Fix node lookup in acpi_graph_get_child_prop_value() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 11:20 +0200
  [PATCH 4.12 48/99] i2c: designware: Fix system suspend Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 11:20 +0200
  [PATCH 4.12 66/99] RDMA/uverbs: Initialize cq_context appropriately Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 11:20 +0200
  [PATCH 4.12 30/99] Input: elan_i2c - add ELAN0602 ACPI ID to support Lenovo Yoga310 Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 11:20 +0200
  [PATCH 4.12 46/99] mm, shmem: fix handling /sys/kernel/mm/transparent_hugepage/shmem_enabled Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 11:20 +0200
  [PATCH 4.12 60/99] Revert "drm/amdgpu: fix vblank_time when displays are off" Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 11:20 +0200
  [PATCH 4.12 32/99] KVM: s390: sthyi: fix sthyi inline assembly Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 11:20 +0200
  [PATCH 4.12 09/99] net_sched: remove warning from qdisc_hash_add Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 11:20 +0200
  [PATCH 4.12 65/99] tracing: Fix freeing of filter in create_filter() when set_str is false Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 11:20 +0200
  [PATCH 4.12 41/99] ALSA: firewire-motu: destroy stream data surely at failure of card initialization Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 11:20 +0200
  [PATCH 4.12 05/99] dccp: purge write queue in dccp_destroy_sock() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 11:20 +0200
  [PATCH 4.12 42/99] ARCv2: SLC: Make sure busy bit is set properly for region ops Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 11:20 +0200
  [PATCH 4.12 49/99] mm/madvise.c: fix freeing of locked page with MADV_FREE Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 11:20 +0200
  [PATCH 4.12 21/99] tcp: when rearming RTO, if RTO time is in past then fire RTO ASAP Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 11:30 +0200
  [PATCH 4.12 12/99] openvswitch: fix skb_panic due to the incorrect actions attrlen Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 11:30 +0200
  [PATCH 4.12 16/99] tun: handle register_netdevice() failures properly Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 11:30 +0200
  [PATCH 4.12 24/99] net: sched: fix NULL pointer dereference when action calls some targets Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 11:30 +0200
  [PATCH 4.12 02/99] bonding: require speed/duplex only for 802.3ad, alb and tlb Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 11:30 +0200
  [PATCH 4.12 28/99] bpf/verifier: fix min/max handling in BPF_SUB Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 11:30 +0200
  [PATCH 4.12 26/99] bpf, verifier: add additional patterns to evaluate_reg_imm_alu Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 11:30 +0200
  [PATCH 4.12 14/99] ipv4: better IP_MAX_MTU enforcement Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 11:30 +0200
  [PATCH 4.12 19/99] ipv6: reset fn->rr_ptr when replacing route Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-28 11:30 +0200
  Re: [PATCH 4.12 00/99] 4.12.10-stable review Shuah Khan <shuahkh@osg.samsung.com> - 2017-08-28 21:50 +0200
    Re: [PATCH 4.12 00/99] 4.12.10-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-29 07:00 +0200
  Re: [PATCH 4.12 00/99] 4.12.10-stable review Guenter Roeck <linux@roeck-us.net> - 2017-08-29 02:20 +0200
    Re: [PATCH 4.12 00/99] 4.12.10-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-29 07:00 +0200

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