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f86c4fbd93
linux/drivers/irqchip
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Will Deacon f86c4fbd93 irqchip/gic: Ensure ordering between read of INTACK and shared data 
When an IPI is generated by a CPU, the pattern looks roughly like:

  <write shared data>
  smp_wmb();
  <write to GIC to signal SGI>

On the receiving CPU we rely on the fact that, once we've taken the
interrupt, then the freshly written shared data must be visible to us.
Put another way, the CPU isn't going to speculate taking an interrupt.

Unfortunately, this assumption turns out to be broken.

Consider that CPUx wants to send an IPI to CPUy, which will cause CPUy
to read some shared_data. Before CPUx has done anything, a random
peripheral raises an IRQ to the GIC and the IRQ line on CPUy is raised.
CPUy then takes the IRQ and starts executing the entry code, heading
towards gic_handle_irq. Furthermore, let's assume that a bunch of the
previous interrupts handled by CPUy were SGIs, so the branch predictor
kicks in and speculates that irqnr will be <16 and we're likely to
head into handle_IPI. The prefetcher then grabs a speculative copy of
shared_data which contains a stale value.

Meanwhile, CPUx gets round to updating shared_data and asking the GIC
to send an SGI to CPUy. Internally, the GIC decides that the SGI is
more important than the peripheral interrupt (which hasn't yet been
ACKed) but doesn't need to do anything to CPUy, because the IRQ line
is already raised.

CPUy then reads the ACK register on the GIC, sees the SGI value which
confirms the branch prediction and we end up with a stale shared_data
value.

This patch fixes the problem by adding an smp_rmb() to the IPI entry
code in gic_handle_irq. As it turns out, the combination of a control
dependency and an ISB instruction from the EOI in the GICv3 driver is
enough to provide the ordering we need, so we add a comment there
justifying the absence of an explicit smp_rmb().

Cc: stable@vger.kernel.org
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
2016-05-11 10:11:51 +01:00
..
alphascale_asm9260-icoll.h irqchip/mxs: Add Alphascale ASM9260 support 2015-10-14 09:37:47 +02:00
exynos-combiner.c irqdomain: Use irq_domain_get_of_node() instead of direct field access 2015-10-13 19:01:23 +02:00
irq-alpine-msi.c irqchip/irq-alpine-msi: Release the correct domain on error 2016-03-11 10:06:55 +01:00
irq-armada-370-xp.c irqchip/armada-370-xp: Allow allocation of multiple MSIs 2016-02-16 17:36:16 +00:00
irq-ath79-cpu.c irqchip/ath79-cpu: Move the CPU IRQ driver from arch/mips/ath79/ 2016-02-17 13:47:19 +00:00
irq-ath79-misc.c irqchip/ath79-misc: Move the MISC driver from arch/mips/ath79/ 2016-02-17 13:44:31 +00:00
irq-atmel-aic5.c irqchip/atmel-aic: Remove duplicate bit operation 2016-02-08 15:03:42 +01:00
irq-atmel-aic-common.c irqchip/atmel-aic: Change return type of aic_common_set_priority() 2016-02-08 15:03:42 +01:00
irq-atmel-aic-common.h irqchip/atmel-aic: Change return type of aic_common_set_priority() 2016-02-08 15:03:42 +01:00
irq-atmel-aic.c irqchip/atmel-aic: Change return type of aic_common_set_priority() 2016-02-08 15:03:42 +01:00
irq-bcm2835.c irqchip: Kill off set_irq_flags usage 2015-09-16 16:53:38 +02:00
irq-bcm2836.c irqchip/bcm2836: Drop extra memory barrier in SMP boot. 2016-02-18 01:53:10 +00:00
irq-bcm6345-l1.c irqchips/bmips: Add bcm6345-l1 interrupt controller 2016-02-08 15:03:42 +01:00
irq-bcm7038-l1.c genirq: Remove irq argument from irq flow handlers 2015-09-16 15:47:51 +02:00
irq-bcm7120-l2.c genirq: Remove irq argument from irq flow handlers 2015-09-16 15:47:51 +02:00
irq-brcmstb-l2.c genirq: Remove irq argument from irq flow handlers 2015-09-16 15:47:51 +02:00
irq-clps711x.c irqchip: Kill off set_irq_flags usage 2015-09-16 16:53:38 +02:00
irq-crossbar.c irqchip: Convert all alloc/xlate users from of_node to fwnode 2015-10-13 19:01:23 +02:00
irq-digicolor.c irqchip: Prepare for local stub header removal 2015-07-11 23:14:23 +02:00
irq-dw-apb-ictl.c genirq: Remove irq argument from irq flow handlers 2015-09-16 15:47:51 +02:00
irq-gic-common.c irqchip/gic: Make sure all interrupts are deactivated at boot 2015-11-17 14:25:58 +01:00
irq-gic-common.h irqchip/gicv3-its: Add HW revision detection and configuration 2015-09-29 10:10:53 +02:00
irq-gic-realview.c irqchip/gic/realview: Support more RealView DCC variants 2016-03-09 09:38:05 +00:00
irq-gic-v2m.c irqchip/gic: Return IRQ_SET_MASK_OK_DONE in the set_affinity method 2016-02-19 15:42:29 +00:00
irq-gic-v3-its-pci-msi.c irqchip/gic-v3-its: Add handling of PCI requester id. 2015-10-16 13:07:13 +01:00
irq-gic-v3-its-platform-msi.c irqchip/gic-v3-its: Parse new version of msi-parent property 2015-10-16 13:07:15 +01:00
irq-gic-v3-its.c irqchip/gic-v3-its: Mark its_init() and its children as __init 2016-03-09 02:44:03 +00:00
irq-gic-v3.c irqchip/gic: Ensure ordering between read of INTACK and shared data 2016-05-11 10:11:51 +01:00
irq-gic.c irqchip/gic: Ensure ordering between read of INTACK and shared data 2016-05-11 10:11:51 +01:00
irq-hip04.c irqdomain: Use irq_domain_get_of_node() instead of direct field access 2015-10-13 19:01:23 +02:00
irq-i8259.c irqchip/i8259: Convert to use irq_set_chained_handler_and_data 2015-10-01 16:32:54 +02:00
irq-imgpdc.c genirq: Remove irq argument from irq flow handlers 2015-09-16 15:47:51 +02:00
irq-imx-gpcv2.c irqchip: Convert all alloc/xlate users from of_node to fwnode 2015-10-13 19:01:23 +02:00
irq-ingenic.c irqchip: Prepare for local stub header removal 2015-07-11 23:14:23 +02:00
irq-keystone.c irqchip: Kill off set_irq_flags usage 2015-09-16 16:53:38 +02:00
irq-ls-scfg-msi.c irqchip: Add Layerscape SCFG MSI controller support 2016-05-04 09:58:04 +01:00
irq-mbigen.c irqchip/mbigen: Handle multiple device nodes in a mbigen module 2016-03-21 11:24:11 +01:00
irq-metag-ext.c genirq: Remove irq argument from irq flow handlers 2015-09-16 15:47:51 +02:00
irq-metag.c genirq: Remove irq argument from irq flow handlers 2015-09-16 15:47:51 +02:00
irq-mips-cpu.c irqchip: Prepare for local stub header removal 2015-07-11 23:14:23 +02:00
irq-mips-gic.c irqchip/mips-gic: Don't overrun pcpu_masks array 2016-04-21 21:04:29 +02:00
irq-mmp.c irqchip: Kill off set_irq_flags usage 2015-09-16 16:53:38 +02:00
irq-moxart.c irqchip: Prepare for local stub header removal 2015-07-11 23:14:23 +02:00
irq-mtk-sysirq.c irqchip: Convert all alloc/xlate users from of_node to fwnode 2015-10-13 19:01:23 +02:00
irq-mvebu-odmi.c irqchip/gic: Return IRQ_SET_MASK_OK_DONE in the set_affinity method 2016-02-19 15:42:29 +00:00
irq-mxs.c irqchip/mxs: Fix error check of of_io_request_and_map() 2016-03-10 16:03:30 +01:00
irq-nvic.c irqchip: Convert all alloc/xlate users from of_node to fwnode 2015-10-13 19:01:23 +02:00
irq-omap-intc.c irqchip/omap-intc: Add support for spurious irq handling 2016-01-06 11:35:13 +01:00
irq-or1k-pic.c irqchip: Prepare for local stub header removal 2015-07-11 23:14:23 +02:00
irq-orion.c genirq: Remove irq argument from irq flow handlers 2015-09-16 15:47:51 +02:00
irq-partition-percpu.c irqchip: Add per-cpu interrupt partitioning library 2016-05-02 13:42:51 +02:00
irq-pic32-evic.c IRQCHIP: irq-pic32-evic: Add support for PIC32 interrupt controller 2016-01-24 02:52:20 +01:00
irq-renesas-h8s.c irqchip: renesas-h8s: Replace ctrl_outw/ctrl_inw with writew/readw 2016-01-20 22:44:13 +09:00
irq-renesas-h8300h.c h8300: Rename ctlr_out/in[bwl] to raw_read/write[bwl] 2015-12-15 10:12:03 +01:00
irq-renesas-intc-irqpin.c irqchip/renesas-intc-irqpin: Improve clock error handling and reporting 2015-11-24 16:54:19 +00:00
irq-renesas-irqc.c irqchip/renesas-irqc: Move over to nested generic chip 2015-09-29 20:41:00 +02:00
irq-s3c24xx.c irqchip/s3c24xx: Mark init_eint as __maybe_unused 2016-01-26 16:00:14 +01:00
irq-sa11x0.c ARM: kill off set_irq_flags usage 2015-07-28 13:58:13 +02:00
irq-sirfsoc.c irqchip: Prepare for local stub header removal 2015-07-11 23:14:23 +02:00
irq-st.c irqchip: st: Supply new driver for STi based devices 2015-03-03 19:48:53 +00:00
irq-sun4i.c irqchip/sun4i: Fix compilation outside of arch/arm 2016-02-02 15:46:40 +01:00
irq-sunxi-nmi.c irqchip/sunxi-nmi: Fix error check of of_io_request_and_map() 2016-03-10 16:03:30 +01:00
irq-tango.c irqchip/tango: Add support for Sigma Designs SMP86xx/SMP87xx interrupt controller 2016-02-18 01:18:14 +00:00
irq-tb10x.c genirq: Remove irq argument from irq flow handlers 2015-09-16 15:47:51 +02:00
irq-tegra.c irqchip/tegra: Switch to use irq_domain_free_irqs_common 2016-03-20 20:08:28 +01:00
irq-ts4800.c irqchip/ts4800: Make ts4800_ic_ops static const 2016-02-18 02:09:18 +00:00
irq-versatile-fpga.c irqchip/versatile-fpga: Fix PCI IRQ mapping on Versatile PB 2015-12-01 22:50:16 +01:00
irq-vf610-mscm-ir.c irqchip: Convert all alloc/xlate users from of_node to fwnode 2015-10-13 19:01:23 +02:00
irq-vic.c irqchip: Kill off set_irq_flags usage 2015-09-16 16:53:38 +02:00
irq-vt8500.c irqchip: Kill off set_irq_flags usage 2015-09-16 16:53:38 +02:00
irq-xtensa-mx.c irqchip: Prepare for local stub header removal 2015-07-11 23:14:23 +02:00
irq-xtensa-pic.c irqchip: Prepare for local stub header removal 2015-07-11 23:14:23 +02:00
irq-zevio.c irqchip/zevio: Use irq_data_get_chip_type() helper 2015-12-30 18:29:02 +01:00
irqchip.c irqchip / GIC: Convert the GIC driver to ACPI probing 2015-10-01 02:18:38 +02:00
Kconfig irqchip: Add Layerscape SCFG MSI controller support 2016-05-04 09:58:04 +01:00
Makefile irqchip: Add Layerscape SCFG MSI controller support 2016-05-04 09:58:04 +01:00
spear-shirq.c irqchip: Kill off set_irq_flags usage 2015-09-16 16:53:38 +02:00