From: Thomas Gleixner <tglx@linutronix.de>
To: LKML <linux-kernel@vger.kernel.org>
Cc: x86@kernel.org, Jiang Liu <jiang.liu@linux.intel.com>,
Joerg Roedel <joro@8bytes.org>, Borislav Petkov <bp@alien8.de>
Subject: [patch 0/5] x86/iommu: Bootup stage cleanups
Date: Fri, 05 Dec 2014 08:48:28 -0000 [thread overview]
Message-ID: <20141204234737.728961990@linutronix.de> (raw)
Boris reported that the conversion to stacked irqdomains causes a
GFP_KERNEL allocation from atomic context splat.
The callchain is:
kernel_init_freeable
smp_prepare_cpus
default_setup_apic_routing
enable_IR_x2apic
irq_remapping_enable
intel_enable_irq_remapping
intel_setup_irq_remapping
irq_domain_add_hierarchy
__irq_domain_add
The reason for the splat is that smp_prepare_cpus() is pointlessly
disabling preemption and enable_IR_x2apic is calling
irq_remapping_enable with interrupts disabled.
Removing the completely useless preemption disable from
smp_prepare_cpus() is a no brainer, but resolving the interrupt
disabled issue in enable_IR_x2apic/irq_remapping_enable forced me to
look deeper into the iommu setup code.
Convoluted is probably an euphemism for that maze.
The early detection of iommus happens in mem_init() which looks for
the availability of ACPI tables describing iommus.
The actual parsing of the tables happens for AMD in
setup_irq_remapping_ops() which calls remap_ops.prepare() and for
Intel in irq_remapping_enable().
The AMD parsing allocates data structures, memory pages and the irq
domain from the prepare callback, which makes a lot of sense as this
has nothing to do with the actual enablement. That AMD code uses
GFP_KERNEL allocations inside of a preempt disabled region. That issue
is solved by removing the silly preempt_disable() from
smp_prepare_cpus().
For Intel the actual parsing and allocation is moved from the enable
to the prepare callback. That cures the reported splat and allows to
use GFP_KERNEL allocations for the iommu internal stuff as well. While
in the early bootup it does not matter much, for physical hotplug
GFP_ATOMIC allocations are not desired at all.
That solves the issue at hand, but the iommu setup stays a tangled
maze with completely non obvious setup mechanisms depending on the
options (iommu on/off - irq remapping on/off).
Thanks,
tglx
---
arch/x86/include/asm/irq_remapping.h | 2 -
arch/x86/kernel/apic/apic.c | 3 -
arch/x86/kernel/smpboot.c | 8 ----
drivers/iommu/intel_irq_remapping.c | 68 +++++++++++++++++++++++------------
drivers/iommu/irq_remapping.c | 19 +++------
kernel/irq/irqdomain.c | 21 +---------
6 files changed, 56 insertions(+), 65 deletions(-)
next reply other threads:[~2014-12-05 8:48 UTC|newest]
Thread overview: 56+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-12-05 8:48 Thomas Gleixner [this message]
2014-12-05 8:48 ` [patch 1/5] x86, smpboot: Remove pointless preempt_disable() in native_smp_prepare_cpus() Thomas Gleixner
2014-12-05 23:25 ` [tip:x86/apic] " tip-bot for Thomas Gleixner
2014-12-19 14:02 ` tip-bot for Thomas Gleixner
2014-12-05 8:48 ` [patch 2/5] iommu, x86: Restructure setup of the irq remapping feature Thomas Gleixner
2014-12-05 23:25 ` [tip:x86/apic] " tip-bot for Thomas Gleixner
2014-12-05 8:48 ` [patch 3/5] iommu/vt-d: Move iommu preparatory allocations to irq_remap_ops.prepare Thomas Gleixner
2014-12-05 23:26 ` [tip:x86/apic] " tip-bot for Thomas Gleixner
2014-12-11 7:35 ` Yinghai Lu
2014-12-11 14:33 ` Jiang Liu
2014-12-11 17:57 ` Yinghai Lu
2014-12-11 20:30 ` Thomas Gleixner
2014-12-12 2:04 ` Yinghai Lu
2015-04-27 22:46 ` Yinghai Lu
2015-04-29 8:15 ` Jiang Liu
2014-12-05 8:48 ` [patch 4/5] irqdomain: Revert gfp hackery Thomas Gleixner
2014-12-05 23:26 ` [tip:x86/apic] " tip-bot for Thomas Gleixner
2014-12-05 8:48 ` [patch 5/5] iommu/vt-d: Convert allocations to GFP_KERNEL Thomas Gleixner
2014-12-05 23:26 ` [tip:x86/apic] " tip-bot for Thomas Gleixner
2014-12-05 12:22 ` [patch 0/5] x86/iommu: Bootup stage cleanups Joerg Roedel
2015-01-07 7:31 [Patch v2 00/16] Refine IR initialization flow and fixes bugs related to X2APIC Jiang Liu
2015-01-07 7:31 ` [Patch v2 01/16] iommu, x86: Restructure setup of the irq remapping feature Jiang Liu
2015-01-15 12:58 ` [tip:x86/apic] " tip-bot for Thomas Gleixner
2015-01-07 7:31 ` [Patch v2 02/16] iommu/vt-d: Move iommu preparatory allocations to irq_remap_ops.prepare Jiang Liu
2015-01-15 12:58 ` [tip:x86/apic] " tip-bot for Thomas Gleixner
2015-01-07 7:31 ` [Patch v2 03/16] iommu/vt-d: Convert allocations to GFP_KERNEL Jiang Liu
2015-01-15 12:59 ` [tip:x86/apic] " tip-bot for Thomas Gleixner
2015-01-07 7:31 ` [Patch v2 04/16] x86/apic: Panic if kernel doesn't support x2apic but BIOS has enabled x2apic Jiang Liu
2015-01-15 12:59 ` [tip:x86/apic] x86/apic: Panic if kernel doesn' t " tip-bot for Jiang Liu
2015-01-07 7:31 ` [Patch v2 05/16] x86/apic: Kill useless variable x2apic_enabled in function enable_IR_x2apic() Jiang Liu
2015-01-15 12:59 ` [tip:x86/apic] " tip-bot for Jiang Liu
2015-01-07 7:31 ` [Patch v2 06/16] x86/apic: Correctly detect X2APIC status in function enable_IR() Jiang Liu
2015-01-15 13:00 ` [tip:x86/apic] " tip-bot for Jiang Liu
2015-01-07 7:31 ` [Patch v2 07/16] x86/apic: Refine enable_IR_x2apic() and related functions Jiang Liu
2015-01-15 9:24 ` Thomas Gleixner
2015-01-15 13:00 ` [tip:x86/apic] " tip-bot for Jiang Liu
2015-01-15 13:00 ` [tip:x86/apic] x86/apic: Handle XAPIC remap mode proper tip-bot for Jiang Liu
2015-01-07 7:31 ` [Patch v2 08/16] iommu/vt-d: Prepare for killing function irq_remapping_supported() Jiang Liu
2015-01-15 13:01 ` [tip:x86/apic] " tip-bot for Jiang Liu
2015-01-07 7:31 ` [Patch v2 09/16] iommu/vt-d: Allocate IRQ remapping data structures only for all IOMMUs Jiang Liu
2015-01-15 13:01 ` [tip:x86/apic] " tip-bot for Joerg Roedel
2015-01-07 7:31 ` [Patch v2 10/16] iommu/vt-d: Allow IR works in XAPIC mode though CPU works in X2APIC mode Jiang Liu
2015-01-15 13:01 ` [tip:x86/apic] " tip-bot for Jiang Liu
2015-01-07 7:31 ` [Patch v2 11/16] x86/apic: Only disable CPU x2apic mode when necessary Jiang Liu
2015-01-15 13:02 ` [tip:x86/apic] " tip-bot for Jiang Liu
2015-01-07 7:31 ` [Patch v2 12/16] iommu/amd: Check for irq-remap support amd_iommu_prepare() Jiang Liu
2015-01-15 13:02 ` [tip:x86/apic] " tip-bot for Joerg Roedel
2015-01-07 7:31 ` [Patch v2 13/16] iommu/irq_remapping: Kill function irq_remapping_supported() and related code Jiang Liu
2015-01-15 13:02 ` [tip:x86/apic] " tip-bot for Jiang Liu
2015-01-07 7:31 ` [Patch v2 14/16] iommu/irq_remapping: Refine function irq_remapping_prepare() for maintenance Jiang Liu
2015-01-15 13:03 ` [tip:x86/apic] " tip-bot for Jiang Liu
2015-01-07 7:31 ` [Patch v2 15/16] iommu/irq_remapping: Change variable disable_irq_remap to be static Jiang Liu
2015-01-15 13:03 ` [tip:x86/apic] " tip-bot for Jiang Liu
2015-01-07 7:31 ` [Patch v2 16/16] iommu/irq_remapping: Normailize the way to detect whether IR is enabled Jiang Liu
2015-01-15 13:03 ` [tip:x86/apic] " tip-bot for Jiang Liu
2015-01-09 12:03 ` [Patch v2 00/16] Refine IR initialization flow and fixes bugs related to X2APIC Joerg Roedel
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