linux-kernel - [PATCH 0/2] iommu/vt-d: Fix lockdep splat in intel_iommu

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Date:   Tue, 27 Sep 2022 13:31:07 +0800
From:   Lu Baolu <baolu.lu@...ux.intel.com>
To:     Joerg Roedel <joro@...tes.org>, Kevin Tian <kevin.tian@...el.com>,
        Will Deacon <will@...nel.org>,
        Robin Murphy <robin.murphy@....com>
Cc:     iommu@...ts.linux.dev, linux-kernel@...r.kernel.org,
        Lu Baolu <baolu.lu@...ux.intel.com>
Subject: [PATCH 0/2] iommu/vt-d: Fix lockdep splat in intel_iommu_init()

Hi folks,

As commit c919739ce472 ("iommu/vt-d: Handle race between registration
and device probe") highlights, a lockdep splat issue happens after
moving iommu probing device process into iommu_device_register().

This is due to a conflict that get_resv_regions wants hold the
dmar_global_lock, but it's also possible to be called from within a
section where intel_iommu_init() already holds the lock.

Historically, before commit 5f64ce5411b46 ("iommu/vt-d: Duplicate
iommu_resv_region objects per device list"), the rcu_lock is used in
get_resv_regions. This commit converted it to dmar_global_lock in order
to allowing sleeping in iommu_alloc_resv_region().

This aims to fix the lockdep issue by making iommu_alloc_resv_region()
available in critical section and rolling dmar_global_lock back to rcu
lock in get_resv_regions of the Intel IOMMU driver.

Best regards,
baolu

Lu Baolu (2):
  iommu: Add gfp parameter to iommu_alloc_resv_region
  iommu/vt-d: Use rcu_lock in get_resv_regions

 include/linux/iommu.h                       |  2 +-
 drivers/acpi/arm64/iort.c                   |  3 ++-
 drivers/iommu/amd/iommu.c                   |  7 ++++---
 drivers/iommu/apple-dart.c                  |  2 +-
 drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c |  2 +-
 drivers/iommu/arm/arm-smmu/arm-smmu.c       |  2 +-
 drivers/iommu/intel/iommu.c                 | 12 +++++++-----
 drivers/iommu/iommu.c                       |  7 ++++---
 drivers/iommu/mtk_iommu.c                   |  3 ++-
 drivers/iommu/virtio-iommu.c                |  9 ++++++---
 10 files changed, 29 insertions(+), 20 deletions(-)

-- 
2.34.1