From: Alex Williamson <alex.williamson@redhat.com>
To: Lu Baolu <baolu.lu@linux.intel.com>
Cc: Joerg Roedel <joro@8bytes.org>, Kevin Tian <kevin.tian@intel.com>,
Will Deacon <will@kernel.org>,
Robin Murphy <robin.murphy@arm.com>,
iommu@lists.linux.dev, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 0/2] iommu/vt-d: Fix lockdep splat in intel_iommu_init()
Date: Tue, 18 Oct 2022 15:57:56 -0600 [thread overview]
Message-ID: <20221018155756.55095893.alex.williamson@redhat.com> (raw)
In-Reply-To: <20220927053109.4053662-1-baolu.lu@linux.intel.com>
On Tue, 27 Sep 2022 13:31:07 +0800
Lu Baolu <baolu.lu@linux.intel.com> wrote:
> 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(-)
Resolves the regression for me. Hopefully Joerg will queue this for
6.1-rc. Thanks!
Tested-by: Alex Williamson <alex.williamson@redhat.com>
next prev parent reply other threads:[~2022-10-18 21:58 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-09-27 5:31 [PATCH 0/2] iommu/vt-d: Fix lockdep splat in intel_iommu_init() Lu Baolu
2022-09-27 5:31 ` [PATCH 1/2] iommu: Add gfp parameter to iommu_alloc_resv_region Lu Baolu
2022-09-27 5:31 ` [PATCH 2/2] iommu/vt-d: Use rcu_lock in get_resv_regions Lu Baolu
2022-09-30 2:23 ` [PATCH 0/2] iommu/vt-d: Fix lockdep splat in intel_iommu_init() Baolu Lu
2022-10-18 21:57 ` Alex Williamson [this message]
2022-10-19 0:49 ` Baolu Lu
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