linux-kernel - Re: [PATCH v5 1/5] iommu: Lock group->mutex in iommu_deferred

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Message-ID: <b556b673-300f-486e-8891-809519b98797@linux.intel.com>
Date: Wed, 12 Nov 2025 10:47:38 +0800
From: Baolu Lu <baolu.lu@...ux.intel.com>
To: Nicolin Chen <nicolinc@...dia.com>, joro@...tes.org, afael@...nel.org,
 bhelgaas@...gle.com, alex@...zbot.org, jgg@...dia.com, kevin.tian@...el.com
Cc: will@...nel.org, robin.murphy@....com, lenb@...nel.org,
 linux-arm-kernel@...ts.infradead.org, iommu@...ts.linux.dev,
 linux-kernel@...r.kernel.org, linux-acpi@...r.kernel.org,
 linux-pci@...r.kernel.org, kvm@...r.kernel.org, patches@...ts.linux.dev,
 pjaroszynski@...dia.com, vsethi@...dia.com, helgaas@...nel.org,
 etzhao1900@...il.com
Subject: Re: [PATCH v5 1/5] iommu: Lock group->mutex in
 iommu_deferred_attach()

On 11/11/25 13:12, Nicolin Chen wrote:
> The iommu_deferred_attach() function invokes __iommu_attach_device(), but
> doesn't hold the group->mutex like other __iommu_attach_device() callers.
> 
> Though there is no pratical bug being triggered so far, it would be better
> to apply the same locking to this __iommu_attach_device(), since the IOMMU
> drivers nowaday are more aware of the group->mutex -- some of them use the
> iommu_group_mutex_assert() function that could be potentially in the path
> of an attach_dev callback function invoked by the __iommu_attach_device().
> 
> Worth mentioning that the iommu_deferred_attach() will soon need to check
> group->resetting_domain that must be locked also.
> 
> Thus, grab the mutex to guard __iommu_attach_device() like other callers.
> 
> Reviewed-by: Jason Gunthorpe<jgg@...dia.com>
> Reviewed-by: Kevin Tian<kevin.tian@...el.com>
> Signed-off-by: Nicolin Chen<nicolinc@...dia.com>
> ---
>   drivers/iommu/iommu.c | 13 ++++++++++---
>   1 file changed, 10 insertions(+), 3 deletions(-)

Reviewed-by: Lu Baolu <baolu.lu@...ux.intel.com>