linux-kernel - Re: [PATCH v7 1/5] iommu: Lock group->mutex in iommu_deferred

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Message-ID: <aScn9t5ctN7FgRKD@Asurada-Nvidia>
Date: Wed, 26 Nov 2025 08:16:54 -0800
From: Nicolin Chen <nicolinc@...dia.com>
To: "Srivastava, Dheeraj Kumar" <dhsrivas@....com>
CC: <joro@...tes.org>, <afael@...nel.org>, <bhelgaas@...gle.com>,
	<alex@...zbot.org>, <jgg@...dia.com>, <will@...nel.org>,
	<robin.murphy@....com>, <lenb@...nel.org>, <kevin.tian@...el.com>,
	<baolu.lu@...ux.intel.com>, <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 v7 1/5] iommu: Lock group->mutex in
 iommu_deferred_attach()

On Wed, Nov 26, 2025 at 06:25:34PM +0530, Srivastava, Dheeraj Kumar wrote:
> On 11/22/2025 7:27 AM, 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.
> > 
> 
> Tested the series with PCI reset on PFs and VFs, including device
> pass-through to a Linux guest. All scenarios worked as expected.
> 
> Tested-by: Dheeraj Kumar Srivastava <dheerajkumar.srivastava@....com>

Thanks for testing!

Yet, this is replying to PATCH-1. So, you might want to reply with
your "Tested-by" tag to PATCH-0 :)

Otherwise, default B4 command might miss your tag in other patches:

  ✗ [PATCH v7 1/5] iommu: Lock group->mutex in iommu_deferred_attach()
    + Tested-by: Dheeraj Kumar Srivastava <dheerajkumar.srivastava@....com> (✓ DKIM/amd.com)
  ✗ [PATCH v7 2/5] iommu: Tidy domain for iommu_setup_dma_ops()
    + Reviewed-by: Jason Gunthorpe <jgg@...dia.com> (✗ DKIM/Nvidia.com)
  ✗ [PATCH v7 3/5] iommu: Add iommu_driver_get_domain_for_dev() helper
    + Reviewed-by: Jason Gunthorpe <jgg@...dia.com> (✗ DKIM/Nvidia.com)
  ✗ [PATCH v7 4/5] iommu: Introduce pci_dev_reset_iommu_prepare/done()
    + Reviewed-by: Jason Gunthorpe <jgg@...dia.com> (✗ DKIM/Nvidia.com)
  ✗ [PATCH v7 5/5] PCI: Suspend iommu function prior to resetting a device
    + Reviewed-by: Jason Gunthorpe <jgg@...dia.com> (✗ DKIM/Nvidia.com)

Thank you
Nicolin