linux-kernel - Re: [PATCH v7 5/5] PCI: Suspend iommu function prior to resetting a device

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Message-ID: <aSd2fAgUlPDKukMj@Asurada-Nvidia>
Date: Wed, 26 Nov 2025 13:51:56 -0800
From: Nicolin Chen <nicolinc@...dia.com>
To: Bjorn Helgaas <helgaas@...nel.org>
CC: <joro@...tes.org>, <rafael@...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>, <etzhao1900@...il.com>
Subject: Re: [PATCH v7 5/5] PCI: Suspend iommu function prior to resetting a
 device

On Wed, Nov 26, 2025 at 03:43:13PM -0600, Bjorn Helgaas wrote:
> On Fri, Nov 21, 2025 at 05:57:32PM -0800, Nicolin Chen wrote:
> > PCIe permits a device to ignore ATS invalidation TLPs while processing a
> > reset. This creates a problem visible to the OS where an ATS invalidation
> > command will time out: e.g. an SVA domain will have no coordination with a
> > reset event and can racily issue ATS invalidations to a resetting device.
> > 
> > The PCIe r6.0, sec 10.3.1 IMPLEMENTATION NOTE recommends SW to disable and
> > block ATS before initiating a Function Level Reset. It also mentions that
> > other reset methods could have the same vulnerability as well.
> > 
> > The IOMMU subsystem provides pci_dev_reset_iommu_prepare/done() callback
> > helpers for this matter. Use them in all the existing reset functions.
> > 
> > This will attach the device to its iommu_group->blocking_domain during the
> > device reset, so as to allow IOMMU driver to:
> >  - invoke pci_disable_ats() and pci_enable_ats(), if necessary
> >  - wait for all ATS invalidations to complete
> >  - stop issuing new ATS invalidations
> >  - fence any incoming ATS queries
> > 
> > Reviewed-by: Kevin Tian <kevin.tian@...el.com>
> > Signed-off-by: Nicolin Chen <nicolinc@...dia.com>
> 
> Acked-by: Bjorn Helgaas <bhelgaas@...gle.com>

Thanks!!