linux-kernel - RE: [PATCH v6 5/5] PCI: Suspend iommu function prior to resetting a device

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Message-ID: <BN9PR11MB527606B1150A36D5E3F6E03D8CD5A@BN9PR11MB5276.namprd11.prod.outlook.com>
Date: Fri, 21 Nov 2025 07:59:36 +0000
From: "Tian, Kevin" <kevin.tian@...el.com>
To: Nicolin Chen <nicolinc@...dia.com>, "robin.murphy@....com"
	<robin.murphy@....com>, "joro@...tes.org" <joro@...tes.org>,
	"afael@...nel.org" <afael@...nel.org>, "bhelgaas@...gle.com"
	<bhelgaas@...gle.com>, "alex@...zbot.org" <alex@...zbot.org>,
	"jgg@...dia.com" <jgg@...dia.com>
CC: "will@...nel.org" <will@...nel.org>, "lenb@...nel.org" <lenb@...nel.org>,
	"baolu.lu@...ux.intel.com" <baolu.lu@...ux.intel.com>,
	"linux-arm-kernel@...ts.infradead.org"
	<linux-arm-kernel@...ts.infradead.org>, "iommu@...ts.linux.dev"
	<iommu@...ts.linux.dev>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>, "linux-acpi@...r.kernel.org"
	<linux-acpi@...r.kernel.org>, "linux-pci@...r.kernel.org"
	<linux-pci@...r.kernel.org>, "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
	"patches@...ts.linux.dev" <patches@...ts.linux.dev>, "Jaroszynski, Piotr"
	<pjaroszynski@...dia.com>, "Sethi, Vikram" <vsethi@...dia.com>,
	"helgaas@...nel.org" <helgaas@...nel.org>, "etzhao1900@...il.com"
	<etzhao1900@...il.com>
Subject: RE: [PATCH v6 5/5] PCI: Suspend iommu function prior to resetting a
 device

> From: Nicolin Chen <nicolinc@...dia.com>
> Sent: Wednesday, November 19, 2025 8:52 AM
> 
> 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
> 
> Signed-off-by: Nicolin Chen <nicolinc@...dia.com>

Reviewed-by: Kevin Tian <kevin.tian@...el.com>