linux-kernel - Re: [PATCH v5 5/5] pci: Suspend iommu function prior to resetting a device

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Message-ID: <aRwrlOfuFWa8ODQK@Asurada-Nvidia>
Date: Tue, 18 Nov 2025 00:17:24 -0800
From: Nicolin Chen <nicolinc@...dia.com>
To: "Tian, Kevin" <kevin.tian@...el.com>
CC: "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>,
	"will@...nel.org" <will@...nel.org>, "robin.murphy@....com"
	<robin.murphy@....com>, "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 v5 5/5] pci: Suspend iommu function prior to resetting a
 device

On Tue, Nov 18, 2025 at 07:53:27AM +0000, Tian, Kevin wrote:
> > From: Nicolin Chen <nicolinc@...dia.com>
> > And how do you think of the followings?
> > 
> > /*
> >  * Per PCIe r6.3, sec 10.3.1 IMPLEMENTATION NOTE, software disables ATS
> > before
> >  * initiating a reset. Though not all IOMMU drivers calls pci_enable_ats(), it
> >  * only gets invoked in IOMMU driver. And it is racy to check dev-
> > >ats_enabled
> >  * here, as a concurrent IOMMU attachment can enable ATS right after this
> > line.
> >  *
> >  * Notify the IOMMU driver to stop IOMMU translations until the reset is
> > done,
> >  * to ensure that the ATS function and its related invalidations are disabled.
> >  */
> > 
> 
> I'd remove the words between "Though not ..." and "after this line", which
> could be explained in iommu side following Bjorn's suggestion to not check
> pci_ats_supported() in pci core.

OK. Thanks!

Nicolin