linux-kernel - Re: [PATCH v3 5/5] pci: Suspend iommu function prior to resetting a device

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Message-ID: <aKgPr3mUcIsd1iuT@Asurada-Nvidia>
Date: Thu, 21 Aug 2025 23:35:27 -0700
From: Nicolin Chen <nicolinc@...dia.com>
To: Jason Gunthorpe <jgg@...dia.com>
CC: Ethan Zhao <etzhao1900@...il.com>, <robin.murphy@....com>,
	<joro@...tes.org>, <bhelgaas@...gle.com>, <will@...nel.org>,
	<robin.clark@....qualcomm.com>, <yong.wu@...iatek.com>,
	<matthias.bgg@...il.com>, <angelogioacchino.delregno@...labora.com>,
	<thierry.reding@...il.com>, <vdumpa@...dia.com>, <jonathanh@...dia.com>,
	<rafael@...nel.org>, <lenb@...nel.org>, <kevin.tian@...el.com>,
	<yi.l.liu@...el.com>, <baolu.lu@...ux.intel.com>,
	<linux-arm-kernel@...ts.infradead.org>, <iommu@...ts.linux.dev>,
	<linux-kernel@...r.kernel.org>, <linux-arm-msm@...r.kernel.org>,
	<linux-mediatek@...ts.infradead.org>, <linux-tegra@...r.kernel.org>,
	<linux-acpi@...r.kernel.org>, <linux-pci@...r.kernel.org>,
	<patches@...ts.linux.dev>, <pjaroszynski@...dia.com>, <vsethi@...dia.com>,
	<helgaas@...nel.org>
Subject: Re: [PATCH v3 5/5] pci: Suspend iommu function prior to resetting a
 device

On Thu, Aug 21, 2025 at 10:07:41AM -0300, Jason Gunthorpe wrote:
> On Tue, Aug 19, 2025 at 02:59:07PM -0700, Nicolin Chen wrote:
> >  c) multiple pci_devs with their own RIDs
> > 
> >     In this case, either FLR or IOMMU only resets the PF. That
> >     being said, VFs might be affected since PF is resetting?
> >     If there is an issue, I don't see it coming from the IOMMU-
> >     level reset..
> 
> It would still allow the ATS issue from the VF side. The VF could be
> pushing an invalidation during the PF reset that will get clobbered.
> 
> I haven't fully checked but I think Linux doesn't really (easially?)
> allow resetting a PF while a VF is present...

Hmm, what if the PF encountered some fault? Does Linux have a choice
not to reset PF?

> Arguably if the PF is reset the VFs should have their translations
> blocked too.

Yea, that sounds plausible to me. But, prior to that (an IOMMU-level
reset), should VFs be first reset at the PCI level?

Thanks
Nicolin