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

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Message-ID: <20250828184608.GF7333@nvidia.com>
Date: Thu, 28 Aug 2025 15:46:08 -0300
From: Jason Gunthorpe <jgg@...dia.com>
To: Nicolin Chen <nicolinc@...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 28, 2025 at 08:08:13AM -0700, Nicolin Chen wrote:
> On Thu, Aug 28, 2025 at 09:51:49AM -0300, Jason Gunthorpe wrote:
> > On Fri, Aug 22, 2025 at 11:50:58AM -0700, Nicolin Chen wrote:
> > 
> > > It feels like we need a no-fail re-attach operation, or at least an
> > > unlikely-to-fail one. I recall years ago we tried a can_attach op
> > > to test the compatibility but it didn't get merged. Maybe we'd need
> > > it so that a concurrent attach can test compatibility, allowing the
> > > re-attach in iommu_dev_reset_done() to more likely succeed.
> > 
> > This is probably the cleanest option to split these things
> 
> Yea, that could avoid failing a concurrent attach_dev during FLR
> unless the dryrun fails, helping non-SRIOV cases too.
> 
> So, next version could have some new preparatory patches:
>  - Pass in old domain to attach_dev
>  - Add a can_attach_dev op

I wouldn't make this more complicated, just focus on the signal device
case here then we move on from there

Just adding can_attach_dev is big series on its own

Jason