linux-kernel - Re: [PATCH RFC v2 0/4] Disable ATS via iommu during PCI resets

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Message-ID: <d7543795-b172-4452-8789-e1c810d8075a@gmail.com>
Date: Tue, 29 Jul 2025 14:16:43 +0800
From: Ethan Zhao <etzhao1900@...il.com>
To: Jason Gunthorpe <jgg@...dia.com>
Cc: Nicolin Chen <nicolinc@...dia.com>, joro@...tes.org, will@...nel.org,
 robin.murphy@....com, rafael@...nel.org, lenb@...nel.org,
 bhelgaas@...gle.com, iommu@...ts.linux.dev, linux-kernel@...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, baolu.lu@...ux.intel.com
Subject: Re: [PATCH RFC v2 0/4] Disable ATS via iommu during PCI resets



On 7/28/2025 12:20 AM, Jason Gunthorpe wrote:
> On Sun, Jul 27, 2025 at 08:48:26PM +0800, Ethan Zhao wrote:
> 
>> At least, we can do some attempt in DPC and Hot-plug driver, and then
>> push the hardware specification update to provide pre-reset notification for
>> DPC & hotplug. does it make sense ?
> 
> I think DPC is a different case..
More complex and practical case.
> 
> If we get a DPC we should also push the iommu into blocking, disable
> ATS and abandon any outstanding ATC invalidations as part of
> recovering from the DPC. Once everythings is cleaned up we can set the
Yup, even pure software resets, there might be ATC invalidation pending
  (in software queue or HW queue).
> iommu back up again and allow the driver to recover the device.
> 
> I think the current series is a good step along that path, but we'd
> also need to improve the drivers to handle abandonding/aborting the
> ATC invalidations.
Also aborting ATC invalidation works as per-condition for DPC or 
Hot-plug cases. agree, such improvement seems necessary.
> 
> IMHO DPC and SW initiated reset are separate projects.
Of Course, Rome wasn't built in a day; I endorse the success philosophy 
of restricting project scope. The discussion is purely focused on 
technical methodology.

Thanks,
Ethan

> 
> Jason