linux-kernel - Re: [PATCH 2/2] iommu/vt-d: don's issue devTLB flush request when device is disconnected

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Date: Fri, 22 Dec 2023 11:20:18 +0800
From: Ethan Zhao <haifeng.zhao@...ux.intel.com>
To: Lukas Wunner <lukas@...ner.de>, Robin Murphy <robin.murphy@....com>
Cc: bhelgaas@...gle.com, baolu.lu@...ux.intel.com, dwmw2@...radead.org,
 will@...nel.org, linux-pci@...r.kernel.org, iommu@...ts.linux.dev,
 linux-kernel@...r.kernel.org, Haorong Ye <yehaorong@...edance.com>
Subject: Re: [PATCH 2/2] iommu/vt-d: don's issue devTLB flush request when
 device is disconnected


On 12/21/2023 6:42 PM, Lukas Wunner wrote:
> On Wed, Dec 13, 2023 at 11:54:05AM +0000, Robin Murphy wrote:
>> I think if we want to ensure ATCs are invalidated on hot-unplug we need an
>> additional pre-removal notifier to take care of that, and that step would
>> then want to distinguish between an orderly removal where cleaning up is
>> somewhat meaningful, and a surprise removal where it definitely isn't.
> Even if a user starts the process for orderly removal, the device may be
> surprise-removed *during* that process.  So we cannot assume that the
> device is actually accessible if orderly removal has been initiated.
> If the form factor supports surprise removal, the device may be gone

There is no hardware lock to prevent user powerring-off/removing

the supprise-removal capable device before issuing ATS invalidation

request but after checking device connection state, the no target

request still possibly be sent.


Thanks,

Ethan

> at any time.
>
> Thanks,
>
> Lukas
>