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

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Message-ID: <20231221104254.GB12714@wunner.de>
Date: Thu, 21 Dec 2023 11:42:54 +0100
From: Lukas Wunner <lukas@...ner.de>
To: Robin Murphy <robin.murphy@....com>
Cc: Ethan Zhao <haifeng.zhao@...ux.intel.com>, 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 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
at any time.

Thanks,

Lukas