linux-kernel - Re: [regression] usb and thunderbould are misbehaving or broken due to iommu/vt-d change

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Message-ID: <CAOcK=CM4Poawy2AN3f6C2ooPdoT=dg4J9Bg1Fu=gsFjvkrBpQw@mail.gmail.com>
Date: Thu, 29 Aug 2024 09:23:30 +0200
From: Markus Rathgeb <maggu2810@...il.com>
To: "Tian, Kevin" <kevin.tian@...el.com>
Cc: Linux regressions mailing list <regressions@...ts.linux.dev>, Lu Baolu <baolu.lu@...ux.intel.com>, 
	Will Deacon <will@...nel.org>, David Woodhouse <dwmw2@...radead.org>, Joerg Roedel <joro@...tes.org>, 
	"iommu@...ts.linux.dev" <iommu@...ts.linux.dev>, LKML <linux-kernel@...r.kernel.org>, 
	Jacob Pan <jacob.jun.pan@...ux.intel.com>, Adam Williamson <awilliam@...hat.com>
Subject: Re: [regression] usb and thunderbould are misbehaving or broken due
 to iommu/vt-d change

While reading the diff of f90584f4beb84211c4d21b319cc13f391fe9f3c2 I
wonder if the following change is correct.

It is about iommu.c and the change to domain_context_clear_one function.

Previously you first store the domain_id to did_old and then you call
context_clear_entry.
After that you use iommu->flush.flush_context and provide the did_old,
so the value before clearing the entry.

Now, you call context_clear_entry and after that you call
intel_context_flush_present that contains the remaining part.
In intel_context_flush_present the domain_id will betaken (AFTER it
has been cleared) and call flush_context with it.

Is this done by intention or changed behaviour?