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From: Thorsten Leemhuis <>
To: Hans de Goede <>,
	Mathias Nyman <>,
	Pavankumar Kondeti <>,
	Greg Kroah-Hartman <>
Cc: linux-usb <>
Subject: Re: Regression: "xhci: Fix command ring pointer corruption while aborting a command" breaks USB on Intel controllers
Date: Sun, 5 Dec 2021 07:46:39 +0100	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>

Hi, this is your Linux kernel regression tracker speaking.

On 04.12.21 15:15, Hans de Goede wrote:
> Hi All,
> There are several bug reports (arch and Fedora) about USB problems
> starting with kernel 5.14.14 (5.14.13 is ok):
> And 5.16.6, which has the hub address0_mutex fixes does not
> fix these problems for some users.
> Looking at the history between those 2 commit ff0e50d3564f
> ("xhci: Fix command ring pointer corruption while aborting a command"):
> stood out to me as a possible cause of this. So I've build
> a test 5.15.6 kernel for Fedora users with that commit reverted
> and 2 users have now reported that this fixes things for them
> (see
> The reason why this stood out to me is because doing a 32 bit
> write over a possibly 64 bit databus to the xHCI controller may
> result in the hw doing a 64 bit read + modify 32 bit + 64 bit write,
> so I think that the following is happening after the commit:
> sw: read 32 bit
> hw: read 64 bit, return 32 bit
> sw: modify it
> sw: write 32 bit
> hw: read 64 bit
> hw: modify 32 bit of 64 bit wor5d
> hw: write 64 bit
> Which actually makes the chances of hitting the problem the commit
> tries to fix larger on controllers using a 64 bit data bus.
> Note this is just a theory, but it seems plausible to me.
> All problem reports are people using integrated Intel xHCI controllers
> which I believe are likely to use a 64 bit data-bus.

FWIW, the commit is known to cause problems, one of them is found here:

This commit should improve the situation (and afaics hopefully fix all
problems related to it):

Greg wants to sent it upstream today:

Guess he soon after will backport it to the stable trees as well.

HTH, Ciao, Thorsten

#regzbot ^backmonitor

  reply	other threads:[~2021-12-05  6:46 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-12-04 14:15 Hans de Goede
2021-12-05  6:46 ` Thorsten Leemhuis [this message]
2021-12-05  8:20   ` Greg Kroah-Hartman
2021-12-05  8:20 ` Greg Kroah-Hartman
2021-12-05 12:48   ` Greg Kroah-Hartman
2021-12-07  0:46     ` Tobias Bachmann

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