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From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: Hans de Goede <hdegoede@redhat.com>
Cc: Mathias Nyman <mathias.nyman@intel.com>,
	Pavankumar Kondeti <pkondeti@codeaurora.org>,
	linux-usb <linux-usb@vger.kernel.org>
Subject: Re: Regression: "xhci: Fix command ring pointer corruption while aborting a command" breaks USB on Intel controllers
Date: Sun, 5 Dec 2021 13:48:18 +0100	[thread overview]
Message-ID: <Yay1EiY/F7ezPeb6@kroah.com> (raw)
In-Reply-To: <Yax2MOuKXECUxzbd@kroah.com>

On Sun, Dec 05, 2021 at 09:20:00AM +0100, Greg Kroah-Hartman wrote:
> On Sat, Dec 04, 2021 at 03:15:15PM +0100, 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):
> > 
> > https://bugzilla.redhat.com/show_bug.cgi?id=2019788
> > https://bbs.archlinux.org/viewtopic.php?pid=2006862
> > 
> > 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"):
> > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=ff0e50d3564f
> > 
> > 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 https://bugzilla.redhat.com/show_bug.cgi?id=2019788).
> > 
> > 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.
> 
> I think this is fixed by 09f736aa9547 ("xhci: Fix commad ring abort,
> write all 64 bits to CRCR register.") in linux-next and I'll be sending
> it to Linus in a few hours.

Pull request is here:
	https://lore.kernel.org/r/Yayq/Xdb/pHSS7/l@kroah.com


  reply	other threads:[~2021-12-05 12:48 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
2021-12-05  8:20   ` Greg Kroah-Hartman
2021-12-05  8:20 ` Greg Kroah-Hartman
2021-12-05 12:48   ` Greg Kroah-Hartman [this message]
2021-12-07  0:46     ` Tobias Bachmann

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