From: Andi Kleen <andi@firstfloor.org>
To: Matthew Garrett <mjg@redhat.com>
Cc: Khalid Aziz <khalid.aziz@hp.com>,
linux-kernel@vger.kernel.org, bhelgaas@google.com,
linux-pci@vger.kernel.org
Subject: Re: [PATCH] Disable Bus Master on PCI device shutdown
Date: Thu, 07 Jun 2012 10:08:31 -0700 [thread overview]
Message-ID: <m2wr3jhwxc.fsf@firstfloor.org> (raw)
In-Reply-To: <20120606135009.GB1517@srcf.ucam.org> (Matthew Garrett's message of "Wed, 6 Jun 2012 14:50:09 +0100")
Matthew Garrett <mjg@redhat.com> writes:
>
> This protects against the case where a piece of hardware is continuing
> to DMA even after the driver shutdown method has been called? I'm not
> convinced this is safe. Some Broadcom parts will crash if busmastering
> is disabled while they're still performing DMA, and they'll then hang
> the bus if reenabled. There's also the risk that the hardware will start
> DMAing again if it's reenabled after being shut down. It seems like
> you're covering over the case where the driver didn't correctly quiesce
> the hardware, but you risk triggering other bugs instead.
One alternative I've been pondering some time is to use AER link reset
instead. But this is mainly on servers, a lot of clients don't have it.
-Andi
--
ak@linux.intel.com -- Speaking for myself only
prev parent reply other threads:[~2012-06-07 17:08 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-04-27 19:00 [PATCH] Disable Bus Master on PCI device shutdown Khalid Aziz
2012-05-03 23:52 ` Bjorn Helgaas
2012-05-04 17:15 ` Bjorn Helgaas
2012-06-06 13:50 ` Matthew Garrett
2012-06-06 16:17 ` Khalid Aziz
2012-06-06 16:27 ` Matthew Garrett
2012-06-06 17:32 ` Khalid Aziz
2012-06-06 17:42 ` Matthew Garrett
2012-06-06 18:07 ` Khalid Aziz
2012-06-06 19:42 ` Eric W. Biederman
2012-06-06 20:09 ` Matthew Garrett
2012-06-07 17:43 ` Khalid Aziz
2012-06-07 14:21 ` Khalid Aziz
2012-06-06 20:16 ` Myron Stowe
2012-06-06 23:03 ` Khalid Aziz
2012-06-06 23:18 ` Myron Stowe
2012-06-06 20:50 ` Alan Cox
2012-06-07 17:07 ` Andi Kleen
2012-06-07 17:13 ` Alan Cox
2012-06-07 17:36 ` Khalid Aziz
2012-06-07 17:08 ` Andi Kleen [this message]
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