linux-kernel - Re: [PATCH 0/4] PCI: Reset exclusions

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Message-ID: <20150116002802.GE29776@google.com>
Date:	Thu, 15 Jan 2015 18:28:02 -0600
From:	Bjorn Helgaas <bhelgaas@...gle.com>
To:	Alex Williamson <alex.williamson@...hat.com>
Cc:	linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/4] PCI: Reset exclusions

On Fri, Nov 21, 2014 at 11:24:02AM -0700, Alex Williamson wrote:
> This is really 2 sets of 2 patches, but they both add bits to
> dev_flags so are included together.
> 
> This fixes two problems we've seen with resets.  The first is for
> devices that advertise a PM reset mechanism, but it doesn't appear to
> do anything.  We add a quirk and flags bit to indicate the PM reset
> mechanism isn't viable.  This happens on some AMD GPUs and causes
> vfio-pci to assume the PM reset was successful when it really did
> nothing and we should have escalated to a PCI bus reset.  Alex
> Deucher confirms that PM reset isn't used by graphics drivers.  The
> exclusion here is for users of pci_reset_function(), which mostly
> only includes pci-sysfs and drivers like legacy KVM device assignment
> and VFIO.
> 
> The second issue is a problem identified with an Atheros wifi chip
> where in performing a bus reset of the device, we not only permanently
> lose access to the device, but it introduces host stability issues if
> we try to access it.  I've been unsuccessful in finding any way to
> make the device behave or in finding anyone with access to hardware
> documentation and errata for this device, so it seems like the most
> appropriate path is to blacklist bus resets for topologies including
> this device.  The second two patches add infrastructure and quirks to
> do this.  Thanks,
> 
> Alex
> 
> ---
> 
> Alex Williamson (4):
>       PCI: quirk Atheros AR93xx to avoid bus reset
>       PCI: Allow device quirks to exclude bus reset

I applied these two (above) to for-linus for v3.19, thanks.

>       PCI: quirk AMD/ATI VGA cards to avoid PM reset
>       PCI: Allow device quirks to exclude D3->D0 PM reset
> 
> 
>  drivers/pci/pci.c    |   42 +++++++++++++++++++++++++++++++++++++-----
>  drivers/pci/quirks.c |   35 +++++++++++++++++++++++++++++++++++
>  include/linux/pci.h  |    4 ++++
>  3 files changed, 76 insertions(+), 5 deletions(-)
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