linux-kernel - Re: [Xen-devel] [PATCH v5 9/9] xen/pciback: Implement PCI reset slot or bus with 'do

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Message-ID: <54857F91.3020002@citrix.com>
Date:	Mon, 8 Dec 2014 10:38:09 +0000
From:	David Vrabel <david.vrabel@...rix.com>
To:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
CC:	Alex Williamson <alex.williamson@...hat.com>,
	Sander Eikelenboom <linux@...elenboom.it>,
	<bhelgaas@...gle.com>, <linux-pci@...r.kernel.org>,
	Boris Ostrovsky <boris.ostrovsky@...cle.com>,
	<linux-kernel@...r.kernel.org>, <xen-devel@...ts.xenproject.org>
Subject: Re: [Xen-devel] [PATCH v5 9/9] xen/pciback: Implement PCI reset slot
 or bus with 'do_flr' SysFS attribute

On 05/12/14 17:22, Konrad Rzeszutek Wilk wrote:
> On Fri, Dec 05, 2014 at 10:30:01AM +0000, David Vrabel wrote:
>> On 04/12/14 15:39, Alex Williamson wrote:
>>>
>>> I don't know what workaround you're talking about.  As devices are
>>> released from the user, vfio-pci attempts to reset them.  If
>>> pci_reset_function() returns success we mark the device clean, otherwise
>>> it gets marked dirty.  Each time a device is released, if there are
>>> dirty devices we test whether we can try a bus/slot reset to clean them.
>>> In the case of assigning a GPU this typically means that the GPU or
>>> audio function come through first, there's no reset mechanism so it gets
>>> marked dirty, the next device comes through and we manage to try a bus
>>> reset.  vfio-pci does not have any device specific resets, all
>>> functionality is added to the PCI-core, thank-you-very-much.  I even
>>> posted a generic PCI quirk patch recently that marks AMD VGA PM reset as
>>> bad so that pci_reset_function() won't claim that worked.  All VGA
>>> access quirks are done in QEMU, the kernel doesn't have any business in
>>> remapping config space over MMIO regions or trapping other config space
>>> backdoors.
>>
>> Thanks for the info Alex, I hadn't got around to actually looking and
>> the vfio-pci code and was just going to what Sander said.
>>
>> We probably do need to have a more in depth look at now PCI devices and
>> handled by both the toolstack and pciback but in the short term I would
>> like a simple solution that does not extend the ABI.
> 
> Could you enumerate the 'simple solution' then please? I am having
> a frustrating time figuring out what it is that you are proposing.

I've posted it repeatedly.

David
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