Re: [PATCH v5] Fixes to Xen pciback for 3.17.

From: Sander Eikelenboom <linux@eikelenboom.it>
To: David Vrabel <david.vrabel@citrix.com>
Cc: gregkh@linuxfoundation.org, boris.ostrovsky@oracle.com,
	xen-devel@lists.xenproject.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v5] Fixes to Xen pciback for 3.17.
Date: Tue, 5 Aug 2014 11:44:33 +0200	[thread overview]
Message-ID: <1985206568.20140805114433__29883.5611822598$1407232001$gmane$org@eikelenboom.it> (raw)
In-Reply-To: <53E0A45C.4050400@citrix.com>

Tuesday, August 5, 2014, 11:31:08 AM, you wrote:

> On 05/08/14 09:44, Sander Eikelenboom wrote:
>> 
>> Monday, August 4, 2014, 8:43:18 PM, you wrote:
>> 
>>> On Fri, Aug 01, 2014 at 04:30:05PM +0100, David Vrabel wrote:
>>>> On 14/07/14 17:18, Konrad Rzeszutek Wilk wrote:
>>>>> Greg: goto GHK
>>>>>
>>>>> This is v5 version of patches to fix some issues in Xen PCIback.
>>>>
>>>> Applied to devel/for-linus-3.17.
>> 
>>> Thank you.
>>>>
>>>> I dropped the stable Cc for #2 pending a final decision on whether it
>>>> really is a stable candidate.
>> 
>>> OK.
>>>>
>>>> David
>> 
>> Hi Konrad / David,
>> 
>> This series still lacks a resolution on the sysfs /do_flr /reset,
>> as a result the pci devices are not reset after shutdown of a guest.
>> (no more pciback 0000:xx:xx.x: restoring config space at offset xxx)
>> 
>> So this series now introduces a regression to 3.16, which causes devices to malfunction 
>> after a guest reboot or after assigning the devices to another guest.

> I don't follow what you're saying.  The lack of a device reset for PCI
> devices with no FLR method isn't a regression as this has never worked.
>  Can you explain in more detail what the regression is and which patch
> caused it?

I haven't bisected it to a specific patch in this series,
but this patch series (when pulled on top of 3.16) cause the following:

- Do a system start and HVM guest start
- HVM guest with pci passthrough, devices work fine
- shutdown the HVM guest
- "pciback 0000:xx:xx.x: restoring config space at offset xxx" messages do not
  appear anymore when shutting down the HVM guest (as they do with vanilla 3.16)
- Starting the HVM guest again with the same devices passed through.
- Devices malfunction (for example a USB host controller will fail a simple 
  "lsusb"
- And this all works fine on vanilla 3.16.  

>> Apart from that .. i can't resist to remind the other issue with removing pci
>> devices passed through to HVM guests related to the signaling via xenstore,
>> described in:
>> 
>> http://lists.xen.org/archives/html/xen-devel/2014-07/msg01875.html

> I don't remember seeing you posting a patch...?

> David