Re: [Xen-devel] [PATCH V3 2/2] Xen/PCIback: Implement PCI flr/slot/bus reset with 'reset' SysFS attribute

George Dunlap
2018-09-18T09:32:17Z

> On Sep 18, 2018, at 8:15 AM, Pasi Kärkkäinen <pasik@iki.fi> wrote:
>
> Hi,
>
> On Mon, Sep 17, 2018 at 02:06:02PM -0400, Boris Ostrovsky wrote:
>> On 9/16/18 7:43 AM, Pasi Kärkkäinen wrote:
>>> Hi,
>>>
>>> On Mon, Dec 18, 2017 at 12:32:11PM -0500, Boris Ostrovsky wrote:
>>>> On 12/18/2017 02:36 AM, Jan Beulich wrote:
>>>>>>>> On 15.12.17 at 20:52, <Govinda.Tatti@Oracle.COM> wrote:
>>>>>>>>> +static int pcistub_device_reset(struct pci_dev *dev)
>>>>>>>>> +{
>>>>>>>>> + struct xen_pcibk_dev_data *dev_data;
>>>>>>>>> + bool slot = false, bus = false;
>>>>>>>>> + struct pcistub_args arg = {};
>>>>>>>>> +
>>>>>>>>> + if (!dev)
>>>>>>>>> + return -EINVAL;
>>>>>>>>> +
>>>>>>>>> + dev_dbg(&dev->dev, "[%s]\n", __func__);
>>>>>>>>> +
>>>>>>>>> + /* First check and try FLR */
>>>>>>>>> + if (pcie_has_flr(dev)) {
>>>>>>>>> + dev_dbg(&dev->dev, "resetting %s device using FLR\n",
>>>>>>>>> + pci_name(dev));
>>>>>>>>> + pcie_flr(dev);
>>>>>>>> The lack of error check here puzzled me, but I see the function
>>>>>>>> indeed returns void right now. I think the prereq patch should
>>>>>>>> change this along with exporting the function - you really don't
>>>>>>>> want the device to be handed to a guest when the FLR timed
>>>>>>>> out.
>>>>>>> We will change pcie_flr() to return error code. I will make this change
>>>>>>> in the next version of this patch.
>>>>>> I exchanged some emails with Bjorn/Christoph and it looks like Christoph
>>>>>> as some planto restructure pcie flr specific functions but I don't know
>>>>>> the exact time-frame. For now,I am planning to use existing pcie_flr()
>>>>>> after checking FLR capability. We will switchto revised pcie_flr() once
>>>>>> it is available.
>>>>>>
>>>>>> I hope you are fine with this approach. Please let me know. Thanks.
>>>>> I've seen that other discussion. I don't think the change here
>>>>> should be done prior to the error reporting being put in place,
>>>>> for security reasons. But in the end it'll be Konrad as the
>>>>> maintainer to judge.
>>>>>
>>>>> Or wait, looks like there's some confusion in ./MAINTAINERS:
>>>>> Konrad is listed as maintainer for "XEN PCI SUBSYSTEM", but the
>>>>> list of files doesn't include pciback. So it would instead be Boris
>>>>> or Jürgen to give you a final word.
>>>>
>>>> This is now 4.16 material so we can at least wait until closer to
>>>> opening of the merge window when we may have the PCI updates. (And I
>>>> just noticed that you responded to Christoph.)
>>>>
>>>> Besides, we don't want to make kernel changes until the interface is
>>>> settled (i.e the toolstack changes are accepted).
>>>>
>>> It seems Govinda's email address is giving an error, so I assume someone else needs to pick up this pciback 'reset' feature.
>>> Is it likely someone else from Oracle can/will pick up and refresh this patch, with the review comments addressed?
>>
>>
>> Govinda is no longer at Oracle.
>>
>
> Yep, thought so. Removed from CC list.
>
>
>> What about the toolstack changes? Have they been accepted? I vaguely
>> recall there was a discussion about those changes but don't remember how
>> it ended.
>>
>
> I don't think toolstack/libxl patch has been applied yet either.
>
>
> "[PATCH V1 0/1] Xen/Tools: PCI reset using 'reset' SysFS attribute":
> https://lists.xen.org/archives/html/xen-devel/2017-12/msg00664.html
>
> "[PATCH V1 1/1] Xen/libxl: Perform PCI reset using 'reset' SysFS attribute":
> https://lists.xen.org/archives/html/xen-devel/2017-12/msg00663.html
>
> George asked for some clarifications:
> https://lists.xen.org/archives/html/xen-devel/2017-12/msg01044.html
> https://lists.xen.org/archives/html/xen-devel/2017-12/msg01116.html

Right, the description of the patch didn’t actually tell you what was going on. It should have said something like, “xl currently attempts to reset a device using X; but that’s never been implemented in Linux. Instead, use Y, which [is better for whatever reason]”.

-George