linux-kernel - Re: [PATCH v3] PCI: Check for PCIe downtraining conditions

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Date:   Mon, 23 Jul 2018 08:21:32 +0300
From:   Tal Gilboa <talgi@...lanox.com>
To:     "Alex G." <mr.nuke.me@...il.com>,
        Bjorn Helgaas <helgaas@...nel.org>
Cc:     bhelgaas@...gle.com, alex_gagniuc@...lteam.com,
        austin_bolen@...l.com, shyam_iyer@...l.com, keith.busch@...el.com,
        linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
        Jeff Kirsher <jeffrey.t.kirsher@...el.com>,
        Ariel Elior <ariel.elior@...ium.com>,
        Michael Chan <michael.chan@...adcom.com>,
        Ganesh Goudar <ganeshgr@...lsio.com>,
        Tariq Toukan <tariqt@...lanox.com>,
        Jakub Kicinski <jakub.kicinski@...ronome.com>,
        Dave Airlie <airlied@...il.com>,
        Alex Deucher <alexander.deucher@....com>
Subject: Re: [PATCH v3] PCI: Check for PCIe downtraining conditions

On 7/19/2018 6:49 PM, Alex G. wrote:
> 
> 
> On 07/18/2018 08:38 AM, Tal Gilboa wrote:
>> On 7/16/2018 5:17 PM, Bjorn Helgaas wrote:
>>> [+cc maintainers of drivers that already use pcie_print_link_status()
>>> and GPU folks]
> [snip]
>>>
>>>> +    /* Multi-function PCIe share the same link/status. */
>>>> +    if ((PCI_FUNC(dev->devfn) != 0) || dev->is_virtfn)
>>>> +        return;
>>>> +
>>>> +    pcie_print_link_status(dev);
>>>> +}
>>
>> Is this function called by default for every PCIe device? What about 
>> VFs? We make an exception for them on our driver since a VF doesn't 
>> have access to the needed information in order to provide a meaningful 
>> message.
> 
> I'm assuming VF means virtual function. pcie_print_link_status() doesn't 
> care if it's passed a virtual function. It will try to do its job. 
> That's why I bail out three lines above, with 'dev->is_virtfn' check.
> 
> Alex

That's the point - we don't want to call pcie_print_link_status() for 
virtual functions. We make the distinction in our driver. If you want to 
change the code to call this function by default it shouldn't affect the 
current usage.