linux-kernel - Re: [PATCH 8/9] vfio/pci: use x86 naming instead of igd

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Message-ID: <9fc2b752-88a3-0607-00fc-cb7414dcd5f6@linux.ibm.com>
Date:   Thu, 11 Feb 2021 11:29:37 -0500
From:   Matthew Rosato <mjrosato@...ux.ibm.com>
To:     Max Gurtovoy <mgurtovoy@...dia.com>,
        Jason Gunthorpe <jgg@...dia.com>,
        Cornelia Huck <cohuck@...hat.com>
Cc:     Alex Williamson <alex.williamson@...hat.com>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org, liranl@...dia.com, oren@...dia.com,
        tzahio@...dia.com, leonro@...dia.com, yarong@...dia.com,
        aviadye@...dia.com, shahafs@...dia.com, artemp@...dia.com,
        kwankhede@...dia.com, ACurrid@...dia.com, gmataev@...dia.com,
        cjia@...dia.com, yishaih@...dia.com, aik@...abs.ru
Subject: Re: [PATCH 8/9] vfio/pci: use x86 naming instead of igd

On 2/11/21 10:47 AM, Max Gurtovoy wrote:
> 
> On 2/2/2021 7:10 PM, Jason Gunthorpe wrote:
>> On Tue, Feb 02, 2021 at 05:06:59PM +0100, Cornelia Huck wrote:
>>
>>> On the other side, we have the zdev support, which both requires s390
>>> and applies to any pci device on s390.
>> Is there a reason why CONFIG_VFIO_PCI_ZDEV exists? Why not just always
>> return the s390 specific data in VFIO_DEVICE_GET_INFO if running on
>> s390?
>>
>> It would be like returning data from ACPI on other platforms.
> 
> Agree.
> 
> all agree that I remove it ?

I did some archives digging on the discussions around 
CONFIG_VFIO_PCI_ZDEV and whether we should/should not have a Kconfig 
switch around this; it was something that was carried over various 
attempts to get the zdev support upstream, but I can't really find (or 
think of) a compelling reason that a Kconfig switch must be kept for it. 
  The bottom line is if you're on s390, you really want zdev support.

So: I don't have an objection so long as the net result is that 
vfio_pci_zdev.o is always built in to vfio-pci(-core) for s390.

> 
> we already have a check in the code:
> 
> if (ret && ret != -ENODEV) {
>                                  pci_warn(vdev->vpdev.pdev, "Failed to 
> setup zPCI info capabilities\n");
>                                  return ret;
> }
> 
> so in case its not zdev we should get -ENODEV and continue in the good 
> flow.
> 
>>
>> It really seems like part of vfio-pci-core
>>
>> Jason