linux-kernel - Re: [pci PATCH v6 1/5] pci: Add pci_sriov_configure_simple for PFs that don't manage VF resources

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Date:   Wed, 14 Mar 2018 08:28:18 -0700
From:   Alexander Duyck <alexander.duyck@...il.com>
To:     Christoph Hellwig <hch@....de>
Cc:     Bjorn Helgaas <bhelgaas@...gle.com>,
        "Duyck, Alexander H" <alexander.h.duyck@...el.com>,
        linux-pci@...r.kernel.org, virtio-dev@...ts.oasis-open.org,
        kvm@...r.kernel.org, Netdev <netdev@...r.kernel.org>,
        "Daly, Dan" <dan.daly@...el.com>,
        LKML <linux-kernel@...r.kernel.org>,
        linux-nvme@...ts.infradead.org,
        Keith Busch <keith.busch@...el.com>, netanel@...zon.com,
        Don Dutile <ddutile@...hat.com>,
        Maximilian Heyne <mheyne@...zon.de>,
        "Wang, Liang-min" <liang-min.wang@...el.com>,
        "Rustad, Mark D" <mark.d.rustad@...el.com>,
        David Woodhouse <dwmw2@...radead.org>, dwmw@...zon.co.uk
Subject: Re: [pci PATCH v6 1/5] pci: Add pci_sriov_configure_simple for PFs
 that don't manage VF resources

On Wed, Mar 14, 2018 at 1:54 AM, Christoph Hellwig <hch@....de> wrote:
> On Tue, Mar 13, 2018 at 02:28:49PM -0700, Alexander Duyck wrote:
>> From: Alexander Duyck <alexander.h.duyck@...el.com>
>>
>> This patch adds a common configuration function called
>> pci_sriov_configure_simple that will allow for managing VFs on devices
>> where the PF is not capable of managing VF resources.
>>
>> Signed-off-by: Alexander Duyck <alexander.h.duyck@...el.com>
>> ---
>>
>> v5: New patch replacing pci_sriov_configure_unmanaged with
>>       pci_sriov_configure_simple
>>     Dropped bits related to autoprobe changes
>> v6: Defined pci_sriov_configure_simple as NULL if IOV is disabled
>>
>>  drivers/pci/iov.c   |   32 ++++++++++++++++++++++++++++++++
>>  include/linux/pci.h |    3 +++
>>  2 files changed, 35 insertions(+)
>>
>> diff --git a/drivers/pci/iov.c b/drivers/pci/iov.c
>> index 677924ae0350..bd7021491fdb 100644
>> --- a/drivers/pci/iov.c
>> +++ b/drivers/pci/iov.c
>> @@ -807,3 +807,35 @@ int pci_sriov_get_totalvfs(struct pci_dev *dev)
>>       return dev->sriov->total_VFs;
>>  }
>>  EXPORT_SYMBOL_GPL(pci_sriov_get_totalvfs);
>> +
>> +/**
>> + * pci_sriov_configure_simple - helper to configure unmanaged SR-IOV
>> + * @dev: the PCI device
>> + * @nr_virtfn: number of virtual functions to enable, 0 to disable
>> + *
>> + * Used to provide generic enable/disable SR-IOV option for devices
>> + * that do not manage the VFs generated by their driver
>> + */
>> +int pci_sriov_configure_simple(struct pci_dev *dev, int nr_virtfn)
>> +{
>> +     int err = -EINVAL;
>
> This assignment seems like it is never used..

It applies in the case where we are setting a number of VFs when VFs
are already allocated. It was needed since the last statement ended in
an if.

>> +
>> +     might_sleep();
>> +
>> +     if (!dev->is_physfn)
>> +             return -ENODEV;
>> +
>> +     if (pci_vfs_assigned(dev)) {
>> +             pci_warn(dev,
>> +                      "Cannot modify SR-IOV while VFs are assigned\n");
>> +             err = -EPERM;
>
> Why not:
>
>         if (pci_vfs_assigned(dev)) {
>                 pci_warn(dev,
>                          "Cannot modify SR-IOV while VFs are assigned\n");
>                 return -EPERM;
>         }

Symmetry. I had this as one of 3 blocks and just did it this way to be
consistent with the next two statements. I could probably just return
from each if block if that is preferred.

> Otherwise looks good:
>
> Reviewed-by: Christoph Hellwig <hch@....de>

For v7 I can probably drop the err parameter and just return the
necessary error values directly.