netdev - Re: [PATCH mlx5-next 1/7] PCI/IOV: Provide internal VF index

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Date:   Wed, 22 Sep 2021 16:59:30 -0500
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     Leon Romanovsky <leon@...nel.org>
Cc:     Doug Ledford <dledford@...hat.com>,
        Jason Gunthorpe <jgg@...dia.com>,
        Alex Williamson <alex.williamson@...hat.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org,
        linux-rdma@...r.kernel.org, netdev@...r.kernel.org,
        Saeed Mahameed <saeedm@...dia.com>,
        Yishai Hadas <yishaih@...dia.com>
Subject: Re: [PATCH mlx5-next 1/7] PCI/IOV: Provide internal VF index

On Wed, Sep 22, 2021 at 01:38:50PM +0300, Leon Romanovsky wrote:
> From: Jason Gunthorpe <jgg@...dia.com>
> 
> The PCI core uses the VF index internally, often called the vf_id,
> during the setup of the VF, eg pci_iov_add_virtfn().
> 
> This index is needed for device drivers that implement live migration
> for their internal operations that configure/control their VFs.
>
> Specifically, mlx5_vfio_pci driver that is introduced in coming patches
> from this series needs it and not the bus/device/function which is
> exposed today.
> 
> Add pci_iov_vf_id() which computes the vf_id by reversing the math that
> was used to create the bus/device/function.
> 
> Signed-off-by: Yishai Hadas <yishaih@...dia.com>
> Signed-off-by: Jason Gunthorpe <jgg@...dia.com>
> Signed-off-by: Leon Romanovsky <leonro@...dia.com>

Acked-by: Bjorn Helgaas <bhelgaas@...gle.com>

mlx5_core_sriov_set_msix_vec_count() looks like it does basically the
same thing as pci_iov_vf_id() by iterating through VFs until it finds
one with a matching devfn (although it *doesn't* check for a matching
bus number, which seems like a bug).

Maybe that should use pci_iov_vf_id()?

> ---
>  drivers/pci/iov.c   | 14 ++++++++++++++
>  include/linux/pci.h |  7 ++++++-
>  2 files changed, 20 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/pci/iov.c b/drivers/pci/iov.c
> index dafdc652fcd0..e7751fa3fe0b 100644
> --- a/drivers/pci/iov.c
> +++ b/drivers/pci/iov.c
> @@ -33,6 +33,20 @@ int pci_iov_virtfn_devfn(struct pci_dev *dev, int vf_id)
>  }
>  EXPORT_SYMBOL_GPL(pci_iov_virtfn_devfn);
>  
> +int pci_iov_vf_id(struct pci_dev *dev)
> +{
> +	struct pci_dev *pf;
> +
> +	if (!dev->is_virtfn)
> +		return -EINVAL;
> +
> +	pf = pci_physfn(dev);
> +	return (((dev->bus->number << 8) + dev->devfn) -
> +		((pf->bus->number << 8) + pf->devfn + pf->sriov->offset)) /
> +	       pf->sriov->stride;
> +}
> +EXPORT_SYMBOL_GPL(pci_iov_vf_id);
> +
>  /*
>   * Per SR-IOV spec sec 3.3.10 and 3.3.11, First VF Offset and VF Stride may
>   * change when NumVFs changes.
> diff --git a/include/linux/pci.h b/include/linux/pci.h
> index cd8aa6fce204..4d6c73506e18 100644
> --- a/include/linux/pci.h
> +++ b/include/linux/pci.h
> @@ -2153,7 +2153,7 @@ void __iomem *pci_ioremap_wc_bar(struct pci_dev *pdev, int bar);
>  #ifdef CONFIG_PCI_IOV
>  int pci_iov_virtfn_bus(struct pci_dev *dev, int id);
>  int pci_iov_virtfn_devfn(struct pci_dev *dev, int id);
> -
> +int pci_iov_vf_id(struct pci_dev *dev);
>  int pci_enable_sriov(struct pci_dev *dev, int nr_virtfn);
>  void pci_disable_sriov(struct pci_dev *dev);
>  
> @@ -2181,6 +2181,11 @@ static inline int pci_iov_virtfn_devfn(struct pci_dev *dev, int id)
>  {
>  	return -ENOSYS;
>  }
> +static inline int pci_iov_vf_id(struct pci_dev *dev)
> +{
> +	return -ENOSYS;
> +}
> +

Drop the blank line to match the surrounding stubs.

>  static inline int pci_enable_sriov(struct pci_dev *dev, int nr_virtfn)
>  { return -ENODEV; }