[+cc Don, Alex D, Alex W, Bryant, Bodong, Michael, kvm list]
On Wed, Sep 27, 2017 at 01:59:22PM +0100, David Woodhouse wrote:
> From: David Woodhouse <dwmw@xxxxxxxxxxxx>
>
> Allow userspace to configure SR-IOV VFs through sysfs.
>
> Currently, we need an in-kernel driver to permit this. But sometimes
> *all* we want to do is enable the VFs so that we can assign them to
> guests; we don't actually need to deal with the PF in any other way
> from the host kernel. So let's make it possible to use UIO for that.
>
> Signed-off-by: David Woodhouse <dwmw@xxxxxxxxxxxx>
> ---
> It's not entirely clear to me why we require the driver to "enable"
> SR-IOV like this anyway — were there some which needed to do something
> special and device-specific instead of just falling through to
> pci_{en,dis}able_sriov(), such that we need to effectively whitelist
> this in the driver rather than blacklisting the "problematic" ones via
> PCI quirks?
IIUC, this question is basically "why doesn't the PCI core enable IOV
automatically when it sees an IOV-capable device?"
I think one reason is that an admin might want to control the number
of VFs we enable (e.g., via 1789382a72a5 ("PCI: SRIOV control and
status via sysfs" [1]). But I guess you already know about that,
since this patch uses that sysfs path, so maybe I don't understand
your question.
[1] http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=1789382a72a5
> drivers/uio/uio_pci_generic.c | 12 ++++++++++++
> 1 file changed, 12 insertions(+)
>
> diff --git a/drivers/uio/uio_pci_generic.c b/drivers/uio/uio_pci_generic.c
> index a56fdf9..bd196f0 100644
> --- a/drivers/uio/uio_pci_generic.c
> +++ b/drivers/uio/uio_pci_generic.c
> @@ -108,15 +108,27 @@ static void remove(struct pci_dev *pdev)
> struct uio_pci_generic_dev *gdev = pci_get_drvdata(pdev);
>
> uio_unregister_device(&gdev->info);
> + pci_disable_sriov(pdev);
> pci_disable_device(pdev);
> kfree(gdev);
> }
>
> +static int sriov_configure(struct pci_dev *pdev, int num_vfs)
> +{
> + if (!num_vfs) {
> + pci_disable_sriov(pdev);
> + return 0;
> + }
> +
> + return pci_enable_sriov(pdev, num_vfs);
> +}
> +
> static struct pci_driver uio_pci_driver = {
> .name = "uio_pci_generic",
> .id_table = NULL, /* only dynamic id's */
> .probe = probe,
> .remove = remove,
> + .sriov_configure = sriov_configure,
> };
>
> module_pci_driver(uio_pci_driver);
> --
> 2.7.4
>
> --
> dwmw2
