linux-kernel - Re: [PATCH v2] Enable SR-IOV instantiation through /sys file

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Date:   Fri, 8 Dec 2017 15:58:02 -0700
From:   Alex Williamson <alex.williamson@...hat.com>
To:     Jeff Kirsher <jeffrey.t.kirsher@...el.com>
Cc:     Liang-Min Wang <liang-min.wang@...el.com>, kvm@...r.kernel.org,
        linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
        bhelgaas@...gle.com, alexander.h.duyck@...el.com
Subject: Re: [PATCH v2] Enable SR-IOV instantiation through /sys file

On Fri,  8 Dec 2017 13:47:58 -0800
Jeff Kirsher <jeffrey.t.kirsher@...el.com> wrote:

> From: Liang-Min Wang <liang-min.wang@...el.com>
> 
> When a SR-IOV capable device is bound with vfio-pci, the
> device loses capability of creating SR-IOV instances through /sy/bus/
> pci/devices/.../sriov_numvfs. This patch re-activates this capability
> for a PCIe device that is SR-IOV capable and is bound with vfio-pci.ko.
> This patch also disables drivers_autoprobe attribute of SR-IOV devices
> created from vfio-pci bound device by default, so user-space PF device
> can coordinate the bring-up of SR-IOV devices
> 
> Signed-off-by: Liang-Min Wang <liang-min.wang@...el.com>
> ---
>  drivers/pci/pci-driver.c    | 12 ++++++++++++
>  drivers/vfio/pci/vfio_pci.c | 22 ++++++++++++++++++++++
>  include/linux/pci.h         |  1 +
>  3 files changed, 35 insertions(+)
> 
> diff --git a/drivers/pci/pci-driver.c b/drivers/pci/pci-driver.c
> index 7f47bb7..19522fe 100644
> --- a/drivers/pci/pci-driver.c
> +++ b/drivers/pci/pci-driver.c
> @@ -1467,6 +1467,18 @@ void pci_dev_put(struct pci_dev *dev)
>  }
>  EXPORT_SYMBOL(pci_dev_put);
>  
> +/**
> + * pci_dev_sriov_autoprobe_set - set device sriov driver autoprobe
> + * @dev: device with which sriov autoprobe will be set
> + *
> + */
> +void pci_dev_sriov_autoprobe_set(struct pci_dev *dev, bool autoprobe)
> +{
> +	if (dev && dev->sriov)
> +		dev->sriov->drivers_autoprobe = autoprobe;
> +}
> +EXPORT_SYMBOL(pci_dev_sriov_autoprobe_set);

_GPL?

It'd also be best to separate the pci and vfio changes into different
patches.  Bjorn would need to at least ack this PCI interface.

> +
>  static int pci_uevent(struct device *dev, struct kobj_uevent_env *env)
>  {
>  	struct pci_dev *pdev;
> diff --git a/drivers/vfio/pci/vfio_pci.c b/drivers/vfio/pci/vfio_pci.c
> index f041b1a..004836c 100644
> --- a/drivers/vfio/pci/vfio_pci.c
> +++ b/drivers/vfio/pci/vfio_pci.c
> @@ -1213,6 +1213,8 @@ static int vfio_pci_probe(struct pci_dev *pdev, const struct pci_device_id *id)
>  		return -ENOMEM;
>  	}
>  
> +	/* disable sriov automatic driver attachment */
> +	pci_dev_sriov_autoprobe_set(pdev, false);

This looks stateful, VF autoprobe is not restored on release.  Also,
how would we know the initial state to restore it to?

>  	vdev->pdev = pdev;
>  	vdev->irq_type = VFIO_PCI_NUM_IRQS;
>  	mutex_init(&vdev->igate);
> @@ -1256,6 +1258,7 @@ static void vfio_pci_remove(struct pci_dev *pdev)
>  	if (!vdev)
>  		return;
>  
> +	pci_disable_sriov(pdev);
>  	vfio_iommu_group_put(pdev->dev.iommu_group, &pdev->dev);
>  	kfree(vdev->region);
>  	kfree(vdev);
> @@ -1303,12 +1306,31 @@ static pci_ers_result_t vfio_pci_aer_err_detected(struct pci_dev *pdev,
>  	.error_detected = vfio_pci_aer_err_detected,
>  };
>  
> +static int vfio_sriov_configure(struct pci_dev *pdev, int num_vfs)
> +{
> +	int status;
> +
> +	if (!num_vfs) {
> +		pci_disable_sriov(pdev);
> +		return 0;
> +	}
> +
> +	status = pci_enable_sriov(pdev, num_vfs);
> +	if (!status) {
> +		pr_crit("Created %d SR-IOV from a user-space driver based upon vfio-pci\n", num_vfs);
> +		add_taint(TAINT_USER, LOCKDEP_STILL_OK);
> +	}

This probably deserves more explanation, in comment and commit log.
Probably a dev_crit() is also justified, knowing the PF would be
useful.  Thanks,

Alex

> +
> +	return status;
> +}
> +
>  static struct pci_driver vfio_pci_driver = {
>  	.name		= "vfio-pci",
>  	.id_table	= NULL, /* only dynamic ids */
>  	.probe		= vfio_pci_probe,
>  	.remove		= vfio_pci_remove,
>  	.err_handler	= &vfio_err_handlers,
> +	.sriov_configure = vfio_sriov_configure,
>  };
>  
>  struct vfio_devices {
> diff --git a/include/linux/pci.h b/include/linux/pci.h
> index 0403894..e04b69d 100644
> --- a/include/linux/pci.h
> +++ b/include/linux/pci.h
> @@ -921,6 +921,7 @@ struct resource *pci_find_parent_resource(const struct pci_dev *dev,
>  struct pci_dev *pci_dev_get(struct pci_dev *dev);
>  void pci_dev_put(struct pci_dev *dev);
>  void pci_remove_bus(struct pci_bus *b);
> +void pci_dev_sriov_autoprobe_set(struct pci_dev *dev, bool autoprobe);
>  void pci_stop_and_remove_bus_device(struct pci_dev *dev);
>  void pci_stop_and_remove_bus_device_locked(struct pci_dev *dev);
>  void pci_stop_root_bus(struct pci_bus *bus);