linux-kernel - Re: [RFC 1/2] PCI/IOV: Introduce pci_iov_sysfs

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Date:   Wed, 6 May 2020 16:10:18 -0500
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     Niklas Schnelle <schnelle@...ux.ibm.com>
Cc:     Bjorn Helgaas <bhelgaas@...gle.com>, linux-pci@...r.kernel.org,
        linux-kernel@...r.kernel.org, Pierre Morel <pmorel@...ux.ibm.com>,
        Peter Oberparleiter <oberpar@...ux.ibm.com>
Subject: Re: [RFC 1/2] PCI/IOV: Introduce pci_iov_sysfs_link() function

On Wed, May 06, 2020 at 05:41:38PM +0200, Niklas Schnelle wrote:
> currently pci_iov_add_virtfn() scans the SR-IOV bars, adds the VF to the
> bus and also creates the sysfs links between the newly added VF and its
> parent PF.

s/currently/Currently/
s/bars/BARs/

> With pdev->no_vf_scan fencing off the entire pci_iov_add_virtfn() call
> s390 as the sole pdev->no_vf_scan user thus ends up missing these sysfs
> links which are required for example by QEMU/libvirt.
> Instead of duplicating the code introduce a new pci_iov_sysfs_link()
> function for establishing sysfs links.

This looks like two paragraphs missing the blank line between.

This whole thing is not "introducing" any new functionality; it's
"refactoring" to move existing functionality around and make it
callable separately.

> Signed-off-by: Niklas Schnelle <schnelle@...ux.ibm.com>

With the fixes above and a few below:

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

> ---
>  drivers/pci/iov.c   | 36 ++++++++++++++++++++++++------------
>  include/linux/pci.h |  8 ++++++++
>  2 files changed, 32 insertions(+), 12 deletions(-)
> 
> diff --git a/drivers/pci/iov.c b/drivers/pci/iov.c
> index 4d1f392b05f9..d0ddf5f5484c 100644
> --- a/drivers/pci/iov.c
> +++ b/drivers/pci/iov.c
> @@ -113,7 +113,6 @@ resource_size_t pci_iov_resource_size(struct pci_dev *dev, int resno)
>  static void pci_read_vf_config_common(struct pci_dev *virtfn)
>  {
>  	struct pci_dev *physfn = virtfn->physfn;
> -
>  	/*
>  	 * Some config registers are the same across all associated VFs.
>  	 * Read them once from VF0 so we can skip reading them from the
> @@ -133,12 +132,34 @@ static void pci_read_vf_config_common(struct pci_dev *virtfn)
>  			     &physfn->sriov->subsystem_device);
>  }
>  
> +int pci_iov_sysfs_link(struct pci_dev *dev,
> +		struct pci_dev *virtfn, int id)
> +{
> +	int rc;
> +	char buf[VIRTFN_ID_LEN];

Swap the order so these are declared in the order they're used below.

> +	sprintf(buf, "virtfn%u", id);
> +	rc = sysfs_create_link(&dev->dev.kobj, &virtfn->dev.kobj, buf);
> +	if (rc)
> +		goto failed;
> +	rc = sysfs_create_link(&virtfn->dev.kobj, &dev->dev.kobj, "physfn");
> +	if (rc)
> +		goto failed1;
> +
> +	kobject_uevent(&virtfn->dev.kobj, KOBJ_CHANGE);
> +
> +	return 0;

Add a blank link here to separate the "success" return from the error
paths.

> +failed1:
> +	sysfs_remove_link(&dev->dev.kobj, buf);
> +failed:
> +	return rc;
> +}
> +
>  int pci_iov_add_virtfn(struct pci_dev *dev, int id)
>  {
>  	int i;
>  	int rc = -ENOMEM;
>  	u64 size;
> -	char buf[VIRTFN_ID_LEN];
>  	struct pci_dev *virtfn;
>  	struct resource *res;
>  	struct pci_sriov *iov = dev->sriov;
> @@ -182,23 +203,14 @@ int pci_iov_add_virtfn(struct pci_dev *dev, int id)
>  	}
>  
>  	pci_device_add(virtfn, virtfn->bus);
> -
> -	sprintf(buf, "virtfn%u", id);
> -	rc = sysfs_create_link(&dev->dev.kobj, &virtfn->dev.kobj, buf);
> +	rc = pci_iov_sysfs_link(dev, virtfn, id);
>  	if (rc)
>  		goto failed1;
> -	rc = sysfs_create_link(&virtfn->dev.kobj, &dev->dev.kobj, "physfn");
> -	if (rc)
> -		goto failed2;
> -
> -	kobject_uevent(&virtfn->dev.kobj, KOBJ_CHANGE);
>  
>  	pci_bus_add_device(virtfn);
>  
>  	return 0;
>  
> -failed2:
> -	sysfs_remove_link(&dev->dev.kobj, buf);
>  failed1:
>  	pci_stop_and_remove_bus_device(virtfn);
>  	pci_dev_put(dev);
> diff --git a/include/linux/pci.h b/include/linux/pci.h
> index 83ce1cdf5676..e97d27ac350a 100644
> --- a/include/linux/pci.h
> +++ b/include/linux/pci.h
> @@ -2048,6 +2048,8 @@ int pci_iov_virtfn_devfn(struct pci_dev *dev, int id);
>  
>  int pci_enable_sriov(struct pci_dev *dev, int nr_virtfn);
>  void pci_disable_sriov(struct pci_dev *dev);
> +
> +int pci_iov_sysfs_link(struct pci_dev *dev, struct pci_dev *virtfn, int id);
>  int pci_iov_add_virtfn(struct pci_dev *dev, int id);
>  void pci_iov_remove_virtfn(struct pci_dev *dev, int id);
>  int pci_num_vf(struct pci_dev *dev);
> @@ -2073,6 +2075,12 @@ static inline int pci_iov_virtfn_devfn(struct pci_dev *dev, int id)
>  }
>  static inline int pci_enable_sriov(struct pci_dev *dev, int nr_virtfn)
>  { return -ENODEV; }
> +
> +static inline int pci_iov_sysfs_link(struct pci_dev *dev,
> +		struct pci_dev *virtfn, int id)

Align the second line with the args in the first line, as the rest of
this file does.

> +{
> +	return -ENODEV;
> +}
>  static inline int pci_iov_add_virtfn(struct pci_dev *dev, int id)
>  {
>  	return -ENOSYS;
> -- 
> 2.17.1
>