Re: [PATCH V7 8/9] PCI/IOV: Add 10-Bit Tag sysfs files for VF devices

[Bjorn Helgaas <helgaas@kernel.org>]

On Wed, Aug 04, 2021 at 09:47:07PM +0800, Dongdong Liu wrote:
> PCIe spec 5.0 r1.0 section 2.2.6.2 says that if an Endpoint supports
> sending Requests to other Endpoints (as opposed to host memory), the
> Endpoint must not send 10-Bit Tag Requests to another given Endpoint
> unless an implementation-specific mechanism determines that the
> Endpoint supports 10-Bit Tag Completer capability.
> Add sriov_vf_10bit_tag file to query the status of VF 10-Bit Tag
> Requester Enable. Add sriov_vf_10bit_tag_ctl file to disable the VF
> 10-Bit Tag Requester. The typical use case is for p2pdma when the peer
> device does not support 10-BIT Tag Completer.

Fix the usual spec quoting issue.  Or maybe this is not actually
quoted but is missing blank lines between paragraphs.

s/10-BIT/10-Bit/

> Signed-off-by: Dongdong Liu <liudongdong3@huawei.com>
> ---
>  Documentation/ABI/testing/sysfs-bus-pci | 20 +++++++++++++
>  drivers/pci/iov.c                       | 50 +++++++++++++++++++++++++++++++++
>  2 files changed, 70 insertions(+)
> 
> diff --git a/Documentation/ABI/testing/sysfs-bus-pci b/Documentation/ABI/testing/sysfs-bus-pci
> index 0e0c97d..8fdbfae 100644
> --- a/Documentation/ABI/testing/sysfs-bus-pci
> +++ b/Documentation/ABI/testing/sysfs-bus-pci
> @@ -421,3 +421,23 @@ Description:
>  		to disable 10-Bit Tag Requester when the driver does not bind
>  		the deivce. The typical use case is for p2pdma when the peer
>  		device does not support 10-BIT Tag Completer.
> +
> +What:		/sys/bus/pci/devices/.../sriov_vf_10bit_tag
> +Date:		August 2021
> +Contact:	Dongdong Liu <liudongdong3@huawei.com>
> +Description:
> +		This file is associated with a SR-IOV physical function (PF).
> +		It is visible when the device has VF 10-Bit Tag Requester
> +		Supported. It contains the status of VF 10-Bit Tag Requester
> +		Enable. The file is only readable.

s/only readable/read-only/

> +What:		/sys/bus/pci/devices/.../sriov_vf_10bit_tag_ctl

Why does this file have "_ctl" on the end when the one in patch 7/9
does not?

> +Date:		August 2021
> +Contact:	Dongdong Liu <liudongdong3@huawei.com>
> +Description:
> +		This file is associated with a SR-IOV virtual function (VF).
> +		It is visible when the device has VF 10-Bit Tag Requester
> +		Supported. It only allows to write 0 to disable VF 10-Bit
> +		Tag Requester. The file is only writeable when the vf driver
> +		does not bind to a dirver. The typical use case is for p2pdma
> +		when the peer device does not support 10-BIT Tag Completer.

s/vf/VF/
s/dirver/driver/
s/10-BIT/10-Bit/

"when the vr driver does not bind to a driver"?  Not quite right.
Must be a "device" in there somewhere.

So IIUC this file is associated with a VF, but the bit it writes is
actually in the *PF*?  So writing 0 to any VF's file disables 10-bit
tags for *all* VFs?  That's worth mentioning here.

> diff --git a/drivers/pci/iov.c b/drivers/pci/iov.c
> index 0d0bed1..04c1298 100644
> --- a/drivers/pci/iov.c
> +++ b/drivers/pci/iov.c
> @@ -220,10 +220,38 @@ static ssize_t sriov_vf_msix_count_store(struct device *dev,
>  static DEVICE_ATTR_WO(sriov_vf_msix_count);
>  #endif
>  
> +static ssize_t sriov_vf_10bit_tag_ctl_store(struct device *dev,
> +					    struct device_attribute *attr,
> +					    const char *buf, size_t count)
> +{
> +	struct pci_dev *vf_dev = to_pci_dev(dev);
> +	struct pci_dev *pdev = pci_physfn(vf_dev);
> +	struct pci_sriov *iov;
> +	bool enable;
> +
> +	if (kstrtobool(buf, &enable) < 0)
> +		return -EINVAL;
> +
> +	if (enable != false)
> +		return -EINVAL;

Is this "if (enable)" again?

> +	if (vf_dev->driver)
> +		return -EBUSY;
> +
> +	iov = pdev->sriov;
> +	iov->ctrl &= ~PCI_SRIOV_CTRL_VF_10BIT_TAG_REQ_EN;
> +	pci_write_config_word(pdev, iov->pos + PCI_SRIOV_CTRL, iov->ctrl);
> +	pci_info(pdev, "disabled SRIOV 10-Bit Tag Requester\n");

s/SRIOV/SR-IOV/ to match spec and other usages.

> +
> +	return count;
> +}
> +static DEVICE_ATTR_WO(sriov_vf_10bit_tag_ctl);
> +
>  static struct attribute *sriov_vf_dev_attrs[] = {
>  #ifdef CONFIG_PCI_MSI
>  	&dev_attr_sriov_vf_msix_count.attr,
>  #endif
> +	&dev_attr_sriov_vf_10bit_tag_ctl.attr,
>  	NULL,
>  };
>  
> @@ -236,6 +264,11 @@ static umode_t sriov_vf_attrs_are_visible(struct kobject *kobj,
>  	if (!pdev->is_virtfn)
>  		return 0;
>  
> +	pdev = pci_physfn(pdev);
> +	if ((a == &dev_attr_sriov_vf_10bit_tag_ctl.attr) &&
> +	     !(pdev->sriov->cap & PCI_SRIOV_CAP_VF_10BIT_TAG_REQ))
> +		return 0;
> +
>  	return a->mode;
>  }
>  
> @@ -487,12 +520,23 @@ static ssize_t sriov_drivers_autoprobe_store(struct device *dev,
>  	return count;
>  }
>  
> +static ssize_t sriov_vf_10bit_tag_show(struct device *dev,
> +				       struct device_attribute *attr,
> +				       char *buf)
> +{
> +	struct pci_dev *pdev = to_pci_dev(dev);
> +
> +	return sysfs_emit(buf, "%u\n",
> +		!!(pdev->sriov->ctrl & PCI_SRIOV_CTRL_VF_10BIT_TAG_REQ_EN));
> +}
> +
>  static DEVICE_ATTR_RO(sriov_totalvfs);
>  static DEVICE_ATTR_RW(sriov_numvfs);
>  static DEVICE_ATTR_RO(sriov_offset);
>  static DEVICE_ATTR_RO(sriov_stride);
>  static DEVICE_ATTR_RO(sriov_vf_device);
>  static DEVICE_ATTR_RW(sriov_drivers_autoprobe);
> +static DEVICE_ATTR_RO(sriov_vf_10bit_tag);
>  
>  static struct attribute *sriov_pf_dev_attrs[] = {
>  	&dev_attr_sriov_totalvfs.attr,
> @@ -501,6 +545,7 @@ static struct attribute *sriov_pf_dev_attrs[] = {
>  	&dev_attr_sriov_stride.attr,
>  	&dev_attr_sriov_vf_device.attr,
>  	&dev_attr_sriov_drivers_autoprobe.attr,
> +	&dev_attr_sriov_vf_10bit_tag.attr,
>  #ifdef CONFIG_PCI_MSI
>  	&dev_attr_sriov_vf_total_msix.attr,
>  #endif
> @@ -511,10 +556,15 @@ static umode_t sriov_pf_attrs_are_visible(struct kobject *kobj,
>  					  struct attribute *a, int n)
>  {
>  	struct device *dev = kobj_to_dev(kobj);
> +	struct pci_dev *pdev = to_pci_dev(dev);
>  
>  	if (!dev_is_pf(dev))
>  		return 0;
>  
> +	if ((a == &dev_attr_sriov_vf_10bit_tag.attr) &&
> +	     !(pdev->sriov->cap & PCI_SRIOV_CAP_VF_10BIT_TAG_REQ))
> +		return 0;
> +
>  	return a->mode;
>  }
>  
> -- 
> 2.7.4
>