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Message-ID: <20170414153718.GD29349@bhelgaas-glaptop.roam.corp.google.com>
Date: Fri, 14 Apr 2017 10:37:18 -0500
From: Bjorn Helgaas <helgaas@...nel.org>
To: bodong@...lanox.com
Cc: linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
saeedm@...lanox.com, Eli Cohen <eli@...lanox.com>
Subject: Re: [v3] PCI: Add an option to control probing of VFs before
enabling SR-IOV
On Thu, Apr 13, 2017 at 01:51:40AM +0300, bodong@...lanox.com wrote:
> From: Bodong Wang <bodong@...lanox.com>
>
> Sometimes it is not desirable to probe the virtual functions after
> SRIOV is enabled. This can save host side resource usage by VF
> instances which would be eventually probed to VMs.
>
> Add a new PCI sysfs interface "sriov_drivers_autoprobe" to control
> that from the PF, all current callers still retain the same
> functionality. To modify it, echo 0/n/N (disable probe) or 1/y/Y
> (enable probe) to:
>
> /sys/bus/pci/devices/<DOMAIN:BUS:DEVICE.FUNCTION>/sriov_drivers_autoprobe
>
> Note that, the choice must be made before enabling VFs. The change
> will not take effect if VFs are already enabled. Simply, one can set
> sriov_numvfs to 0, choose whether to probe or not, and then resume
> sriov_numvfs.
>
> Signed-off-by: Bodong Wang <bodong@...lanox.com>
> Signed-off-by: Eli Cohen <eli@...lanox.com>
> Reviewed-by: Gavin Shan <gwshan@...ux.vnet.ibm.com>
> Reviewed-by: Alex Williamson <alex.williamson@...hat.com>
> Reviewed-by: Bjorn Helgaas <helgaas@...nel.org>
Applied to pci/virtualization for v4.12, thanks, Bodong!
> ---
> Documentation/ABI/testing/sysfs-bus-pci | 18 ++++++++++++++++++
> Documentation/PCI/pci-iov-howto.txt | 12 ++++++++++++
> drivers/pci/iov.c | 1 +
> drivers/pci/pci-driver.c | 22 ++++++++++++++++++----
> drivers/pci/pci-sysfs.c | 28 ++++++++++++++++++++++++++++
> drivers/pci/pci.h | 1 +
> 6 files changed, 78 insertions(+), 4 deletions(-)
>
> diff --git a/Documentation/ABI/testing/sysfs-bus-pci b/Documentation/ABI/testing/sysfs-bus-pci
> index 5a1732b..0878520 100644
> --- a/Documentation/ABI/testing/sysfs-bus-pci
> +++ b/Documentation/ABI/testing/sysfs-bus-pci
> @@ -301,3 +301,21 @@ Contact: Emil Velikov <emil.l.velikov@...il.com>
> Description:
> This file contains the revision field of the the PCI device.
> The value comes from device config space. The file is read only.
> +
> +What: /sys/bus/pci/devices/.../sriov_drivers_autoprobe
> +Date: April 2017
> +Contact: Bodong Wang<bodong@...lanox.com>
> +Description:
> + This file appears when a physical PCIe device supports SR-IOV.
> + Userspace applications can read and write to this file to
> + determine and control the enablement(1/y/Y) or disablement
> + (0/n/N) of probing Virtual Functions (VFs) by a compatible
> + driver on host side. The default value is 1(enabled) which means
> + VFs will be probed and bound to a compatible driver on the host
> + side if SR-IOV is enabled. A typical use case is writing 0 to
> + this file to disable SR-IOV drivers auto probe, then admin from
> + host is able to assign the newly created VFs to virtual machines
> + directly after SR-IOV is enabled. Note that, changing this file
> + will not affect VFs which are already probed by host. In this
> + scenario, the user must first disable SR-IOV, make the change,
> + then resume SR-IOV.
> diff --git a/Documentation/PCI/pci-iov-howto.txt b/Documentation/PCI/pci-iov-howto.txt
> index 2d91ae2..b6807df 100644
> --- a/Documentation/PCI/pci-iov-howto.txt
> +++ b/Documentation/PCI/pci-iov-howto.txt
> @@ -68,6 +68,18 @@ To disable SR-IOV capability:
> echo 0 > \
> /sys/bus/pci/devices/<DOMAIN:BUS:DEVICE.FUNCTION>/sriov_numvfs
>
> +To enable auto probing VFs by a compatible driver on the host, run
> +command bellow before enabling SR-IOV capabilities. This is the
> +default behavior.
> + echo 1 > \
> + /sys/bus/pci/devices/<DOMAIN:BUS:DEVICE.FUNCTION>/sriov_drivers_autoprobe
> +
> +To disable auto probing VFs by a compatible driver on the host, run
> +command bellow before enabling SR-IOV capabilities. Updating this
> +entry will not affect VFs which are already probed.
> + echo 0 > \
> + /sys/bus/pci/devices/<DOMAIN:BUS:DEVICE.FUNCTION>/sriov_drivers_autoprobe
> +
> 3.2 Usage example
>
> Following piece of code illustrates the usage of the SR-IOV API.
> diff --git a/drivers/pci/iov.c b/drivers/pci/iov.c
> index 2479ae8..d9dc736 100644
> --- a/drivers/pci/iov.c
> +++ b/drivers/pci/iov.c
> @@ -450,6 +450,7 @@ static int sriov_init(struct pci_dev *dev, int pos)
> iov->total_VFs = total;
> iov->pgsz = pgsz;
> iov->self = dev;
> + iov->drivers_autoprobe = true;
> pci_read_config_dword(dev, pos + PCI_SRIOV_CAP, &iov->cap);
> pci_read_config_byte(dev, pos + PCI_SRIOV_FUNC_LINK, &iov->link);
> if (pci_pcie_type(dev) == PCI_EXP_TYPE_RC_END)
> diff --git a/drivers/pci/pci-driver.c b/drivers/pci/pci-driver.c
> index afa7271..f99f7fe 100644
> --- a/drivers/pci/pci-driver.c
> +++ b/drivers/pci/pci-driver.c
> @@ -394,6 +394,18 @@ void __weak pcibios_free_irq(struct pci_dev *dev)
> {
> }
>
> +#ifdef CONFIG_PCI_IOV
> +static inline bool pci_device_can_probe(struct pci_dev *pdev)
> +{
> + return (!pdev->is_virtfn || pdev->physfn->sriov->drivers_autoprobe);
> +}
> +#else
> +static inline bool pci_device_can_probe(struct pci_dev *pdev)
> +{
> + return true;
> +}
> +#endif
> +
> static int pci_device_probe(struct device *dev)
> {
> int error;
> @@ -405,10 +417,12 @@ static int pci_device_probe(struct device *dev)
> return error;
>
> pci_dev_get(pci_dev);
> - error = __pci_device_probe(drv, pci_dev);
> - if (error) {
> - pcibios_free_irq(pci_dev);
> - pci_dev_put(pci_dev);
> + if (pci_device_can_probe(pci_dev)) {
> + error = __pci_device_probe(drv, pci_dev);
> + if (error) {
> + pcibios_free_irq(pci_dev);
> + pci_dev_put(pci_dev);
> + }
> }
>
> return error;
> diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c
> index 25d010d..369c999 100644
> --- a/drivers/pci/pci-sysfs.c
> +++ b/drivers/pci/pci-sysfs.c
> @@ -526,10 +526,37 @@ static ssize_t sriov_numvfs_store(struct device *dev,
> return count;
> }
>
> +static ssize_t sriov_drivers_autoprobe_show(struct device *dev,
> + struct device_attribute *attr,
> + char *buf)
> +{
> + struct pci_dev *pdev = to_pci_dev(dev);
> +
> + return sprintf(buf, "%u\n", pdev->sriov->drivers_autoprobe);
> +}
> +
> +static ssize_t sriov_drivers_autoprobe_store(struct device *dev,
> + struct device_attribute *attr,
> + const char *buf, size_t count)
> +{
> + struct pci_dev *pdev = to_pci_dev(dev);
> + bool drivers_autoprobe;
> +
> + if (kstrtobool(buf, &drivers_autoprobe) < 0)
> + return -EINVAL;
> +
> + pdev->sriov->drivers_autoprobe = drivers_autoprobe;
> +
> + return count;
> +}
> +
> static struct device_attribute sriov_totalvfs_attr = __ATTR_RO(sriov_totalvfs);
> static struct device_attribute sriov_numvfs_attr =
> __ATTR(sriov_numvfs, (S_IRUGO|S_IWUSR|S_IWGRP),
> sriov_numvfs_show, sriov_numvfs_store);
> +static struct device_attribute sriov_drivers_autoprobe_attr =
> + __ATTR(sriov_drivers_autoprobe, (S_IRUGO|S_IWUSR|S_IWGRP),
> + sriov_drivers_autoprobe_show, sriov_drivers_autoprobe_store);
> #endif /* CONFIG_PCI_IOV */
>
> static ssize_t driver_override_store(struct device *dev,
> @@ -1549,6 +1576,7 @@ static umode_t pci_dev_hp_attrs_are_visible(struct kobject *kobj,
> static struct attribute *sriov_dev_attrs[] = {
> &sriov_totalvfs_attr.attr,
> &sriov_numvfs_attr.attr,
> + &sriov_drivers_autoprobe_attr.attr,
> NULL,
> };
>
> diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
> index 8dd38e6..3ba7d58 100644
> --- a/drivers/pci/pci.h
> +++ b/drivers/pci/pci.h
> @@ -272,6 +272,7 @@ struct pci_sriov {
> struct pci_dev *self; /* this PF */
> struct mutex lock; /* lock for setting sriov_numvfs in sysfs */
> resource_size_t barsz[PCI_SRIOV_NUM_BARS]; /* VF BAR size */
> + bool drivers_autoprobe; /* auto probing of VFs by driver */
> };
>
> #ifdef CONFIG_PCI_ATS
> --
> 1.7.1
>
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