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SubjectRe: [v2] PCI: Add an option to control probing of VFs before enabling SR-IOV
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On 3/27/2017 10:11 AM, Bodong Wang wrote:
> On 3/22/2017 10:53 AM, bodong@mellanox.com wrote:
>> From: Bodong Wang <bodong@mellanox.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_probe_vfs" 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_probe_vfs
>>
>> 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@mellanox.com>
>> Signed-off-by: Eli Cohen <eli@mellanox.com>
>> Reviewed-by: Gavin Shan <gwshan@linux.vnet.ibm.com>
>> ---
>> Documentation/PCI/pci-iov-howto.txt | 10 ++++++++++
>> drivers/pci/iov.c | 1 +
>> drivers/pci/pci-driver.c | 22 ++++++++++++++++++----
>> drivers/pci/pci-sysfs.c | 28 ++++++++++++++++++++++++++++
>> drivers/pci/pci.h | 1 +
>> 5 files changed, 58 insertions(+), 4 deletions(-)
>>
>> diff --git a/Documentation/PCI/pci-iov-howto.txt
>> b/Documentation/PCI/pci-iov-howto.txt
>> index 2d91ae2..902a528 100644
>> --- a/Documentation/PCI/pci-iov-howto.txt
>> +++ b/Documentation/PCI/pci-iov-howto.txt
>> @@ -68,6 +68,16 @@ To disable SR-IOV capability:
>> echo 0 > \
>> /sys/bus/pci/devices/<DOMAIN:BUS:DEVICE.FUNCTION>/sriov_numvfs
>> +To enable probing VFs by a compatible driver on the host:
>> +Before enabling SR-IOV capabilities, do:
>> + echo 1 > \
>> + /sys/bus/pci/devices/<DOMAIN:BUS:DEVICE.FUNCTION>/sriov_probe_vfs
>> +
>> +To disable probing VFs by a compatible driver on the host:
>> +Before enabling SR-IOV capabilities, do:
>> + echo 0 > \
>> + /sys/bus/pci/devices/<DOMAIN:BUS:DEVICE.FUNCTION>/sriov_probe_vfs
>> +
>> 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..70691de 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->probe_vfs = 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..2a1cf84 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->probe_vfs);
>> +}
>> +#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..1d5b89d 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_probe_vfs_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->probe_vfs);
>> +}
>> +
>> +static ssize_t sriov_probe_vfs_store(struct device *dev,
>> + struct device_attribute *attr,
>> + const char *buf, size_t count)
>> +{
>> + struct pci_dev *pdev = to_pci_dev(dev);
>> + bool probe_vfs;
>> +
>> + if (kstrtobool(buf, &probe_vfs) < 0)
>> + return -EINVAL;
>> +
>> + pdev->sriov->probe_vfs = probe_vfs;
>> +
>> + 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_probe_vfs_attr =
>> + __ATTR(sriov_probe_vfs, (S_IRUGO|S_IWUSR|S_IWGRP),
>> + sriov_probe_vfs_show, sriov_probe_vfs_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_probe_vfs_attr.attr,
>> NULL,
>> };
>> diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
>> index 8dd38e6..b7d8127d 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 probe_vfs; /* control probing of VFs */
>> };
>> #ifdef CONFIG_PCI_ATS
>
> Hi Bjorn, could you please comment?
>
> Thanks.
>
Didn't see any comment on this patch. Is there any plan to pull this
patch in?

Thanks.

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