linux-kernel - Re: [v2] PCI: Add an option to control probing of VFs before enabling SR-IOV

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Date:   Fri, 31 Mar 2017 10:07:24 -0500
From:   Bodong Wang <bodong@...lanox.com>
To:     <bhelgaas@...gle.com>
CC:     <linux-pci@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <saeedm@...lanox.com>, Eli Cohen <eli@...lanox.com>
Subject: Re: [v2] PCI: Add an option to control probing of VFs before enabling
 SR-IOV

On 3/27/2017 10:11 AM, Bodong Wang wrote:
> On 3/22/2017 10:53 AM, 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_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@...lanox.com>
>> Signed-off-by: Eli Cohen <eli@...lanox.com>
>> Reviewed-by: Gavin Shan <gwshan@...ux.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.