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SubjectRe: [PATCH v2 5/7] PCI: Wait 1 second between disabling VFs and clearing NumVFs
Wei,

On 2015/10/30 13:14, Wei Yang wrote:
> On Thu, Oct 29, 2015 at 05:23:22PM -0500, Bjorn Helgaas wrote:
>> From: Alexander Duyck <aduyck@mirantis.com>
>>
>> Per sec 3.3.3.1 of the SR-IOV spec, r1.1, we must allow 1.0s after clearing
>> VF Enable before reading any field in the SR-IOV Extended Capability.
>>
>> Wait 1 second before calling pci_iov_set_numvfs(), which reads
>> PCI_SRIOV_VF_OFFSET and PCI_SRIOV_VF_STRIDE after it sets PCI_SRIOV_NUM_VF.
>>
>> [bhelgaas: split to separate patch for reviewability, add spec reference]
>> Signed-off-by: Alexander Duyck <aduyck@mirantis.com>
>> Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
>> ---
>> drivers/pci/iov.c | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/pci/iov.c b/drivers/pci/iov.c
>> index fada98d..24428d5 100644
>> --- a/drivers/pci/iov.c
>> +++ b/drivers/pci/iov.c
>> @@ -339,13 +339,13 @@ failed:
>> iov->ctrl &= ~(PCI_SRIOV_CTRL_VFE | PCI_SRIOV_CTRL_MSE);
>> pci_cfg_access_lock(dev);
>> pci_write_config_word(dev, iov->pos + PCI_SRIOV_CTRL, iov->ctrl);
>> - pci_iov_set_numvfs(dev, 0);
>> ssleep(1);
>> pci_cfg_access_unlock(dev);
>>
>> if (iov->link != dev->devfn)
>> sysfs_remove_link(&dev->dev.kobj, "dep_link");
>>
>> + pci_iov_set_numvfs(dev, 0);
> One small question, any specific reason put it here instead of just after
> sleep()?
Agree, pci_iov_set_numvfs(dev, 0) should be put before
pci_cfg_access_unlock(dev) to avoid race, because "NumVFs may only be
written while VF Enable is Clear"

Thanks,
Ethan
>> return rc;
>> }
>>



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