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

[ethan zhao]

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@xxxxxxxxxxxx>
> >
> > 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@xxxxxxxxxxxx>
> > Signed-off-by: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>
> > ---
> > 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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