Re: [PATCH] iov: initialize NumVFs register to 0 at the end of sriov_init()

[ethan zhao]

On 2015/9/16 0:10, Bjorn Helgaas wrote:
> On Fri, Aug 21, 2015 at 06:51:25PM +0900, Ethan Zhao wrote:
> > After commit 4449f079722c ("PCI: Calculate maximum number of buses
> > required for VFs"),the initial value of NumVFs register was set to
> > non-zero after sriov_init() and no VFs was enabled in device driver.
> > this changed the behaviour of kernel exported by lspci and sysfs etc.
> > so this patch initialize the NumVFs register to zero after the
> > calculation of max_VF_buses was done.
> >
> > Tested on stable 4.1 and passed building on stable 4.2-rc7
> >
> > Signed-off-by: Ethan Zhao <ethan.zhao@xxxxxxxxxx>
> > Tested-by: Sriharsha Yadagudde <sriharsha.devdas@xxxxxxxxxx>
> > ---
> >   drivers/pci/iov.c | 1 +
> >   1 file changed, 1 insertion(+)
> >
> > diff --git a/drivers/pci/iov.c b/drivers/pci/iov.c
> > index ee0ebff..6969084 100644
> > --- a/drivers/pci/iov.c
> > +++ b/drivers/pci/iov.c
> > @@ -476,6 +476,7 @@ found:
> >   	dev->is_physfn = 1;
> >   	iov->max_VF_buses = virtfn_max_buses(dev);
> >   
> > +	pci_iov_set_numvfs(dev, 0);
> I think it would be better to put this in virtfn_max_buses(), where we
> clobbered numVFs in the first place.  I'd also read the original value and
> restore it, e.g.,
>
>      pci_read_config_word(dev, iov->pos + PCI_SRIOV_NUM_VF, &numvfs);
>      for (nr_virtfn = 1; nr_virtfn <= iov->total_VFs; nr_virtfn++) {
>        ...
>      }
>      pci_iov_set_numvfs(dev, numvfs);
>      return max;
>
> I know sriov_init() sets numVFs to zero before it calls virtfn_max_buses(),
> but why rely on that extra knowledge?
 Yes, I think also virtfn_max_buses() should restore the register 
before it returns.
 Will revise it and resend.

 Thanks,
 Ethan
> >   	return 0;
> >   
> >   failed:
> > --
> > 1.8.3.1

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/