Re: [RFC v5 1/7] PCI: Ignore resource_alignment if PCI_PROBE_ONLY was set

[Yongji Xie]

On 2016/4/6 8:48, Gavin Shan wrote:
> On Tue, Apr 05, 2016 at 09:43:29PM +0800, Yongji Xie wrote:
> > The resource_alignment will releases memory
> > resources allocated by firmware so that kernel
> > can reassign new resources later on. But this
> > will cause the problem that no resources can be
> > allocated by kernel if PCI_PROBE_ONLY was set,
> > e.g. on pSeries platform because PCI_PROBE_ONLY
> > force kernel to use firmware setup and not to
> > reassign any resources.
> >
> > To solve this problem, this patch ignores
> > resource_alignment if PCI_PROBE_ONLY was set.
> >
> > Signed-off-by: Yongji Xie <xyjxie@xxxxxxxxxxxxxxxxxx>
> > ---
> > drivers/pci/pci.c |    6 ++++++
> > 1 file changed, 6 insertions(+)
> >
> > diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> > index 602eb42..1db9267 100644
> > --- a/drivers/pci/pci.c
> > +++ b/drivers/pci/pci.c
> > @@ -4607,6 +4607,12 @@ static resource_size_t pci_specified_resource_alignment(struct pci_dev *dev)
> > 	spin_lock(&resource_alignment_lock);
> > 	p = resource_alignment_param;
> > 	while (*p) {
> > +		if (pci_has_flag(PCI_PROBE_ONLY)) {
> > +			printk(KERN_ERR "PCI: Ignore resource_alignment parameter: %s with"
> > +					" PCI_PROBE_ONLY set\n", p);
> > +			*p = 0;
> > +			break;
> It seems no "*p = 0" isn't required if I don't miss anything. If the check
> on flag PCI_PROBE_ONLY is moved before the spin_lock(), it would save a bit
> CPU cycles at least. Also, the logic looks more clear.

I used "*p = 0" in case that the warning is called
in every pci_device_add().

And the warning should be called only when users
use resource_alignment parameter. So we test
while(*p) before we call the warning.

Thanks,
Yongji

> > +		}
> > 		count = 0;
> > 		if (sscanf(p, "%d%n", &align_order, &count) == 1 &&
> > 							p[count] == '@') {
> Thanks,
> Gavin
>
> > --
> > 1.7.9.5