Re: [PATCH 1/1] PCI: Restore assigned resources fully after release

[Ilpo Järvinen]

On Thu, 17 Apr 2025, Bjorn Helgaas wrote:

> On Thu, Apr 03, 2025 at 12:31:37PM +0300, Ilpo Järvinen wrote:
> > PCI resource fitting code in __assign_resources_sorted() runs in
> > multiple steps. A resource that was successfully assigned may have to
> > be released before the next step attempts assignment again. The
> > assign+release cycle is destructive to a start-aligned struct resource
> > (bridge window or IOV resource) because the start field is overwritten
> > with the real address when the resource got assigned.
> > 
> > Properly restore the resource after releasing it. The start, end, and
> > flags fields must be stored into the related struct pci_dev_resource in
> > order to be able to restore the resource to its original state.
> > 
> > Reported-by: Guenter Roeck <linux@xxxxxxxxxxxx>
> > Fixes: 96336ec70264 ("PCI: Perform reset_resource() and build fail list in sync")
> > Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@xxxxxxxxxxxxxxx>
> 
> Applied to pci/for-linus for v6.15, thanks!
> 
> I'd like to add the following to the commit log if it's accurate:
> 
>   + One symptom:
> 
>   +   pci 0002:00:00.0: bridge window [mem size 0x00100000]: can't assign; bogus alignment

Yes, that is a good addition.

-- 
 i.

>     Reported-by: Guenter Roeck <linux@xxxxxxxxxxxx>
>   + Closes: https://lore.kernel.org/r/01eb7d40-f5b5-4ec5-b390-a5c042c30aff@xxxxxxxxxxxx/
>   + Reported-by: Nicolas Frattaroli <nicolas.frattaroli@xxxxxxxxxxxxx>
>   + Closes: https://lore.kernel.org/r/3578030.5fSG56mABF@workhorse
> 
> Let me know if that's wrong or there are additional reports.
> 
> > ---
> >  drivers/pci/setup-bus.c | 4 ++++
> >  1 file changed, 4 insertions(+)
> > 
> > diff --git a/drivers/pci/setup-bus.c b/drivers/pci/setup-bus.c
> > index 54d6f4fa3ce1..e994c546422c 100644
> > --- a/drivers/pci/setup-bus.c
> > +++ b/drivers/pci/setup-bus.c
> > @@ -187,6 +187,9 @@ static void pdev_sort_resources(struct pci_dev *dev, struct list_head *head)
> >  			panic("%s: kzalloc() failed!\n", __func__);
> >  		tmp->res = r;
> >  		tmp->dev = dev;
> > +		tmp->start = r->start;
> > +		tmp->end = r->end;
> > +		tmp->flags = r->flags;
> >  
> >  		/* Fallback is smallest one or list is empty */
> >  		n = head;
> > @@ -545,6 +548,7 @@ static void __assign_resources_sorted(struct list_head *head,
> >  		pci_dbg(dev, "%s %pR: releasing\n", res_name, res);
> >  
> >  		release_resource(res);
> > +		restore_dev_resource(dev_res);
> >  	}
> >  	/* Restore start/end/flags from saved list */
> >  	list_for_each_entry(save_res, &save_head, list)
> > 
> > base-commit: 7d06015d936c861160803e020f68f413b5c3cd9d
> > -- 
> > 2.39.5
> > 
>