linux-kernel - Re: [PATCH 1/1] PCI: Use resource_set

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Message-ID: <6939ab12.050a0220.29891a.9a37@mx.google.com>
Date: Wed, 10 Dec 2025 18:17:01 +0100
From: Christian Marangi <ansuelsmth@...il.com>
To: Bjorn Helgaas <helgaas@...nel.org>
Cc: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>,
	Bjorn Helgaas <bhelgaas@...gle.com>, linux-pci@...r.kernel.org,
	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Subject: Re: [PATCH 1/1] PCI: Use resource_set_range() that correctly sets
 ->end

On Wed, Dec 10, 2025 at 11:13:19AM -0600, Bjorn Helgaas wrote:
> On Mon, Dec 08, 2025 at 04:56:54PM +0200, Ilpo Järvinen wrote:
> > __pci_read_base() sets resource start and end addresses when resource
> > is larger than 4G but pci_bus_addr_t or resource_size_t are not capable
> > of representing 64-bit PCI addresses. This creates a problematic
> > resource that has non-zero flags but the start and end addresses do not
> > yield to resource size of 0 but 1.
> > 
> > Replace custom resource addresses setup with resource_set_range()
> > that correctly sets end address as -1 which results in resource_size()
> > returning 0.
> > 
> > For consistency, also use resource_set_range() in the other branch that
> > does size based resource setup.
> 
> IIUC this fixes an ath11k regression (and probably others).  And
> typically when booting a 32-bit kernel with a device with a BAR larger
> than 4GB?
> 
> Christian, is there any dmesg snippet we could include here to help
> users diagnose the problem?  I guess the "can't handle BAR larger than
> 4GB" message is probably one clue.
> 
> Are you able to test this and verify that it fixes the regression you
> saw?
>

No my regression was on a different section and for AHB cards, no PCI.
(I sent a fix for my regression on the net mailing list)

Could be hard to find a device with 4+ gb of ram that is not x86 or on
an ipq SoC.

> > Fixes: 23b13bc76f35 ("PCI: Fail safely if we can't handle BARs larger than 4GB")
> > Link: https://lore.kernel.org/all/20251207215359.28895-1-ansuelsmth@gmail.com/T/#m990492684913c5a158ff0e5fc90697d8ad95351b
> > Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
> > Cc: stable@...r.kernel.org
> > Cc: Christian Marangi <ansuelsmth@...il.com>
> > ---
> >  drivers/pci/probe.c | 6 ++----
> >  1 file changed, 2 insertions(+), 4 deletions(-)
> > 
> > diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
> > index 124d2d309c58..b8294a2f11f9 100644
> > --- a/drivers/pci/probe.c
> > +++ b/drivers/pci/probe.c
> > @@ -287,8 +287,7 @@ int __pci_read_base(struct pci_dev *dev, enum pci_bar_type type,
> >  		if ((sizeof(pci_bus_addr_t) < 8 || sizeof(resource_size_t) < 8)
> >  		    && sz64 > 0x100000000ULL) {
> >  			res->flags |= IORESOURCE_UNSET | IORESOURCE_DISABLED;
> > -			res->start = 0;
> > -			res->end = 0;
> > +			resource_set_range(res, 0, 0);
> >  			pci_err(dev, "%s: can't handle BAR larger than 4GB (size %#010llx)\n",
> >  				res_name, (unsigned long long)sz64);
> >  			goto out;
> > @@ -297,8 +296,7 @@ int __pci_read_base(struct pci_dev *dev, enum pci_bar_type type,
> >  		if ((sizeof(pci_bus_addr_t) < 8) && l) {
> >  			/* Above 32-bit boundary; try to reallocate */
> >  			res->flags |= IORESOURCE_UNSET;
> > -			res->start = 0;
> > -			res->end = sz64 - 1;
> > +			resource_set_range(res, 0, sz64);
> >  			pci_info(dev, "%s: can't handle BAR above 4GB (bus address %#010llx)\n",
> >  				 res_name, (unsigned long long)l64);
> >  			goto out;
> > 
> > base-commit: 43dfc13ca972988e620a6edb72956981b75ab6b0
> > -- 
> > 2.39.5
> > 

-- 
	Ansuel