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

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Message-ID: <20251210171319.GA3530931@bhelgaas>
Date: Wed, 10 Dec 2025 11:13:19 -0600
From: Bjorn Helgaas <helgaas@...nel.org>
To: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
Cc: Bjorn Helgaas <bhelgaas@...gle.com>, linux-pci@...r.kernel.org,
	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	Christian Marangi <ansuelsmth@...il.com>
Subject: Re: [PATCH 1/1] PCI: Use resource_set_range() that correctly sets
 ->end

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?

> 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
>