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

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Message-ID: <20250417163904.GA114476@bhelgaas>
Date: Thu, 17 Apr 2025 11:39:04 -0500
From: Bjorn Helgaas <helgaas@...nel.org>
To: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
Cc: Guenter Roeck <linux@...ck-us.net>, Bjorn Helgaas <bhelgaas@...gle.com>,
	linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
	Igor Mammedov <imammedo@...hat.com>,
	Mika Westerberg <mika.westerberg@...ux.intel.com>,
	Michał Winiarski <michal.winiarski@...el.com>
Subject: Re: [PATCH 1/1] PCI: Restore assigned resources fully after release

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@...ck-us.net>
> Fixes: 96336ec70264 ("PCI: Perform reset_resource() and build fail list in sync")
> Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>

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

    Reported-by: Guenter Roeck <linux@...ck-us.net>
  + Closes: https://lore.kernel.org/r/01eb7d40-f5b5-4ec5-b390-a5c042c30aff@roeck-us.net/
  + Reported-by: Nicolas Frattaroli <nicolas.frattaroli@...labora.com>
  + 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
>