linux-kernel - Re: [PATCH] PCI: decline to resize resources if boot config must be preserved

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Message-ID: <20210112224919.GA1859692@bjorn-Precision-5520>
Date:   Tue, 12 Jan 2021 16:49:19 -0600
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     Ard Biesheuvel <ardb@...nel.org>
Cc:     linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org,
        bhelgaas@...gle.com, lorenzo.pieralisi@....com,
        benh@...nel.crashing.org
Subject: Re: [PATCH] PCI: decline to resize resources if boot config must be
 preserved

On Sat, Jan 09, 2021 at 10:53:53AM +0100, Ard Biesheuvel wrote:
> The _DSM #5 method in the ACPI host bridge object tells us whether the
> OS is permitted to deviate from the resource assignment configured by
> the firmware. If this is not the case, we should not permit drivers to
> resize BARs on the fly. So make pci_resize_resource() take this into
> account.
> 
> Cc: <stable@...r.kernel.org> # v5.4+
> Signed-off-by: Ard Biesheuvel <ardb@...nel.org>

Capitalized subject to match convention and applied to pci/resource
for v5.11, thanks!

Is there an email, bug report, etc that prompted this change?

> ---
>  drivers/pci/setup-res.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/drivers/pci/setup-res.c b/drivers/pci/setup-res.c
> index 43eda101fcf4..3b38be081e93 100644
> --- a/drivers/pci/setup-res.c
> +++ b/drivers/pci/setup-res.c
> @@ -410,10 +410,16 @@ EXPORT_SYMBOL(pci_release_resource);
>  int pci_resize_resource(struct pci_dev *dev, int resno, int size)
>  {
>  	struct resource *res = dev->resource + resno;
> +	struct pci_host_bridge *host;
>  	int old, ret;
>  	u32 sizes;
>  	u16 cmd;
>  
> +	/* Check if we must preserve the firmware's resource assignment */
> +	host = pci_find_host_bridge(dev->bus);
> +	if (host->preserve_config)
> +		return -ENOTSUPP;
> +
>  	/* Make sure the resource isn't assigned before resizing it. */
>  	if (!(res->flags & IORESOURCE_UNSET))
>  		return -EBUSY;
> -- 
> 2.17.1
>