Re: [PATCH RFC 09/15] arm_mpam: Fix MSC MMIO window size to use resource_size() instead of end - start

[Ben Horgan]

Hi Yin,

On 11/08/2026 14:30, Yin Li wrote:
> struct resource uses an inclusive end address, so the correct size is
> end - start + 1. The previous calculation of end - start was off by one,
> resulting in a mapped window one byte smaller than the actual resource.
> Use resource_size() which correctly computes end - start + 1.
> 
> Signed-off-by: Yin Li <yin.li@xxxxxxxxxxxxxxxx>

I just got a kernel ci report for this one which asks for tags:

Reported-by: kernel test robot <lkp@xxxxxxxxx>
Closes: https://lore.kernel.org/oe-kbuild-all/202609030809.ObirDhR3-lkp@xxxxxxxxx/

It doesn't look to give a useful fixes tag though. I'd go with this as that's where the error was
introduced.

Fixes: f04046f2577a ("arm_mpam: Add probe/remove for mpam msc driver and kbuild boiler plate")

Looks good to me.

Reviewed-by: Ben Horgan <ben.horgan@xxxxxxx>

Thanks,

Ben

> ---
>  drivers/resctrl/mpam_devices.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/resctrl/mpam_devices.c b/drivers/resctrl/mpam_devices.c
> index 1e082fb60e30..5d1854d97371 100644
> --- a/drivers/resctrl/mpam_devices.c
> +++ b/drivers/resctrl/mpam_devices.c
> @@ -2296,7 +2296,7 @@ static struct mpam_msc *do_mpam_msc_drv_probe(struct platform_device *pdev)
>  			dev_err_once(dev, "Failed to map MSC base address\n");
>  			return ERR_CAST(io);
>  		}
> -		msc->mapped_hwpage_sz = msc_res->end - msc_res->start;
> +		msc->mapped_hwpage_sz = resource_size(msc_res);
>  		msc->mapped_hwpage = io;
>  	} else {
>  		return ERR_PTR(-EINVAL);
>