drivers/resctrl/mpam_devices.c:1860:35-38: WARNING: Suspicious code. resource_size is maybe missing with msc_res

drivers/resctrl/mpam_devices.c:1860:35-38: WARNING: Suspicious code. resource_size is maybe missing with msc_res

[kernel test robot]

Hi Ben,

First bad commit (maybe != root cause):

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
head:   89a312991dc6e638a36adc43ccb91dbc25504c04
commit: c544f00a473239835d22e7109b403314d8b85974 arm64: mpam: Drop the CONFIG_EXPERT restriction
date:   5 months ago
config: arm64-randconfig-r051-20260902 (https://download.01.org/0day-ci/archive/20260903/202609030809.ObirDhR3-lkp@intel.com/config)
compiler: clang version 24.0.0git (https://github.com/llvm/llvm-project 2c2cffa015e9549aafba9e514384b08204c7cc4b)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Fixes: c544f00a4732 ("arm64: mpam: Drop the CONFIG_EXPERT restriction")
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202609030809.ObirDhR3-lkp@intel.com/

cocci warnings: (new ones prefixed by >>)
>> drivers/resctrl/mpam_devices.c:1860:35-38: WARNING: Suspicious code. resource_size is maybe missing with msc_res

vim +1860 drivers/resctrl/mpam_devices.c

f04046f2577a5c James Morse 2025-11-19  1797  
f04046f2577a5c James Morse 2025-11-19  1798  static struct mpam_msc *do_mpam_msc_drv_probe(struct platform_device *pdev)
f04046f2577a5c James Morse 2025-11-19  1799  {
f04046f2577a5c James Morse 2025-11-19  1800  	int err;
f04046f2577a5c James Morse 2025-11-19  1801  	u32 tmp;
f04046f2577a5c James Morse 2025-11-19  1802  	struct mpam_msc *msc;
f04046f2577a5c James Morse 2025-11-19  1803  	struct resource *msc_res;
f04046f2577a5c James Morse 2025-11-19  1804  	struct device *dev = &pdev->dev;
f04046f2577a5c James Morse 2025-11-19  1805  
f04046f2577a5c James Morse 2025-11-19  1806  	lockdep_assert_held(&mpam_list_lock);
f04046f2577a5c James Morse 2025-11-19  1807  
f04046f2577a5c James Morse 2025-11-19  1808  	msc = devm_kzalloc(&pdev->dev, sizeof(*msc), GFP_KERNEL);
f04046f2577a5c James Morse 2025-11-19  1809  	if (!msc)
f04046f2577a5c James Morse 2025-11-19  1810  		return ERR_PTR(-ENOMEM);
01fb4b8224726a James Morse 2025-11-19  1811  	init_garbage(&msc->garbage);
01fb4b8224726a James Morse 2025-11-19  1812  	msc->garbage.pdev = pdev;
f04046f2577a5c James Morse 2025-11-19  1813  
f04046f2577a5c James Morse 2025-11-19  1814  	err = devm_mutex_init(dev, &msc->probe_lock);
f04046f2577a5c James Morse 2025-11-19  1815  	if (err)
f04046f2577a5c James Morse 2025-11-19  1816  		return ERR_PTR(err);
f04046f2577a5c James Morse 2025-11-19  1817  
f04046f2577a5c James Morse 2025-11-19  1818  	err = devm_mutex_init(dev, &msc->part_sel_lock);
f04046f2577a5c James Morse 2025-11-19  1819  	if (err)
f04046f2577a5c James Morse 2025-11-19  1820  		return ERR_PTR(err);
f04046f2577a5c James Morse 2025-11-19  1821  
49aa621c4dcaf8 James Morse 2025-11-19  1822  	err = devm_mutex_init(dev, &msc->error_irq_lock);
49aa621c4dcaf8 James Morse 2025-11-19  1823  	if (err)
49aa621c4dcaf8 James Morse 2025-11-19  1824  		return ERR_PTR(err);
09b89d2a72f37b James Morse 2025-11-19  1825  
09b89d2a72f37b James Morse 2025-11-19  1826  	err = devm_mutex_init(dev, &msc->cfg_lock);
09b89d2a72f37b James Morse 2025-11-19  1827  	if (err)
09b89d2a72f37b James Morse 2025-11-19  1828  		return ERR_PTR(err);
09b89d2a72f37b James Morse 2025-11-19  1829  
d02beb06ca2a62 James Morse 2025-11-19  1830  	mpam_mon_sel_lock_init(msc);
f04046f2577a5c James Morse 2025-11-19  1831  	msc->id = pdev->id;
f04046f2577a5c James Morse 2025-11-19  1832  	msc->pdev = pdev;
f04046f2577a5c James Morse 2025-11-19  1833  	INIT_LIST_HEAD_RCU(&msc->all_msc_list);
f04046f2577a5c James Morse 2025-11-19  1834  	INIT_LIST_HEAD_RCU(&msc->ris);
f04046f2577a5c James Morse 2025-11-19  1835  
f04046f2577a5c James Morse 2025-11-19  1836  	update_msc_accessibility(msc);
f04046f2577a5c James Morse 2025-11-19  1837  	if (cpumask_empty(&msc->accessibility)) {
f04046f2577a5c James Morse 2025-11-19  1838  		dev_err_once(dev, "MSC is not accessible from any CPU!");
f04046f2577a5c James Morse 2025-11-19  1839  		return ERR_PTR(-EINVAL);
f04046f2577a5c James Morse 2025-11-19  1840  	}
f04046f2577a5c James Morse 2025-11-19  1841  
49aa621c4dcaf8 James Morse 2025-11-19  1842  	err = mpam_msc_setup_error_irq(msc);
49aa621c4dcaf8 James Morse 2025-11-19  1843  	if (err)
49aa621c4dcaf8 James Morse 2025-11-19  1844  		return ERR_PTR(err);
49aa621c4dcaf8 James Morse 2025-11-19  1845  
f04046f2577a5c James Morse 2025-11-19  1846  	if (device_property_read_u32(&pdev->dev, "pcc-channel", &tmp))
f04046f2577a5c James Morse 2025-11-19  1847  		msc->iface = MPAM_IFACE_MMIO;
f04046f2577a5c James Morse 2025-11-19  1848  	else
f04046f2577a5c James Morse 2025-11-19  1849  		msc->iface = MPAM_IFACE_PCC;
f04046f2577a5c James Morse 2025-11-19  1850  
f04046f2577a5c James Morse 2025-11-19  1851  	if (msc->iface == MPAM_IFACE_MMIO) {
f04046f2577a5c James Morse 2025-11-19  1852  		void __iomem *io;
f04046f2577a5c James Morse 2025-11-19  1853  
f04046f2577a5c James Morse 2025-11-19  1854  		io = devm_platform_get_and_ioremap_resource(pdev, 0,
f04046f2577a5c James Morse 2025-11-19  1855  							    &msc_res);
f04046f2577a5c James Morse 2025-11-19  1856  		if (IS_ERR(io)) {
f04046f2577a5c James Morse 2025-11-19  1857  			dev_err_once(dev, "Failed to map MSC base address\n");
f04046f2577a5c James Morse 2025-11-19  1858  			return ERR_CAST(io);
f04046f2577a5c James Morse 2025-11-19  1859  		}
f04046f2577a5c James Morse 2025-11-19 @1860  		msc->mapped_hwpage_sz = msc_res->end - msc_res->start;
f04046f2577a5c James Morse 2025-11-19  1861  		msc->mapped_hwpage = io;
f04046f2577a5c James Morse 2025-11-19  1862  	} else {
f04046f2577a5c James Morse 2025-11-19  1863  		return ERR_PTR(-EINVAL);
f04046f2577a5c James Morse 2025-11-19  1864  	}
f04046f2577a5c James Morse 2025-11-19  1865  
f04046f2577a5c James Morse 2025-11-19  1866  	list_add_rcu(&msc->all_msc_list, &mpam_all_msc);
f04046f2577a5c James Morse 2025-11-19  1867  	platform_set_drvdata(pdev, msc);
f04046f2577a5c James Morse 2025-11-19  1868  
f04046f2577a5c James Morse 2025-11-19  1869  	return msc;
f04046f2577a5c James Morse 2025-11-19  1870  }
f04046f2577a5c James Morse 2025-11-19  1871  

:::::: The code at line 1860 was first introduced by commit
:::::: f04046f2577a5c76167333ca99d3903ee5331ba0 arm_mpam: Add probe/remove for mpam msc driver and kbuild boiler plate

:::::: TO: James Morse <james.morse@arm.com>
:::::: CC: Catalin Marinas <catalin.marinas@arm.com>

--
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki

Re: drivers/resctrl/mpam_devices.c:1860:35-38: WARNING: Suspicious code. resource_size is maybe missing with msc_res

[Ilpo Järvinen]

On Thu, 3 Sep 2026, kernel test robot wrote:

> Hi Ben,
> 
> First bad commit (maybe != root cause):
> 
> tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
> head:   89a312991dc6e638a36adc43ccb91dbc25504c04
> commit: c544f00a473239835d22e7109b403314d8b85974 arm64: mpam: Drop the CONFIG_EXPERT restriction
> date:   5 months ago
> config: arm64-randconfig-r051-20260902 (https://download.01.org/0day-ci/archive/20260903/202609030809.ObirDhR3-lkp@intel.com/config)
> compiler: clang version 24.0.0git (https://github.com/llvm/llvm-project 2c2cffa015e9549aafba9e514384b08204c7cc4b)
> 
> If you fix the issue in a separate patch/commit (i.e. not just a new version of
> the same patch/commit), kindly add following tags
> | Fixes: c544f00a4732 ("arm64: mpam: Drop the CONFIG_EXPERT restriction")
> | Reported-by: kernel test robot <lkp@intel.com>
> | Closes: https://lore.kernel.org/oe-kbuild-all/202609030809.ObirDhR3-lkp@intel.com/
> 
> cocci warnings: (new ones prefixed by >>)
> >> drivers/resctrl/mpam_devices.c:1860:35-38: WARNING: Suspicious code. resource_size is maybe missing with msc_res
> 
> vim +1860 drivers/resctrl/mpam_devices.c
> 
> f04046f2577a5c James Morse 2025-11-19 @1860  		msc->mapped_hwpage_sz = msc_res->end - msc_res->start;

> :::::: The code at line 1860 was first introduced by commit
> :::::: f04046f2577a5c76167333ca99d3903ee5331ba0 arm_mpam: Add probe/remove for mpam msc driver and kbuild boiler plate
> 
> :::::: TO: James Morse <james.morse@arm.com>
> :::::: CC: Catalin Marinas <catalin.marinas@arm.com>

Hi all,

This report has some validity but the code doesn't look buggy as is, just 
off-by-one errors correcting each other. The variable is called "..._sz" 
(~ size), but the resource size calculation is off-by-one because trying 
to do it by hand instead of using the resource_size() helper.

The mapped_hwpage_sz value is only used for register write offset 
sanity checks, which use > countering the off-by-one error.

IMO, it would be better to use resource_size() and change those sanity 
checks to use >= instead of > but this doesn't look a major problem by 
any means.

-- 
 i.

Re: drivers/resctrl/mpam_devices.c:1860:35-38: WARNING: Suspicious code. resource_size is maybe missing with msc_res

[Ben Horgan]

Hi Ilpo,

On 03/09/2026 12:02, Ilpo Järvinen wrote:
> On Thu, 3 Sep 2026, kernel test robot wrote:
> 
>> Hi Ben,
>>
>> First bad commit (maybe != root cause):
>>
>> tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
>> head:   89a312991dc6e638a36adc43ccb91dbc25504c04
>> commit: c544f00a473239835d22e7109b403314d8b85974 arm64: mpam: Drop the CONFIG_EXPERT restriction
>> date:   5 months ago
>> config: arm64-randconfig-r051-20260902 (https://download.01.org/0day-ci/archive/20260903/202609030809.ObirDhR3-lkp@intel.com/config)
>> compiler: clang version 24.0.0git (https://github.com/llvm/llvm-project 2c2cffa015e9549aafba9e514384b08204c7cc4b)
>>
>> If you fix the issue in a separate patch/commit (i.e. not just a new version of
>> the same patch/commit), kindly add following tags
>> | Fixes: c544f00a4732 ("arm64: mpam: Drop the CONFIG_EXPERT restriction")
>> | Reported-by: kernel test robot <lkp@intel.com>
>> | Closes: https://lore.kernel.org/oe-kbuild-all/202609030809.ObirDhR3-lkp@intel.com/
>>
>> cocci warnings: (new ones prefixed by >>)
>>>> drivers/resctrl/mpam_devices.c:1860:35-38: WARNING: Suspicious code. resource_size is maybe missing with msc_res
>>
>> vim +1860 drivers/resctrl/mpam_devices.c
>>
>> f04046f2577a5c James Morse 2025-11-19 @1860  		msc->mapped_hwpage_sz = msc_res->end - msc_res->start;
> 
>> :::::: The code at line 1860 was first introduced by commit
>> :::::: f04046f2577a5c76167333ca99d3903ee5331ba0 arm_mpam: Add probe/remove for mpam msc driver and kbuild boiler plate
>>
>> :::::: TO: James Morse <james.morse@arm.com>
>> :::::: CC: Catalin Marinas <catalin.marinas@arm.com>
> 
> Hi all,
> 
> This report has some validity but the code doesn't look buggy as is, just 
> off-by-one errors correcting each other. The variable is called "..._sz" 
> (~ size), but the resource size calculation is off-by-one because trying Arm A-profile Architecture Hi 
> to do it by hand instead of using the resource_size() helper.
> 
> The mapped_hwpage_sz value is only used for register write offset 
> sanity checks, which use > countering the off-by-one error.

Ah, yes, thanks for pointing this out. mapped_hwpage_sz is a misleading name as it really indicates
the last byte mapped and so it is functionally correct when used with >.

> 
> IMO, it would be better to use resource_size() and change those sanity 
> checks to use >= instead of > but this doesn't look a major problem by 
> any means.

Agreed. Looking back I fixed the functional bug in v6 (changed >= to >) of the original mpam driver
posting but left it in a confusing state.

Thanks,

Ben

>