Re: [PATCH v1 2/4] x86/process: Add a debug interface to change LAM tag width

[kernel test robot <lkp@intel.com>]

Hi Maciej,

kernel test robot noticed the following build warnings:

[auto build test WARNING on tip/x86/core]
[also build test WARNING on peterz-queue/sched/core akpm-mm/mm-everything linus/master v6.19 next-20260220]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Maciej-Wieczor-Retman/x86-process-Shorten-the-default-LAM-tag-width/20260220-205155
base:   tip/x86/core
patch link:    https://lore.kernel.org/r/5ed38af72848015f3417c462e624e52891dc14ed.1771589807.git.m.wieczorretman%40pm.me
patch subject: [PATCH v1 2/4] x86/process: Add a debug interface to change LAM tag width
config: x86_64-buildonly-randconfig-001-20260220 (https://download.01.org/0day-ci/archive/20260221/202602210040.C4PVoS0u-lkp@intel.com/config)
compiler: clang version 20.1.8 (https://github.com/llvm/llvm-project 87f0227cb60147a26a1eeb4fb06e3b505e9c7261)
rustc: rustc 1.88.0 (6b00bc388 2025-06-23)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260221/202602210040.C4PVoS0u-lkp@intel.com/reproduce)

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
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202602210040.C4PVoS0u-lkp@intel.com/

All warnings (new ones prefixed by >>):

   arch/x86/kernel/process_64.c:812:8: warning: 'sprintf' will always overflow; destination buffer has size 2, but format string expands to at least 3 [-Wformat-overflow]
     812 |         len = sprintf(buf, "%ld\n", lam_available_bits);
         |               ^
>> arch/x86/kernel/process_64.c:827:6: warning: unused variable 'ceiling' [-Wunused-variable]
     827 |         int ceiling;
         |             ^~~~~~~
   2 warnings generated.


vim +/ceiling +827 arch/x86/kernel/process_64.c

   815	
   816	/*
   817	 * Writing a number to this file changes the used lam tag width. Valid values
   818	 * are 4 bit tag width and 6 bit tag width - the second, non-default one is
   819	 * meant mostly for debug and shall be deprecated in the future.
   820	 */
   821	static ssize_t lam_bits_write_file(struct file *file,
   822					   const char __user *user_buf, size_t count,
   823					   loff_t *ppos)
   824	{
   825		char buf[32];
   826		ssize_t len;
 > 827		int ceiling;
   828		u8 bits;
   829	
   830		len = min(count, sizeof(buf) - 1);
   831		if (copy_from_user(buf, user_buf, len))
   832			return -EFAULT;
   833	
   834		buf[len] = '\0';
   835		if (kstrtou8(buf, 0, &bits))
   836			return -EINVAL;
   837	
   838		switch (bits) {
   839		case LAM_DEFAULT_BITS:
   840		case LAM_MAX_BITS:
   841			lam_available_bits = bits;
   842			return count;
   843		default:
   844			return -EINVAL;
   845		}
   846	}
   847	

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