Hi Steven,

[FYI, it's a private test report for your RFC patch.]
[auto build test WARNING on arm64/for-next/core]
[also build test WARNING on v5.11-rc3]
[cannot apply to kvmarm/next kvm/linux-next next-20210115]
[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]

url:    https://github.com/0day-ci/linux/commits/Steven-Price/MTE-support-for-KVM-guest/20210115-233109
base:   https://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-next/core
config: arm64-allyesconfig (attached as .config)
compiler: aarch64-linux-gcc (GCC) 9.3.0
reproduce (this is a W=1 build):
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # https://github.com/0day-ci/linux/commit/ddde8cff287aad027c9fa0015afe26ced5041f50
        git remote add linux-review https://github.com/0day-ci/linux
        git fetch --no-tags linux-review Steven-Price/MTE-support-for-KVM-guest/20210115-233109
        git checkout ddde8cff287aad027c9fa0015afe26ced5041f50
        # save the attached .config to linux build tree
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-9.3.0 make.cross ARCH=arm64 

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@intel.com>

All warnings (new ones prefixed by >>):

   arch/arm64/kvm/arm.c: In function 'kvm_vm_ioctl_mte_copy_tags':
>> arch/arm64/kvm/arm.c:1313:9: warning: variable 'pages' set but not used [-Wunused-but-set-variable]
    1313 |  size_t pages;
         |         ^~~~~


vim +/pages +1313 arch/arm64/kvm/arm.c

  1305	
  1306	static int kvm_vm_ioctl_mte_copy_tags(struct kvm *kvm,
  1307					      struct kvm_arm_copy_mte_tags *copy_tags)
  1308	{
  1309		gpa_t guest_ipa = copy_tags->guest_ipa;
  1310		size_t length = copy_tags->length;
  1311		void __user *tags = copy_tags->addr;
  1312		gpa_t gfn;
> 1313		size_t pages;
  1314		bool write = !(copy_tags->flags & KVM_ARM_TAGS_FROM_GUEST);
  1315	
  1316		if (copy_tags->flags & ~KVM_ARM_TAGS_FROM_GUEST)
  1317			return -EINVAL;
  1318	
  1319		if (length & ~PAGE_MASK || guest_ipa & ~PAGE_MASK)
  1320			return -EINVAL;
  1321	
  1322		gfn = gpa_to_gfn(guest_ipa);
  1323		pages = length >> PAGE_SHIFT;
  1324	
  1325		while (length > 0) {
  1326			kvm_pfn_t pfn = gfn_to_pfn_prot(kvm, gfn, write, NULL);
  1327			void *maddr;
  1328			unsigned long num_tags = PAGE_SIZE / MTE_GRANULE_SIZE;
  1329	
  1330			if (is_error_noslot_pfn(pfn))
  1331				return -ENOENT;
  1332	
  1333			maddr = page_address(pfn_to_page(pfn));
  1334	
  1335			if (!write) {
  1336				num_tags = mte_copy_tags_to_user(tags, maddr, num_tags);
  1337				kvm_release_pfn_clean(pfn);
  1338			} else {
  1339				num_tags = mte_copy_tags_from_user(maddr, tags,
  1340								   num_tags);
  1341				kvm_release_pfn_dirty(pfn);
  1342			}
  1343	
  1344			if (num_tags != PAGE_SIZE / MTE_GRANULE_SIZE)
  1345				return -EFAULT;
  1346	
  1347			gfn++;
  1348			tags += num_tags;
  1349			length -= PAGE_SIZE;
  1350		}
  1351	
  1352		return 0;
  1353	}
  1354	

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all(a)lists.01.org