Re: [PATCH 11/21] KVM: x86/MMU: Cleanup shrinker interface with Shadow MMU

[kernel test robot]

Hi Ben,

Thank you for the patch! Perhaps something to improve:

[auto build test WARNING on 7cb79f433e75b05d1635aefaa851cfcd1cb7dc4f]

url:    https://github.com/intel-lab-lkp/linux/commits/Ben-Gardon/KVM-x86-mmu-Rename-slot-rmap-walkers-to-add-clarity-and-clean-up-code/20230203-023259
base:   7cb79f433e75b05d1635aefaa851cfcd1cb7dc4f
patch link:    https://lore.kernel.org/r/20230202182809.1929122-12-bgardon%40google.com
patch subject: [PATCH 11/21] KVM: x86/MMU: Cleanup shrinker interface with Shadow MMU
config: x86_64-randconfig-a002 (https://download.01.org/0day-ci/archive/20230204/202302042127.gbKNDVaL-lkp@xxxxxxxxx/config)
compiler: gcc-11 (Debian 11.3.0-8) 11.3.0
reproduce (this is a W=1 build):
        # https://github.com/intel-lab-lkp/linux/commit/c1170de906dfe1ee64da0066e7c28d35e716ed18
        git remote add linux-review https://github.com/intel-lab-lkp/linux
        git fetch --no-tags linux-review Ben-Gardon/KVM-x86-mmu-Rename-slot-rmap-walkers-to-add-clarity-and-clean-up-code/20230203-023259
        git checkout c1170de906dfe1ee64da0066e7c28d35e716ed18
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        make W=1 O=build_dir ARCH=x86_64 olddefconfig
        make W=1 O=build_dir ARCH=x86_64 SHELL=/bin/bash arch/x86/kvm/

If you fix the issue, kindly add following tag where applicable
| Reported-by: kernel test robot <lkp@xxxxxxxxx>

All warnings (new ones prefixed by >>):

>> arch/x86/kvm/mmu/mmu.c:3148:15: warning: no previous prototype for 'mmu_shrink_scan' [-Wmissing-prototypes]
    3148 | unsigned long mmu_shrink_scan(struct shrinker *shrink, struct shrink_control *sc)
         |               ^~~~~~~~~~~~~~~


vim +/mmu_shrink_scan +3148 arch/x86/kvm/mmu/mmu.c

  3147	
> 3148	unsigned long mmu_shrink_scan(struct shrinker *shrink, struct shrink_control *sc)
  3149	{
  3150		struct kvm *kvm;
  3151		int nr_to_scan = sc->nr_to_scan;
  3152		unsigned long freed = 0;
  3153	
  3154		mutex_lock(&kvm_lock);
  3155	
  3156		list_for_each_entry(kvm, &vm_list, vm_list) {
  3157			/*
  3158			 * Never scan more than sc->nr_to_scan VM instances.
  3159			 * Will not hit this condition practically since we do not try
  3160			 * to shrink more than one VM and it is very unlikely to see
  3161			 * !n_used_mmu_pages so many times.
  3162			 */
  3163			if (!nr_to_scan--)
  3164				break;
  3165	
  3166			/*
  3167			 * n_used_mmu_pages is accessed without holding kvm->mmu_lock
  3168			 * here. We may skip a VM instance errorneosly, but we do not
  3169			 * want to shrink a VM that only started to populate its MMU
  3170			 * anyway.
  3171			 */
  3172			if (!kvm->arch.n_used_mmu_pages &&
  3173			    !kvm_shadow_mmu_has_zapped_obsolete_pages(kvm))
  3174				continue;
  3175	
  3176			freed = kvm_shadow_mmu_shrink_scan(kvm, sc->nr_to_scan);
  3177	
  3178			/*
  3179			 * unfair on small ones
  3180			 * per-vm shrinkers cry out
  3181			 * sadness comes quickly
  3182			 */
  3183			list_move_tail(&kvm->vm_list, &vm_list);
  3184			break;
  3185		}
  3186	
  3187		mutex_unlock(&kvm_lock);
  3188		return freed;
  3189	}
  3190	

-- 
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https://github.com/intel/lkp-tests