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

From: kernel test robot <lkp@intel.com>
To: Ben Gardon <bgardon@google.com>,
	linux-kernel@vger.kernel.org, kvm@vger.kernel.org
Cc: llvm@lists.linux.dev, oe-kbuild-all@lists.linux.dev,
	Paolo Bonzini <pbonzini@redhat.com>, Peter Xu <peterx@redhat.com>,
	Sean Christopherson <seanjc@google.com>,
	David Matlack <dmatlack@google.com>,
	Vipin Sharma <vipinsh@google.com>,
	Ricardo Koller <ricarkol@google.com>,
	Ben Gardon <bgardon@google.com>
Subject: Re: [PATCH 11/21] KVM: x86/MMU: Cleanup shrinker interface with Shadow MMU
Date: Sun, 5 Feb 2023 03:10:35 +0800	[thread overview]
Message-ID: <202302050303.kLjMucYK-lkp@intel.com> (raw)
In-Reply-To: <20230202182809.1929122-12-bgardon@google.com>

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-a014 (https://download.01.org/0day-ci/archive/20230205/202302050303.kLjMucYK-lkp@intel.com/config)
compiler: clang version 14.0.6 (https://github.com/llvm/llvm-project f28c006a5895fc0e329fe15fead81e37457cb1d1)
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/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
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 O=build_dir ARCH=x86_64 olddefconfig
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross 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@intel.com>

All warnings (new ones prefixed by >>):

>> arch/x86/kvm/mmu/mmu.c:3148:15: warning: no previous prototype for function 'mmu_shrink_scan' [-Wmissing-prototypes]
   unsigned long mmu_shrink_scan(struct shrinker *shrink, struct shrink_control *sc)
                 ^
   arch/x86/kvm/mmu/mmu.c:3148:1: note: declare 'static' if the function is not intended to be used outside of this translation unit
   unsigned long mmu_shrink_scan(struct shrinker *shrink, struct shrink_control *sc)
   ^
   static 
   1 warning generated.

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	

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