Hi linmiaohe, Thank you for the patch! Perhaps something to improve: [auto build test WARNING on kvm/linux-next] [also build test WARNING on v5.5-rc7 next-20200124] [if your patch is applied to the wrong git tree, please drop us a note to help improve the system. BTW, we also suggest to use '--base' option to specify the base tree in git format-patch, please see https://stackoverflow.com/a/37406982] url: https://github.com/0day-ci/linux/commits/linmiaohe/KVM-x86-avoid-some-unnecessary-copy-in-__x86_set_memory_region/20200125-020112 base: https://git.kernel.org/pub/scm/virt/kvm/kvm.git linux-next config: i386-allyesconfig (attached as .config) compiler: gcc-7 (Debian 7.5.0-3) 7.5.0 reproduce: # save the attached .config to linux build tree make ARCH=i386 If you fix the issue, kindly add following tag Reported-by: kbuild test robot <lkp@xxxxxxxxx> Note: it may well be a FALSE warning. FWIW you are at least aware of it now. http://gcc.gnu.org/wiki/Better_Uninitialized_Warnings All warnings (new ones prefixed by >>): In file included from arch/x86/kvm/x86.c:25:0: arch/x86/kvm/x86.h: In function 'kvm_dr7_valid': arch/x86/kvm/x86.h:363:16: warning: right shift count >= width of type [-Wshift-count-overflow] return !(data >> 32); ^~ arch/x86/kvm/x86.c: In function '__x86_set_memory_region': >> arch/x86/kvm/x86.c:9730:27: warning: 'npages' may be used uninitialized in this function [-Wmaybe-uninitialized] vm_munmap(uaddr, npages * PAGE_SIZE); >> arch/x86/kvm/x86.c:9730:3: warning: 'uaddr' may be used uninitialized in this function [-Wmaybe-uninitialized] vm_munmap(uaddr, npages * PAGE_SIZE); ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ vim +/npages +9730 arch/x86/kvm/x86.c 9682 9683 int __x86_set_memory_region(struct kvm *kvm, int id, gpa_t gpa, u32 size) 9684 { 9685 int i, r; 9686 unsigned long hva, uaddr, npages; 9687 struct kvm_memslots *slots = kvm_memslots(kvm); 9688 struct kvm_memory_slot *slot; 9689 9690 /* Called with kvm->slots_lock held. */ 9691 if (WARN_ON(id >= KVM_MEM_SLOTS_NUM)) 9692 return -EINVAL; 9693 9694 slot = id_to_memslot(slots, id); 9695 if (size) { 9696 if (slot->npages) 9697 return -EEXIST; 9698 9699 /* 9700 * MAP_SHARED to prevent internal slot pages from being moved 9701 * by fork()/COW. 9702 */ 9703 hva = vm_mmap(NULL, 0, size, PROT_READ | PROT_WRITE, 9704 MAP_SHARED | MAP_ANONYMOUS, 0); 9705 if (IS_ERR((void *)hva)) 9706 return PTR_ERR((void *)hva); 9707 } else { 9708 if (!slot->npages) 9709 return 0; 9710 9711 hva = 0; 9712 uaddr = slot->userspace_addr; 9713 npages = slot->npages; 9714 } 9715 9716 for (i = 0; i < KVM_ADDRESS_SPACE_NUM; i++) { 9717 struct kvm_userspace_memory_region m; 9718 9719 m.slot = id | (i << 16); 9720 m.flags = 0; 9721 m.guest_phys_addr = gpa; 9722 m.userspace_addr = hva; 9723 m.memory_size = size; 9724 r = __kvm_set_memory_region(kvm, &m); 9725 if (r < 0) 9726 return r; 9727 } 9728 9729 if (!size) > 9730 vm_munmap(uaddr, npages * PAGE_SIZE); 9731 9732 return 0; 9733 } 9734 EXPORT_SYMBOL_GPL(__x86_set_memory_region); 9735 --- 0-DAY kernel test infrastructure Open Source Technology Center https://lists.01.org/hyperkitty/list/kbuild-all@xxxxxxxxxxxx Intel Corporation
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