[kvms390:next 21/32] arch/s390/kvm/s390/../gmap/kvm_mmu.c:64 s390_kvm_mmu_prepare_memory_region() error: we previously assumed 'new' could be null (see line 50)

BCC: [email protected]
CC: [email protected]
CC: [email protected]
TO: Steffen Eiden <[email protected]>
CC: Christian Borntraeger <[email protected]>

Hi Steffen,

FYI, the error/warning was bisected to this commit, please ignore it if it's irrelevant.

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/kvms390/linux.git next
head:   dd6f4ef6f8a37412909ad787c837332fb070159c
commit: d487a24041c2ea9999ff6e8384002b874de64c94 [21/32] KVM: s390: Prepare gmap for a second KVM implementation
:::::: branch date: 26 hours ago
:::::: commit date: 33 hours ago
config: s390-randconfig-r071-20260814 (https://download.01.org/0day-ci/archive/20260815/[email protected]/config)
compiler: s390-linux-gcc (GCC) 9.5.0
smatch: v0.5.0-9187-g5189e3fb

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 <[email protected]>
| Reported-by: Dan Carpenter <[email protected]>
| Closes: https://lore.kernel.org/r/[email protected]/

smatch warnings:
arch/s390/kvm/s390/../gmap/kvm_mmu.c:64 s390_kvm_mmu_prepare_memory_region() error: we previously assumed 'new' could be null (see line 50)

vim +/new +64 arch/s390/kvm/s390/../gmap/kvm_mmu.c

d487a24041c2ea9 Steffen Eiden 2026-04-02  44  
d487a24041c2ea9 Steffen Eiden 2026-04-02  45  int s390_kvm_mmu_prepare_memory_region(struct kvm *kvm,
d487a24041c2ea9 Steffen Eiden 2026-04-02  46  				       const struct kvm_memory_slot *old,
d487a24041c2ea9 Steffen Eiden 2026-04-02  47  				       struct kvm_memory_slot *new,
d487a24041c2ea9 Steffen Eiden 2026-04-02  48  				       enum kvm_mr_change change)
d487a24041c2ea9 Steffen Eiden 2026-04-02  49  {
d487a24041c2ea9 Steffen Eiden 2026-04-02 @50  	if (kvm_is_ucontrol(kvm) && new && new->id < KVM_USER_MEM_SLOTS)
d487a24041c2ea9 Steffen Eiden 2026-04-02  51  		return -EINVAL;
d487a24041c2ea9 Steffen Eiden 2026-04-02  52  
d487a24041c2ea9 Steffen Eiden 2026-04-02  53  	/* When we are protected, we should not change the memory slots */
d487a24041c2ea9 Steffen Eiden 2026-04-02  54  	if (kvm_s390_pv_get_handle(kvm))
d487a24041c2ea9 Steffen Eiden 2026-04-02  55  		return -EINVAL;
d487a24041c2ea9 Steffen Eiden 2026-04-02  56  
d487a24041c2ea9 Steffen Eiden 2026-04-02  57  	if (change != KVM_MR_DELETE && change != KVM_MR_FLAGS_ONLY) {
d487a24041c2ea9 Steffen Eiden 2026-04-02  58  		/*
d487a24041c2ea9 Steffen Eiden 2026-04-02  59  		 * A few sanity checks. The memory in userland is ok to be
d487a24041c2ea9 Steffen Eiden 2026-04-02  60  		 * fragmented into various different vmas. It is okay to mmap()
d487a24041c2ea9 Steffen Eiden 2026-04-02  61  		 * and munmap() stuff in this slot after doing this call at any
d487a24041c2ea9 Steffen Eiden 2026-04-02  62  		 * time.
d487a24041c2ea9 Steffen Eiden 2026-04-02  63  		 */
d487a24041c2ea9 Steffen Eiden 2026-04-02 @64  		if (new->userspace_addr & ~PAGE_MASK)
d487a24041c2ea9 Steffen Eiden 2026-04-02  65  			return -EINVAL;
d487a24041c2ea9 Steffen Eiden 2026-04-02  66  		if ((new->base_gfn + new->npages) * PAGE_SIZE > kvm->arch.mem_limit)
d487a24041c2ea9 Steffen Eiden 2026-04-02  67  			return -EINVAL;
d487a24041c2ea9 Steffen Eiden 2026-04-02  68  		if (!asce_contains_gfn(kvm->arch.gmap->asce, new->base_gfn + new->npages - 1))
d487a24041c2ea9 Steffen Eiden 2026-04-02  69  			return -EINVAL;
d487a24041c2ea9 Steffen Eiden 2026-04-02  70  	}
d487a24041c2ea9 Steffen Eiden 2026-04-02  71  
d487a24041c2ea9 Steffen Eiden 2026-04-02  72  	if (!kvm_s390_is_migration_mode(kvm))
d487a24041c2ea9 Steffen Eiden 2026-04-02  73  		return 0;
d487a24041c2ea9 Steffen Eiden 2026-04-02  74  
d487a24041c2ea9 Steffen Eiden 2026-04-02  75  	/*
d487a24041c2ea9 Steffen Eiden 2026-04-02  76  	 * Turn off migration mode when:
d487a24041c2ea9 Steffen Eiden 2026-04-02  77  	 * - userspace creates a new memslot with dirty logging off,
d487a24041c2ea9 Steffen Eiden 2026-04-02  78  	 * - userspace modifies an existing memslot (MOVE or FLAGS_ONLY) and
d487a24041c2ea9 Steffen Eiden 2026-04-02  79  	 *   dirty logging is turned off.
d487a24041c2ea9 Steffen Eiden 2026-04-02  80  	 * Migration mode expects dirty page logging being enabled to store
d487a24041c2ea9 Steffen Eiden 2026-04-02  81  	 * its dirty bitmap.
d487a24041c2ea9 Steffen Eiden 2026-04-02  82  	 */
d487a24041c2ea9 Steffen Eiden 2026-04-02  83  	if (change != KVM_MR_DELETE &&
d487a24041c2ea9 Steffen Eiden 2026-04-02  84  	    !(new->flags & KVM_MEM_LOG_DIRTY_PAGES))
d487a24041c2ea9 Steffen Eiden 2026-04-02  85  		WARN(kvm_s390_vm_stop_migration(kvm),
d487a24041c2ea9 Steffen Eiden 2026-04-02  86  		     "Failed to stop migration mode");
d487a24041c2ea9 Steffen Eiden 2026-04-02  87  
d487a24041c2ea9 Steffen Eiden 2026-04-02  88  	return 0;
d487a24041c2ea9 Steffen Eiden 2026-04-02  89  }
d487a24041c2ea9 Steffen Eiden 2026-04-02  90  

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