[kvm:dirty-ring-buffer 79/80] arch/x86/kvm/../../../virt/kvm/gfn_ring.c:122:9: sparse: context imbalance in 'kvm_gfn_ring_push' - different lock contexts for basic block

[kbuild test robot <fengguang.wu@xxxxxxxxx>]

tree:   https://git.kernel.org/pub/scm/virt/kvm/kvm.git dirty-ring-buffer
head:   8d19462882d3ad12238755956d9154f3732f78bf
commit: 9a13921dd3dcd4b653b6eaefd46668d7d7cf0b7c [79/80] KVM: Implement ring-based dirty memory tracking
reproduce:
        # apt-get install sparse
        git checkout 9a13921dd3dcd4b653b6eaefd46668d7d7cf0b7c
        make ARCH=x86_64 allmodconfig
        make C=1 CF=-D__CHECK_ENDIAN__


sparse warnings: (new ones prefixed by >>)


vim +/kvm_gfn_ring_push +122 arch/x86/kvm/../../../virt/kvm/gfn_ring.c

    88	
    89	int kvm_gfn_ring_push(struct kvm_gfn_ring *gfnring,
    90			      u32 slot,
    91			      u64 offset,
    92			      bool locked)
    93	{
    94		int ret;
    95		u16 num;
    96		struct kvm_dirty_gfn *entry;
    97	
    98		if (locked)
    99			spin_lock(&gfnring->lock);
   100	
   101		num = (u16)(gfnring->dirty_index - gfnring->reset_index);
   102		if (num >= gfnring->size) {
   103			WARN_ON_ONCE(num > gfnring->size);
   104			ret = -EBUSY;
   105			goto out;
   106		}
   107	
   108		entry = &gfnring->dirty_ring->dirty_gfns[gfnring->dirty_index &
   109				(gfnring->size - 1)];
   110		entry->slot = slot;
   111		entry->offset = offset;
   112		smp_wmb();
   113		gfnring->dirty_index++;
   114		num = gfnring->dirty_index - gfnring->reset_index;
   115		gfnring->dirty_ring->indices.avail_index = gfnring->dirty_index;
   116		ret = num >= gfnring->soft_limit;
   117	
   118	out:
   119		if (locked)
   120			spin_unlock(&gfnring->lock);
   121	
 > 122		return ret;
   123	}
   124	

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