[bug report] KVM: PPC: Book3S HV: Outline of KVM-HV HPT resizing implementation

[Dan Carpenter <dan.carpenter@oracle.com>]

Hello David Gibson,

The patch 5e9859699aba: "KVM: PPC: Book3S HV: Outline of KVM-HV HPT
resizing implementation" from Dec 20, 2016, leads to the following
static checker warning:

	arch/powerpc/kvm/book3s_64_mmu_hv.c:1554 kvm_vm_ioctl_resize_hpt_commit()
	error: we previously assumed 'resize' could be null (see line 1532)

arch/powerpc/kvm/book3s_64_mmu_hv.c
  1514          mutex_lock(&kvm->lock);
  1515  
  1516          resize = kvm->arch.resize_hpt;
  1517  
  1518          /* This shouldn't be possible */
  1519          ret = -EIO;
  1520          if (WARN_ON(!kvm->arch.hpte_setup_done))
  1521                  goto out_no_hpt;
  1522  
  1523          /* Stop VCPUs from running while we mess with the HPT */
  1524          kvm->arch.hpte_setup_done = 0;
  1525          smp_mb();
  1526  
  1527          /* Boot all CPUs out of the guest so they re-read
  1528           * hpte_setup_done */
  1529          on_each_cpu(resize_hpt_boot_vcpu, NULL, 1);
  1530  
  1531          ret = -ENXIO;
  1532          if (!resize || (resize->order != shift))
                     ^^^^^^
Check.

  1533                  goto out;
  1534  
  1535          ret = -EBUSY;
  1536          if (!resize->prepare_done)
  1537                  goto out;
  1538  
  1539          ret = resize->error;
  1540          if (ret != 0)
  1541                  goto out;
  1542  
  1543          ret = resize_hpt_rehash(resize);
  1544          if (ret != 0)
  1545                  goto out;
  1546  
  1547          resize_hpt_pivot(resize);
  1548  
  1549  out:
  1550          /* Let VCPUs run again */
  1551          kvm->arch.hpte_setup_done = 1;
  1552          smp_mb();
  1553  out_no_hpt:
  1554          resize_hpt_release(kvm, resize);
                                        ^^^^^^
Oops.

  1555          mutex_unlock(&kvm->lock);
  1556          return ret;
  1557  }

regards,
dan carpenter