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[PATCH 8/9] KVM: Adjust seven checks for null pointers

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  [PATCH 8/9] KVM: Adjust seven checks for null pointers SF Markus Elfring <elfring@users.sourceforge.net> - 2017-01-22 19:20 +0100
    Re: [PATCH 8/9] KVM: Adjust seven checks for null pointers kbuild test robot <lkp@intel.com> - 2017-01-22 22:30 +0100
    Re: [PATCH 8/9] KVM: Adjust seven checks for null pointers Dan Carpenter <dan.carpenter@oracle.com> - 2017-01-23 10:40 +0100

#1564489 — [PATCH 8/9] KVM: Adjust seven checks for null pointers

From: Markus Elfring <elfring@users.sourceforge.net>
Date: Sun, 22 Jan 2017 18:54:22 +0100
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

The script "checkpatch.pl" pointed information out like the following.

Comparison to NULL could be written …

Thus fix affected source code places.

Signed-off-by: Markus Elfring <elfring@users.sourceforge.net>
---
 virt/kvm/kvm_main.c | 17 ++++++++---------
 1 file changed, 8 insertions(+), 9 deletions(-)

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index ca88f3620ee3..4267a2c6f2aa 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -184,7 +184,7 @@ bool kvm_make_all_cpus_request(struct kvm *kvm, unsigned int req)
 		/* Set ->requests bit before we read ->mode. */
 		smp_mb__after_atomic();
 
-		if (cpus != NULL && cpu != -1 && cpu != me &&
+		if (cpus && cpu != -1 && cpu != me &&
 		      kvm_vcpu_exiting_guest_mode(vcpu) != OUTSIDE_GUEST_MODE)
 			cpumask_set_cpu(cpu, cpus);
 	}
@@ -1532,10 +1532,9 @@ static kvm_pfn_t hva_to_pfn(unsigned long addr, bool atomic, bool *async,
 
 retry:
 	vma = find_vma_intersection(current->mm, addr, addr + 1);
-
-	if (vma == NULL)
+	if (!vma) {
 		pfn = KVM_PFN_ERR_FAULT;
-	else if (vma->vm_flags & (VM_IO | VM_PFNMAP)) {
+	} else if (vma->vm_flags & (VM_IO | VM_PFNMAP)) {
 		r = hva_to_pfn_remapped(vma, addr, async, write_fault, &pfn);
 		if (r == -EAGAIN)
 			goto retry;
@@ -2835,7 +2834,7 @@ int kvm_register_device_ops(struct kvm_device_ops *ops, u32 type)
 	if (type >= ARRAY_SIZE(kvm_device_ops_table))
 		return -ENOSPC;
 
-	if (kvm_device_ops_table[type] != NULL)
+	if (kvm_device_ops_table[type])
 		return -EEXIST;
 
 	kvm_device_ops_table[type] = ops;
@@ -2844,7 +2843,7 @@ int kvm_register_device_ops(struct kvm_device_ops *ops, u32 type)
 
 void kvm_unregister_device_ops(u32 type)
 {
-	if (kvm_device_ops_table[type] != NULL)
+	if (kvm_device_ops_table[type])
 		kvm_device_ops_table[type] = NULL;
 }
 
@@ -2860,7 +2859,7 @@ static int kvm_ioctl_create_device(struct kvm *kvm,
 		return -ENODEV;
 
 	ops = kvm_device_ops_table[cd->type];
-	if (ops == NULL)
+	if (!ops)
 		return -ENODEV;
 
 	if (test)
@@ -3392,7 +3391,7 @@ static int kvm_io_bus_get_first_dev(struct kvm_io_bus *bus,
 
 	range = bsearch(&key, bus->range, bus->dev_count,
 			sizeof(struct kvm_io_range), kvm_io_bus_sort_cmp);
-	if (range == NULL)
+	if (!range)
 		return -ENOENT;
 
 	off = range - bus->range;
@@ -3803,7 +3802,7 @@ static int kvm_init_debug(void)
 	struct kvm_stats_debugfs_item *p;
 
 	kvm_debugfs_dir = debugfs_create_dir("kvm", NULL);
-	if (kvm_debugfs_dir == NULL)
+	if (!kvm_debugfs_dir)
 		goto out;
 
 	kvm_debugfs_num_entries = 0;
-- 
2.11.0

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#1564570

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Hi Markus,

[auto build test ERROR on kvm/linux-next]
[also build test ERROR on v4.10-rc4 next-20170120]
[if your patch is applied to the wrong git tree, please drop us a note to help improve the system]

url:    https://github.com/0day-ci/linux/commits/SF-Markus-Elfring/KVM-Fine-tuning-for-several-function-implementations/20170123-022323
base:   https://git.kernel.org/pub/scm/virt/kvm/kvm.git linux-next
config: mips-malta_kvm_defconfig (attached as .config)
compiler: mipsel-linux-gnu-gcc (Debian 6.1.1-9) 6.1.1 20160705
reproduce:
        wget https://git.kernel.org/cgit/linux/kernel/git/wfg/lkp-tests.git/plain/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # save the attached .config to linux build tree
        make.cross ARCH=mips 

All errors (new ones prefixed by >>):

   arch/mips/kvm/../../../virt/kvm/kvm_main.c: In function 'kvm_make_all_cpus_request':
>> arch/mips/kvm/../../../virt/kvm/kvm_main.c:187:7: error: the address of 'cpus' will always evaluate as 'true' [-Werror=address]
      if (cpus && cpu != -1 && cpu != me &&
          ^~~~
   cc1: all warnings being treated as errors

vim +187 arch/mips/kvm/../../../virt/kvm/kvm_main.c

   171	{
   172		int i, cpu, me;
   173		cpumask_var_t cpus;
   174		bool called = true;
   175		struct kvm_vcpu *vcpu;
   176	
   177		zalloc_cpumask_var(&cpus, GFP_ATOMIC);
   178	
   179		me = get_cpu();
   180		kvm_for_each_vcpu(i, vcpu, kvm) {
   181			kvm_make_request(req, vcpu);
   182			cpu = vcpu->cpu;
   183	
   184			/* Set ->requests bit before we read ->mode. */
   185			smp_mb__after_atomic();
   186	
 > 187			if (cpus && cpu != -1 && cpu != me &&
   188			      kvm_vcpu_exiting_guest_mode(vcpu) != OUTSIDE_GUEST_MODE)
   189				cpumask_set_cpu(cpu, cpus);
   190		}
   191		if (unlikely(cpus == NULL))
   192			smp_call_function_many(cpu_online_mask, ack_flush, NULL, 1);
   193		else if (!cpumask_empty(cpus))
   194			smp_call_function_many(cpus, ack_flush, NULL, 1);
   195		else

---
0-DAY kernel test infrastructure                Open Source Technology Center
https://lists.01.org/pipermail/kbuild-all                   Intel Corporation

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#1564818

Hm...  GCC complains about "if (array)" but not about
"if (array != NULL) ".  I view this as a bug in GCC...

But you should still be seeing these compile warnings.  This is
something like the 6th warning that kbuild has had to send you.

regards,
dan carpenter

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