Re: [PATCH v2 08/10] KVM: x86: Add nested context management

[kernel test robot <lkp@intel.com>]

Hi,

kernel test robot noticed the following build warnings:

[auto build test WARNING on kvm/queue]
[also build test WARNING on kvm/next mst-vhost/linux-next linus/master v6.18-rc6 next-20251120]
[cannot apply to kvm/linux-next]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/griffoul-gmail-com/KVM-nVMX-Implement-cache-for-L1-MSR-bitmap/20251119-012332
base:   https://git.kernel.org/pub/scm/virt/kvm/kvm.git queue
patch link:    https://lore.kernel.org/r/20251118171113.363528-9-griffoul%40gmail.org
patch subject: [PATCH v2 08/10] KVM: x86: Add nested context management
config: i386-randconfig-141-20251120 (https://download.01.org/0day-ci/archive/20251121/202511210515.8L9NBb1R-lkp@intel.com/config)
compiler: clang version 20.1.8 (https://github.com/llvm/llvm-project 87f0227cb60147a26a1eeb4fb06e3b505e9c7261)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20251121/202511210515.8L9NBb1R-lkp@intel.com/reproduce)

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 <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202511210515.8L9NBb1R-lkp@intel.com/

All warnings (new ones prefixed by >>):

>> arch/x86/kvm/nested.c:133:10: warning: expression which evaluates to zero treated as a null pointer constant of type 'struct kvm_nested_context *' [-Wnon-literal-null-conversion]
     133 |                 return false;
         |                        ^~~~~
   1 warning generated.


vim +133 arch/x86/kvm/nested.c

   122	
   123	struct kvm_nested_context *kvm_nested_context_load(struct kvm_vcpu *vcpu,
   124							   gpa_t gpa)
   125	{
   126		struct kvm_nested_context_table *table;
   127		struct kvm_nested_context *ctx, *new_ctx = NULL;
   128		struct kvm *vm = vcpu->kvm;
   129		bool reset = false;
   130	
   131		table = vcpu->kvm->arch.nested_context_table;
   132		if (WARN_ON_ONCE(!table))
 > 133			return false;
   134	retry:
   135		spin_lock(&table->lock);
   136		ctx = kvm_nested_context_find(table, vcpu, gpa);
   137		if (!ctx) {
   138			/* At capacity? Recycle the LRU context */
   139			if (table->count >= kvm_nested_context_max(vcpu->kvm)) {
   140				ctx = kvm_nested_context_recycle(table);
   141				if (unlikely(!ctx))
   142					goto finish;
   143	
   144				kvm_nested_context_insert(table, ctx, gpa);
   145				++vm->stat.nested_context_recycle;
   146				reset = true;
   147	
   148			} else if (new_ctx) {
   149				++table->count;
   150				ctx = new_ctx;
   151				kvm_nested_context_insert(table, ctx, gpa);
   152				new_ctx = NULL;
   153	
   154			} else {
   155				/* Allocate a new context without holding the lock */
   156				spin_unlock(&table->lock);
   157				new_ctx = kvm_x86_ops.nested_ops->alloc_context(vcpu);
   158				if (unlikely(!new_ctx))
   159					return NULL;
   160	
   161				goto retry;
   162			}
   163		} else
   164			++vm->stat.nested_context_reuse;
   165	
   166		ctx->vcpu = vcpu;
   167	finish:
   168		spin_unlock(&table->lock);
   169	
   170		if (new_ctx)
   171			kvm_x86_ops.nested_ops->free_context(new_ctx);
   172	
   173		if (reset)
   174			kvm_x86_ops.nested_ops->reset_context(ctx);
   175	
   176		return ctx;
   177	}
   178	

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