Re: [kvmarm:fixes 18/18] arch/arm64/kvm/hyp/nvhe/mem_protect.c:1086:9: warning: variable 'ret' is uninitialized when used here

[Quentin Perret <qperret@google.com>]

On Monday 10 Feb 2025 at 09:21:29 (+0000), Marc Zyngier wrote:
> On Mon, 10 Feb 2025 01:39:04 +0000,
> kernel test robot <lkp@intel.com> wrote:
> > 
> > tree:   https://git.kernel.org/pub/scm/linux/kernel/git/kvmarm/kvmarm.git fixes
> > head:   eabc7aaef7a553b64bf6e631ce04526af6c8d104
> > commit: eabc7aaef7a553b64bf6e631ce04526af6c8d104 [18/18] KVM: arm64: Simplify np-guest hypercalls
> > config: arm64-allmodconfig (https://download.01.org/0day-ci/archive/20250210/202502100911.8c9DbtKD-lkp@intel.com/config)
> > compiler: clang version 18.1.8 (https://github.com/llvm/llvm-project 3b5b5c1ec4a3095ab096dd780e84d7ab81f3d7ff)
> > reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20250210/202502100911.8c9DbtKD-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/202502100911.8c9DbtKD-lkp@intel.com/
> > 
> > All warnings (new ones prefixed by >>):
> > 
> > >> arch/arm64/kvm/hyp/nvhe/mem_protect.c:1086:9: warning: variable 'ret' is uninitialized when used here [-Wuninitialized]
> >     1086 |         return ret;
> >          |                ^~~
> >    arch/arm64/kvm/hyp/nvhe/mem_protect.c:1076:9: note: initialize the variable 'ret' to silence this warning
> >     1076 |         int ret;
> >          |                ^
> >          |                 = 0
> >    1 warning generated.
> 
> Nice catch. I wish the compiler would warn for these by default...

So do I...

> Quentin, are you happy with the following patch that I can stash on
> top of the current set of fixes?

Absolutely, thanks for the patch and sorry the mess!

    Reviewed-by: Quentin Perret <qperret@google.com>

> From 5da62486aeda7d7d11107db8ed4e6421e3a2a364 Mon Sep 17 00:00:00 2001
> From: Marc Zyngier <maz@kernel.org>
> Date: Mon, 10 Feb 2025 09:17:58 +0000
> Subject: [PATCH] KVM: arm64: Fix __pkvm_host_mkyoung_guest() return value
> 
> Don't use an uninitialised stack variable, and just return 0
> on the non-error path.
> 
> Reported-by: kernel test robot <lkp@intel.com>
> Closes: https://lore.kernel.org/oe-kbuild-all/202502100911.8c9DbtKD-lkp@intel.com/
> Signed-off-by: Marc Zyngier <maz@kernel.org>
> ---
>  arch/arm64/kvm/hyp/nvhe/mem_protect.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/arch/arm64/kvm/hyp/nvhe/mem_protect.c b/arch/arm64/kvm/hyp/nvhe/mem_protect.c
> index 4c2f6a6a2efe1..19c3c631708ce 100644
> --- a/arch/arm64/kvm/hyp/nvhe/mem_protect.c
> +++ b/arch/arm64/kvm/hyp/nvhe/mem_protect.c
> @@ -1073,7 +1073,6 @@ int __pkvm_host_mkyoung_guest(u64 gfn, struct pkvm_hyp_vcpu *vcpu)
>  {
>  	struct pkvm_hyp_vm *vm = pkvm_hyp_vcpu_to_hyp_vm(vcpu);
>  	u64 ipa = hyp_pfn_to_phys(gfn);
> -	int ret;
>  
>  	if (pkvm_hyp_vm_is_protected(vm))
>  		return -EPERM;
> @@ -1083,5 +1082,5 @@ int __pkvm_host_mkyoung_guest(u64 gfn, struct pkvm_hyp_vcpu *vcpu)
>  	kvm_pgtable_stage2_mkyoung(&vm->pgt, ipa, 0);
>  	guest_unlock_component(vm);
>  
> -	return ret;
> +	return 0;
>  }
> -- 
> 2.39.2
> 
> 
> -- 
> Without deviation from the norm, progress is not possible.