linux-kernel - Re: [PATCH v2 3/5] KVM: x86: warn on incorrectly NULL static calls

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Date:   Tue, 15 Feb 2022 17:10:41 +0000
From:   Sean Christopherson <seanjc@...gle.com>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Subject: Re: [PATCH v2 3/5] KVM: x86: warn on incorrectly NULL static calls

For the shortlog, it's not the "static call" that's incorrectly NULL, it's the
kvm_x86_ops.func that's wrong.  E.g. yank out static calls and KVM could still
keep the WARN.

On Mon, Feb 14, 2022, Paolo Bonzini wrote:
> Use the newly corrected KVM_X86_OP annotations to warn about possible
> NULL pointer dereferences as soon as the vendor module is loaded.
> 
> Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
> ---
>  arch/x86/include/asm/kvm_host.h | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> index e3f7d958c150..5dce6fbd9ab6 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -1546,9 +1546,10 @@ extern struct kvm_x86_ops kvm_x86_ops;
>  
>  static inline void kvm_ops_static_call_update(void)
>  {
> -#define KVM_X86_OP(func) \
> +#define KVM_X86_OP_OPTIONAL(func) \
>  	static_call_update(kvm_x86_##func, kvm_x86_ops.func);
> -#define KVM_X86_OP_OPTIONAL KVM_X86_OP
> +#define KVM_X86_OP(func) \
> +	WARN_ON(!kvm_x86_ops.func); KVM_X86_OP_OPTIONAL(func)

As before, I'd prefer that we not have a KVM_X86_OP => KVM_X86_OP_OPTIONAL
dependency and instead have a common __KVM_X86_OP for this one case.

>  #include <asm/kvm-x86-ops.h>
>  }
>  
> -- 
> 2.31.1
> 
>