Hi Sean,
On Wed, Feb 23, 2022 at 04:23:55PM +0000, Sean Christopherson wrote:
> Cast kvm_x86_ops.func to 'void *' when updating KVM static calls that are
> conditionally patched to __static_call_return0(). clang complains about
> using mismatching pointers in the ternary operator, which breaks the
> build when compiling with CONFIG_KVM_WERROR=y.
>
> >> arch/x86/include/asm/kvm-x86-ops.h:82:1: warning: pointer type mismatch
> ('bool (*)(struct kvm_vcpu *)' and 'void *') [-Wpointer-type-mismatch]
>
> Fixes: 5be2226f417d ("KVM: x86: allow defining return-0 static calls")
> Reported-by: Like Xu <like.xu.linux@xxxxxxxxx>
> Reported-by: kernel test robot <lkp@xxxxxxxxx>
> Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
Thank you for the patch! Is this a bug in clang? I ended up creating a
small reproducer in case we need to file a bug with clang upstream:
https://godbolt.org/z/P7nEdzejE
This does shut up the warning and I can still spawn guests on my AMD and
Intel systems so:
Reviewed-by: Nathan Chancellor <nathan@xxxxxxxxxx>
Tested-by: Nathan Chancellor <nathan@xxxxxxxxxx>
> ---
> arch/x86/include/asm/kvm_host.h | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> index 713e08f62385..f285ddb8b66b 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -1547,8 +1547,8 @@ static inline void kvm_ops_static_call_update(void)
> WARN_ON(!kvm_x86_ops.func); __KVM_X86_OP(func)
> #define KVM_X86_OP_OPTIONAL __KVM_X86_OP
> #define KVM_X86_OP_OPTIONAL_RET0(func) \
> - static_call_update(kvm_x86_##func, kvm_x86_ops.func ? : \
> - (void *) __static_call_return0);
> + static_call_update(kvm_x86_##func, (void *)kvm_x86_ops.func ? : \
> + (void *)__static_call_return0);
> #include <asm/kvm-x86-ops.h>
> #undef __KVM_X86_OP
> }
>
> base-commit: f4bc051fc91ab9f1d5225d94e52d369ef58bec58
> --
> 2.35.1.473.g83b2b277ed-goog
>
