Re: [PATCH] KVM: x86: Fix function address when kvm_x86_ops.func is NULL

[Like Xu]

On 22/2/2022 4:33 pm, Paolo Bonzini wrote:
> On 2/22/22 07:25, Like Xu wrote:
> > From: Like Xu <likexu@xxxxxxxxxxx>
> >
> > Fix the function address for __static_call_return0() which is used by
> > static_call_update() when a func in struct kvm_x86_ops is NULL.
> >
> > Fixes: 5be2226f417d ("KVM: x86: allow defining return-0 static calls")
> > Signed-off-by: Like Xu <likexu@xxxxxxxxxxx>
>
> Sorry for the stupid question, but what breaks?

Although they are numerically the same, I suppose we should use the
& operator here, as in the other cases where __static_call_return0 is used.

What's more, Clang complains about the KVM_X86_OP_OPTIONAL_RET0 change:

./arch/x86/include/asm/kvm-x86-ops.h:108:1: warning: pointer type mismatch \
	('bool (*)(struct kvm_vcpu *)' (aka '_Bool (*)(struct kvm_vcpu *)') and 'void *') \
	[-Wpointer-type-mismatch]
and more warnings from [-Wpointer-type-mismatch]

Does it help you ?

> Paolo
>
> > ---
> >   arch/x86/include/asm/kvm_host.h | 2 +-
> >   1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> > index 713e08f62385..312f5ee19514 100644
> > --- a/arch/x86/include/asm/kvm_host.h
> > +++ b/arch/x86/include/asm/kvm_host.h
> > @@ -1548,7 +1548,7 @@ static inline void kvm_ops_static_call_update(void)
> >   #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);
> > +               (void *)&__static_call_return0);
> >   #include <asm/kvm-x86-ops.h>
> >   #undef __KVM_X86_OP
> >   }