Re: [BUG] [5.15] Compilation error in arch/x86/kvm/mmu/spte.h with clang-14

[Jim Mattson]

On Mon, Oct 4, 2021 at 9:13 AM Nick Desaulniers <ndesaulniers@xxxxxxxxxx> wrote:
>
> On Mon, Oct 4, 2021 at 2:49 AM Paolo Bonzini <pbonzini@xxxxxxxxxx> wrote:
> >
> > On 04/10/21 11:30, torvic9@xxxxxxxxxxx wrote:
> > >
> > >> Paolo Bonzini <pbonzini@xxxxxxxxxx> hat am 04.10.2021 11:26 geschrieben:
> > >>
> > >>
> > >> On 04/10/21 11:08, torvic9@xxxxxxxxxxx wrote:
> > >>> I encounter the following issue when compiling 5.15-rc4 with clang-14:
> > >>>
> > >>> In file included from arch/x86/kvm/mmu/mmu.c:27:
> > >>> arch/x86/kvm/mmu/spte.h:318:9: error: use of bitwise '|' with boolean operands [-Werror,-Wbitwise-instead-of-logical]
> > >>>           return __is_bad_mt_xwr(rsvd_check, spte) |
> > >>>                  ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > >>>                                                    ||
> > >>> arch/x86/kvm/mmu/spte.h:318:9: note: cast one or both operands to int to silence this warning
> > >>
> > >> The warning is wrong, as mentioned in the line right above:

Casting the bool to an int doesn't seem that onerous.

> > > So it's an issue with clang-14 then?
> > > (I add Nick and Nathan)
> >
> > My clang here doesn't have the option, so I'm going to ask---are you
> > using W=1?  I can see why clang is warning for KVM's code, but in my
> > opinion such a check should only be in -Wextra.
>
> This is a newly added warning in top of tree clang.
>
> >
> > Paolo
> >
> > >>
> > >>           /*
> > >>            * Use a bitwise-OR instead of a logical-OR to aggregate the reserved
> > >>            * bits and EPT's invalid memtype/XWR checks to avoid an extra Jcc
> > >>            * (this is extremely unlikely to be short-circuited as true).
> > >>            */
> > >>
> > >> Paolo
> > >
> >
>
>
> --
> Thanks,
> ~Nick Desaulniers