2021-10-18 18:38:53

by Paolo Bonzini

Subject: [PATCH v2] KVM: x86: avoid warning with -Wbitwise-instead-of-logical

This is a new warning in clang top-of-tree (will be 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 code is fine, but change it anyway to shut up this clever clogs
of a compiler.

Reported-by: [email protected]
Signed-off-by: Paolo Bonzini <[email protected]>
---
arch/x86/kvm/mmu/spte.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kvm/mmu/spte.h b/arch/x86/kvm/mmu/spte.h
index 7c0b09461349..66782e796c0a 100644
--- a/arch/x86/kvm/mmu/spte.h
+++ b/arch/x86/kvm/mmu/spte.h
@@ -315,7 +315,7 @@ static __always_inline bool is_rsvd_spte(struct rsvd_bits_validate *rsvd_check,
* bits and EPT's invalid memtype/XWR checks to avoid an extra Jcc
* (this is extremely unlikely to be short-circuited as true).
*/
- return __is_bad_mt_xwr(rsvd_check, spte) |
+ return __is_bad_mt_xwr(rsvd_check, spte) ||
__is_rsvd_bits_set(rsvd_check, spte, level);
}

--
2.27.0

2021-10-18 18:44:08

by Jim Mattson

Subject: Re: [PATCH v2] KVM: x86: avoid warning with -Wbitwise-instead-of-logical

On Mon, Oct 18, 2021 at 11:36 AM Paolo Bonzini <[email protected]> wrote:
>
> This is a new warning in clang top-of-tree (will be 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 code is fine, but change it anyway to shut up this clever clogs
> of a compiler.
>
> Reported-by: [email protected]
> Signed-off-by: Paolo Bonzini <[email protected]>
> ---
> arch/x86/kvm/mmu/spte.h | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/x86/kvm/mmu/spte.h b/arch/x86/kvm/mmu/spte.h
> index 7c0b09461349..66782e796c0a 100644
> --- a/arch/x86/kvm/mmu/spte.h
> +++ b/arch/x86/kvm/mmu/spte.h
> @@ -315,7 +315,7 @@ static __always_inline bool is_rsvd_spte(struct rsvd_bits_validate *rsvd_check,
> * bits and EPT's invalid memtype/XWR checks to avoid an extra Jcc
> * (this is extremely unlikely to be short-circuited as true).
> */
> - return __is_bad_mt_xwr(rsvd_check, spte) |
> + return __is_bad_mt_xwr(rsvd_check, spte) ||
> __is_rsvd_bits_set(rsvd_check, spte, level);
> }
You should probably elide the comment above.

Reviewed-by: Jim Mattson <[email protected]>