linux-kernel - Re: [PATCH v2] kvm: x86: mmu: Add cast to negated bitmasks in update_permission

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Date:   Mon, 25 Jun 2018 15:05:22 -0400
From:   Nick Desaulniers <ndesaulniers@...gle.com>
To:     joe@...ches.com
Cc:     Matthias Kaehlcke <mka@...omium.org>, pbonzini@...hat.com,
        rkrcmar@...hat.com, Thomas Gleixner <tglx@...utronix.de>,
        hpa@...or.com, x86@...nel.org, kvm@...r.kernel.org,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] kvm: x86: mmu: Add cast to negated bitmasks in update_permission_bitmask()

On Mon, Jun 25, 2018 at 1:50 PM Joe Perches <joe@...ches.com> wrote:
>
> On Mon, 2018-06-25 at 10:35 -0700, Matthias Kaehlcke wrote:
> > Some other instances of the warning that have been addressed are:
> > commit 644d87dccdc69cf79834a72ed0c889580d6af32a
> > commit e2a5dca753d1cdc3212519023ed8a13e13f5495b
> > commit dae1a432ab1fe79ae53129ededeaece35a2dc14d
> > commit d1600401faad4bc186bfdb291d8af644465e20bd
> > commit a45463cbf3f9dcdae683033c256f50bded513d6a
>
> I think all these implicit conversion warnings are senseless
> and should really be silenced by setting them only to be
> output at W=3 with all the other non-static and generally
> unnecessary signed/unsigned conversions
>
> ---
>  scripts/Makefile.extrawarn | 1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/scripts/Makefile.extrawarn b/scripts/Makefile.extrawarn
> index 8d5357053f86..9b1d0d59e8d0 100644
> --- a/scripts/Makefile.extrawarn
> +++ b/scripts/Makefile.extrawarn
> @@ -46,6 +46,7 @@ warning-2 += $(call cc-option, -Wunused-macros)
>  warning-3 := -Wbad-function-cast
>  warning-3 += -Wcast-qual
>  warning-3 += -Wconversion
> +warning-3 += $(call cc-option -Wconstant-conversion)
>  warning-3 += -Wpacked
>  warning-3 += -Wpadded
>  warning-3 += -Wpointer-arith

I prefer that to turning off the warning outright.

-- 
Thanks,
~Nick Desaulniers