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List:       kvm
Subject:    Re: [PATCH] arch: x86: kvm: mmu.c: use true/false for bool type
From:       Paolo Bonzini <pbonzini () redhat ! com>
Date:       2019-10-31 10:13:04
Message-ID: 4af9e3b9-36f4-217f-c25c-3f4d64c0dde7 () redhat ! com
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On 31/10/19 07:57, SAURAV GIREPUNJE wrote:
> On Tue, Oct 29, 2019 at 04:44:23PM +0100, Peter Zijlstra wrote:
> > On Tue, Oct 29, 2019 at 07:12:46PM +0530, SAURAV GIREPUNJE wrote:
> > > On Tue, Oct 29, 2019 at 11:13:00AM +0100, Peter Zijlstra wrote:
> > > > On Tue, Oct 29, 2019 at 03:11:04PM +0530, Saurav Girepunje wrote:
> > > > > Use true/false for bool type "dbg" in mmu.c
> > > > > 
> > > > > Signed-off-by: Saurav Girepunje <saurav.girepunje@gmail.com>
> > > > > ---
> > > > > arch/x86/kvm/mmu.c | 2 +-
> > > > > 1 file changed, 1 insertion(+), 1 deletion(-)
> > > > > 
> > > > > diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
> > > > > index 24c23c66b226..c0b1df69ce0f 100644
> > > > > --- a/arch/x86/kvm/mmu.c
> > > > > +++ b/arch/x86/kvm/mmu.c
> > > > > @@ -68,7 +68,7 @@ enum {
> > > > > #undef MMU_DEBUG
> > > > > 
> > > > > #ifdef MMU_DEBUG
> > > > > -static bool dbg = 0;
> > > > > +static bool dbg = true;
> > > > 
> > > > You're actually changing the value from false to true. Please, if you
> > > > don't know C, don't touch things.
> > > Hi,
> > > 
> > > Thanks for your review.
> > > I accept that I have given wrong value "true" to debug variable. It's my bad my \
> > > typo mistake.   I will make sure that I will not touch your exclusive C code \
> > > where we can assign 0/1 to a bool variable, As you have given me a free advice, \
> > > I also request you to please don't review such small patches from newbie to \
> > > discourage them.
> > 
> > I will most certainly review whatever I want, and clearly it is needed.
> Do you want me to discard this patch or resend ?
> 

Hi Saurav,

In general I would be happy with replacing 0/1 with false/true, but not
in this particular case.  Despite working on KVM for quite some time I
have never found MMU_DEBUG particularly useful, therefore it is going to
go away soon and will be replaced with kernel tracepoints; see for
example commit 335e192a3fa4 ("KVM: x86: add tracepoints around
__direct_map and FNAME(fetch)", 2019-07-05).  Therefore, even such a
simple change would be very short lived.

Regarding this patch, I for one am happy that Peter caught the problem
in your patch.  His message was perhaps blunt but also honest;
contributing to the kernel requires a very good discipline.  I don't
want to discourage you from contributing, but I suggest that you look
into how you developed the patch (from the idea down to sending it) and
figure out how your mistake managed to slip.

Thanks,

Paolo


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