linux-kernel - Re: [PATCH v4 6/7] mtrr, x86: Clean up mtrr_type

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Date:	Thu, 07 May 2015 07:45:04 -0600
From:	Toshi Kani <toshi.kani@...com>
To:	Borislav Petkov <bp@...en8.de>
Cc:	akpm@...ux-foundation.org, hpa@...or.com, tglx@...utronix.de,
	mingo@...hat.com, linux-mm@...ck.org, x86@...nel.org,
	linux-kernel@...r.kernel.org, dave.hansen@...el.com,
	Elliott@...com, pebolle@...cali.nl
Subject: Re: [PATCH v4 6/7] mtrr, x86: Clean up mtrr_type_lookup()

On Thu, 2015-05-07 at 09:52 +0200, Borislav Petkov wrote:
> On Wed, May 06, 2015 at 05:42:10PM -0600, Toshi Kani wrote:
> > Well, creating mtrr_type_lookup_fixed() is one of the comments I had in
> > the previous code review.  Anyway, let me make sure if I understand your
> > comment correctly.  Do the following changes look right to you?
> > 
> > 1) Change the caller responsible for the condition checks.
> > 
> >         if ((start < 0x100000) &&
> >             (mtrr_state.have_fixed) &&
> >             (mtrr_state.enabled & MTRR_STATE_MTRR_FIXED_ENABLED))
> >                 return mtrr_type_lookup_fixed(start, end);
> > 
> > 2) Delete the checks with mtrr_state in mtrr_type_lookup_fixed() as they
> > are done by the caller.  Keep the check with '(start >= 0x100000)' to
> > assure that the code handles the range [0xC0000 - 0xFFFFF] correctly.
> 
> That is a good defensive measure.
> 
> > static u8 mtrr_type_lookup_fixed(u64 start, u64 end)
> > {
> >         int idx;
> > 
> >         if (start >= 0x100000)
> >                  return MTRR_TYPE_INVALID;
> >  
> > -       if (!(mtrr_state.have_fixed) ||
> > -           !(mtrr_state.enabled & MTRR_STATE_MTRR_FIXED_ENABLED))
> > -               return MTRR_TYPE_INVALID;
> 
> Yeah, that's what I mean.

Thanks for the clarification! Will change accordingly.
-Toshi

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