Re: [PATCH v4 2/7] mtrr, x86: Fix MTRR lookup to handle inclusive entry

Toshi Kani
2015-05-05T19:50:45Z

On Tue, 2015-05-05 at 20:39 +0200, Borislav Petkov wrote:
> On Tue, May 05, 2015 at 11:32:08AM -0600, Toshi Kani wrote:
> > > Ok, I'm confused. Shouldn't the inclusive:1 case be
> > >
> > > (start:mtrr_start) (mtrr_start:mtrr_end) (mtrr_end:end)
> > >
> > > ?
> > >
> > > If so, this function would need more changes...
> >
> > Yes, that's how it gets separated eventually. Since *repeat is set in
> > this case, the code only needs to separate the first part at a time.
> > The 2nd part gets separated in the next call with the *repeat.
>
> Aah, right, the caller is supposed to adjust the interval limits on
> subsequent calls. Please reflect this in the comment because:
>
> * (start:mtrr_start) (mtrr_start:end)
>
> is misleading for inclusive:1.

Well, the comment kinda says it already, but I will try to clarify it.

/*
* We have start:end spanning across an MTRR.
* We split the region into either
* - start_state:1
* (start:mtrr_end) (mtrr_end:end)
* - end_state:1 or inclusive:1
* (start:mtrr_start) (mtrr_start:end)
* depending on kind of overlap.
* Return the type for first region and a pointer to
* the start of second region so that caller will
* lookup again on the second region.
* Note: This way we handle multiple overlaps as well.
*/

Thanks,
-Toshi