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SubjectRe: [PATCH 10/27] KVM: MMU: Add infrastructure for two-level page walker
On Mon, Sep 06, 2010 at 02:05:35PM -0400, Avi Kivity wrote:
> On 09/06/2010 06:55 PM, Joerg Roedel wrote:
> > This patch introduces a mmu-callback to translate gpa
> > addresses in the walk_addr code. This is later used to
> > translate l2_gpa addresses into l1_gpa addresses.
>
> > @@ -534,6 +534,11 @@ static inline gpa_t gfn_to_gpa(gfn_t gfn)
> > return (gpa_t)gfn<< PAGE_SHIFT;
> > }
> >
> > +static inline gfn_t gpa_to_gfn(gpa_t gpa)
> > +{
> > + return (gfn_t)gpa>> PAGE_SHIFT;
> > +}
> > +
>
> That's a bug - gfn_t may be smaller than gpa_t, so you're truncating
> just before the shift. Note the casts in the surrounding functions are
> widening, not narrowing.
>
> However, gfn_t is u64 so the bug is only theoretical.

Will fix that in v4 too. Thanks.

Joerg

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