Re: [Xen-devel] [PATCH] p2m/ept: pass correct level to atomic_write_ept_entry in ept_invalidate_emt

[Roger Pau Monné <roger.pau@xxxxxxxxxx>]

On Fri, Aug 23, 2019 at 05:58:29AM +0000, Tian, Kevin wrote:
> > From: Roger Pau Monne [mailto:roger.pau@xxxxxxxxxx]
> > Sent: Tuesday, August 20, 2019 11:38 PM
> > 
> > The level passed to ept_invalidate_emt corresponds to the EPT entry
> > passed as the mfn parameter, which is a pointer to an EPT page table,
> > hence the entries in that page table will have one level less than the
> > parent.
> > 
> > Fix the call to atomic_write_ept_entry to pass the correct level, ie:
> > one level less than the parent.
> > 
> > Fixes: 50fe6e73705 ('pvh dom0: add and remove foreign pages')
> > Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
> > ---
> > Cc: Jun Nakajima <jun.nakajima@xxxxxxxxx>
> > Cc: Kevin Tian <kevin.tian@xxxxxxxxx>
> > Cc: George Dunlap <george.dunlap@xxxxxxxxxxxxx>
> > Cc: Jan Beulich <jbeulich@xxxxxxxx>
> > Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
> > Cc: Wei Liu <wl@xxxxxxx>
> > Cc: Sergey Dyasli <sergey.dyasli@xxxxxxxxxx>
> > Cc: Paul Durrant <paul.durrant@xxxxxxxxxx>
> > ---
> >  xen/arch/x86/mm/p2m-ept.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/xen/arch/x86/mm/p2m-ept.c b/xen/arch/x86/mm/p2m-ept.c
> > index 6b8468c793..23ae6e9da3 100644
> > --- a/xen/arch/x86/mm/p2m-ept.c
> > +++ b/xen/arch/x86/mm/p2m-ept.c
> > @@ -367,7 +367,7 @@ static bool_t ept_invalidate_emt(struct p2m_domain
> > *p2m, mfn_t mfn,
> >          e.emt = MTRR_NUM_TYPES;
> >          if ( recalc )
> >              e.recalc = 1;
> > -        rc = atomic_write_ept_entry(p2m, &epte[i], e, level);
> > +        rc = atomic_write_ept_entry(p2m, &epte[i], e, level - 1);
> >          ASSERT(rc == 0);
> >          changed = 1;
> >      }
> 
> Reviewed-by: Kevin Tian <kevin.tian@xxxxxxxxx>.
> 
> One small comment about readability. What about renaming 'level'
> to 'parent_level' in this function?

Sure, I guess this can be done while committing it, or else I can send
a follow up.

Thanks, Roger.

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