Re: [Xen-devel] [PATCH 1/3] xen: arm: avoid reusing incorrect mappings when walking the p2m.

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Mon, 2014-07-14 at 19:17 +0100, Julien Grall wrote:
> Hi Ian,
> 
> On 07/14/2014 05:27 PM, Ian Campbell wrote:
> > If we handle a change in a superpage then we need to invalidate any cached
> > mappings further down, otherwise we risk using them because their offset 
> > might
> > match but be based on a different offset further up the table.
> > 
> > Signed-off-by: Ian Campbell <ian.campbell@xxxxxxxxxx>
> > ---
> >  xen/arch/arm/p2m.c |    4 ++++
> >  1 file changed, 4 insertions(+)
> > 
> > diff --git a/xen/arch/arm/p2m.c b/xen/arch/arm/p2m.c
> > index c0c011a..917baa3 100644
> > --- a/xen/arch/arm/p2m.c
> > +++ b/xen/arch/arm/p2m.c
> > @@ -719,6 +719,8 @@ static int apply_p2m_changes(struct domain *d,
> >                  goto out;
> >              }
> >              cur_first_page = p2m_first_level_index(addr);
> > +            /* Any mapping further down is now invalid */
> > +            cur_second_offset = ~0;
> 
> I think you miss to invalid cur_first_offset.

I think you are right.

> Also, I think we have the same issue on Xen 4.4.

I'll add it to my list to check. I suspect the fix will need
reimplementing there rather than backporting.

Ian.



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