Re: [PATCH v2] xen/p2m: Fix p2m_flush_table for non-nested cases

[Tamas Lengyel <tamas.lengyel@zentific.com>]

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On Wed, Feb 8, 2017 at 11:12 AM, George Dunlap <george.dunlap@citrix.com>
wrote:

> On 08/02/17 17:29, Tim Deegan wrote:
> > At 17:22 +0000 on 08 Feb (1486574546), George Dunlap wrote:
> >> Commit 71bb7304e7a7a35ea6df4b0cedebc35028e4c159 added flushing of
> >> nested p2m tables whenever the host p2m table changed.  Unfortunately
> >> in the process, it added a filter to p2m_flush_table() function so
> >> that the p2m would only be flushed if it was being used as a nested
> >> p2m.  This meant that the p2m was not being flushed at all for altp2m
> >> callers.
> >>
> >> Only check np2m_base if p2m_class is set to p2m_nested.
> >>
> >> NB that this is not a security issue: The only time this codepath is
> >> called is in cases where either nestedp2m or altp2m is enabled, and
> >> neither of them are in security support.
> >>
> >> Reported-by: Matt Leinhos <matt@starlab.io>
> >> Signed-off-by: George Dunlap <george.dunlap@citrix.com>
> >> CC: Tamas K Lengyel <tamas.lengyel@zentific.com>
> >> ---
> >>  xen/arch/x86/mm/p2m.c | 4 +++-
> >>  1 file changed, 3 insertions(+), 1 deletion(-)
> >>
> >> diff --git a/xen/arch/x86/mm/p2m.c b/xen/arch/x86/mm/p2m.c
> >> index 6548e9f..0af2ec1 100644
> >> --- a/xen/arch/x86/mm/p2m.c
> >> +++ b/xen/arch/x86/mm/p2m.c
> >> @@ -1627,7 +1627,9 @@ p2m_flush_table(struct p2m_domain *p2m)
> >>      ASSERT(page_list_empty(&p2m->pod.super));
> >>      ASSERT(page_list_empty(&p2m->pod.single));
> >>
> >> -    if ( p2m->np2m_base == P2M_BASE_EADDR )
> >> +    /* No need to flush if it's already empty */
> >> +    if ( p2m->p2m_class == p2m_nested &&
> >> +         p2m->np2m_base == P2M_BASE_EADDR )
> >
> > Looks like p2m_is_nestedp2m(p2m) is the usual idiom.  Either way:
> >
> > Reviewed-by: Tim Deegan <tim@xen.org>
>
> Right -- I'll change it to the usual idiom and check it in after I've
> gotten a test report (or waited a reasonable amount of time).


Tested-by: Tamas K Lengyel <tamas@tklengyel.com>

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