Re: [Xen-devel] [PATCH] xen/p2m: Remove np2m-specific filter from generic p2m_flush_table

[Tim Deegan <tim@xxxxxxx>]

At 03:44 -0700 on 31 Jan (1485834259), Jan Beulich wrote:
> >>> On 30.01.17 at 16:17, <george.dunlap@xxxxxxxxxx> wrote:
> > Commit 71bb7304e7a7a35ea6df4b0cedebc35028e4c159 added flushing of
> > nested p2m tables whenever the host p2m table changed.  Unfortunately
> > in the process, it added a filter to the generic 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.
> > 
> > Instead do the nested p2m filtering in p2m_flush_nestedp2m().

I think it would be better to fix the test in p2m_flush_table() so it
understands altp2m's use of tables.  That way we won't have to deal
with filtering at other call sites, as Jan points out.  Also, this:

> >      for ( i = 0; i < MAX_NESTEDP2M; i++ )
> > -        p2m_flush_table(d->arch.nested_p2m[i]);
> > +    {
> > +        struct p2m_domain *p2m = d->arch.nested_p2m[i];
> > +        if ( p2m->np2m_base != P2M_BASE_EADDR )
> > +            p2m_flush_table(p2m);
> > +    }

moves the check of np2m_base outside the lock.  That might be OK but
it's definitely a bit subtle.

Cheers,

Tim.

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
https://lists.xen.org/xen-devel