Re: [Xen-devel] [PATCH] nestedhvm: fix write access fault on ro mapping

[Tim Deegan <tim@xxxxxxx>]

At 14:32 +0200 on 02 Aug (1343917962), Christoph Egger wrote:
> > It must be _possible_; after all we managed to detect the error. :)  In
> > any case it's definitely wrong to carry on with this handler with the
> > wrong address in hand.  So I wonder why this patch actually works for
> > you.  Does replacing the 'break' above with 'return 1' also fix the
> > problem?
> 
> No. Two things have to happen:
> 
> 1. Calling paging_mark_dirty() and
> 2. using the same p2mt from the hostp2m in the nestedp2m.
> 
> >
> 
> > In the short term, do you only care about pages that are read-only for
> > log-dirty tracking?  For the L1 walk, that should be handled by the PT
> > walker's own calls to paging_mark_dirty(), and the nested-p2m handler
> > could potentially take care of the other case by calling
> > paging_mark_dirty() (for writes!) before calling nestedhap_walk_L0_p2m().
> 
> Ok, I consider this as a performance improvement rather a bugfix.
> 
> New version is attached.

Applied, thanks.

Tim.

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