Re: [Xen-devel] [PATCH v2] x86/ept: pass correct level to p2m_entry_modify

["Tian, Kevin" <kevin.tian@xxxxxxxxx>]

> From: Roger Pau Monne [mailto:roger.pau@xxxxxxxxxx]
> Sent: Wednesday, July 3, 2019 7:33 PM
> 
> EPT differs from NPT and shadow when translating page orders to levels
> in the physmap page tables. EPT page tables level for order 0 pages is
> 0, while NPT and shadow instead use 1, ie: EPT page tables levels
> starts at 0 while NPT and shadow starts at 1.
> 
> Fix the p2m_entry_modify call in atomic_write_ept_entry to always add
> one to the level, in order to match NPT and shadow usage.
> 
> While there also add a check to ensure p2m_entry_modify is never
> called with level == 0. That should allow to catch future errors
> related to the level parameter.
> 
> Fixes: c7a4c088ad1c ('x86/mm: split p2m ioreq server pages special handling
> into helper')
> Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>

Reviewed-by: Kevin Tian <kevin.tian@xxxxxxxxx>
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