Re: [Xen-devel] [RFC PATCH 2/2] x86/mm: Add mem access rights to NPT

[Alexandru Stefan ISAILA <aisaila@xxxxxxxxxxxxxxx>]

On 26.09.2018 19:47, George Dunlap wrote:
> From: Isaila Alexandru <aisaila@xxxxxxxxxxxxxxx>
> 
> This patch adds access control for NPT mode.
> 
> There aren’t enough extra bits to store the access rights in the NPT p2m
> table, so we add a radix tree to store extra information.
> 
> For efficiency:
>   - Only allocate this radix tree when we first store "non-default"
>     extra information
> 
>   - Remove entires which match the default extra information rather
>     than continuing to store them
> 
>   - For superpages, only store an entry for the first gfn in the
>     superpage.  Use the order of the p2m entry being read to determine
>     the proper place to look in the radix table.
> 
> Modify p2m_type_to_flags() to accept and interpret an access value,
> parallel to the ept code.
> 
> Add a set_default_access() method to the p2m-pt and p2m-ept versions
> of the p2m rather than setting it directly, to deal with different
> default permitted access values.
> 
> Signed-off-by: Alexandru Isaila <aisaila@xxxxxxxxxxxxxxx>
> Signed-off-by: George Dunlap <george.dunlap@xxxxxxxxxx>
> ---
> NB, this is compile-tested only.
> 
> cc'ing Paul because this is functionality he may want at some point in
> the future.
> 
> I'm not sure why we only allow 'int' to be stored in the radix tree,
> but that throws away 30-some bits we could otherwise use.  We might
> consider revising this if we run out of bits here.
> 
> CC: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
> CC: Jan Beulich <jbeulich@xxxxxxxx>
> CC: Tim Deegan <tim@xxxxxxx>
> CC: Tamas K Lengyel <tamas.lengyel@xxxxxxxxxxxx>
> CC: Paul Durrant <paul.durrant@xxxxxxxxxx>
> CC: Razvan Cojocaru <rcojocaru@xxxxxxxxxxxxxxx>

Hi all,

I know it's been some time from the start of this patch but can this 
move forward? Any thoughts or acks are appreciated.

Thanks,
Alex
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