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

[Tamas Lengyel <tamas.lengyel@xxxxxxxxxxxx>]

On Wed, Sep 26, 2018 at 10:49 AM George Dunlap <george.dunlap@xxxxxxxxxx> 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>

The mem_access/monitor bits are fairly trivial:

Acked-by: Tamas K Lengyel <tamas@xxxxxxxxxxxxx>

> ---
> NB, this is compile-tested only.

Are you planning to do some actual testing? I would highly recommend
that we see real test results before this is merged to verify
functionality.

Thanks,
Tamas

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