Re: [Xen-devel] [PATCH] xen: expose shadow_blow_tables to userspace

[Jean Guyader <jean.guyader@xxxxxxxxx>]

On 10 May 2012 11:37, Tim Deegan <tim@xxxxxxx> wrote:
> At 10:57 +0100 on 10 May (1336647456), Jean Guyader wrote:
>> Add a new xc function to destroy the shadow pages table for a given
>> guest from userspace.
>
> Looks OK, but what will it be used for?  There might be some more
> appropriate semantics at the hypercall interface than exposing the
> shadow internals as such.
>

It's related to the use of hvm_set_mem_pinned_cacheattr to set the default
caching policy when a guest starts to use a given gfn.

If this function is called after the guest has mapped the gfn it won't
have any affect.
The easy and surely not the best way to fix this is to destroy all the
shadow page
tables for this domain.

Maybe the ideal thing to do would be to make the cacheattr code aware
of the shadow page table and only clear the relevant set of shadow pages.

Jean

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