Re: [Xen-devel] changing attributes of a page!

[Tim Deegan <tim@xxxxxxx>]

Hi, 

Please don't top-post. 

At 14:41 +0330 on 09 Jan (1326120068), Mohamad Rezaei wrote:
> I have started Dom0 with dom0_shadow=1. So it must be running with a
> read-only page table. I thought p2m is responsible for updating the
> dom0's page-table.

PV guests don't have p2m in the hypervisor -- they take care of their
own p2m translations and make pagetables that already point to machihe
addresses.

> I have looked at _sh_propagate() but I couldn't
> find any option to change page attributes like RWX.

Look again. :)  That function makes the PTE that the hardware will
see.  So all you need to do is mask _PAGE_RW out of the sflags when you
see an l1 entry where target_mfn is one of the MFNs you're protecting.
Look at how log-dirty is handled, for example. 

Of course, once you've done that, you also need to handle the pagefaults
that will happen if the guest writes to that memory!

Tim.

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