Re: [Xen-devel] [PATCH v14 07/11] x86/mm: add an extra command to HYPERVISOR_mmu_update...

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 13.12.17 at 18:03, <Paul.Durrant@xxxxxxxxxx> wrote:
> Looking through the code, the only one thing that bothers me is the 
> page_set_owner() done in shadow_enable() for the page used for HVM guest 
> vcpus that have paging disabled. AFAICT that page would become mappable by an 
> emulating domain with MMU_PT_UPDATE_NO_TRANSLATE, if it figured out or 
> guessed the correct MFN, but I'm not sure whether damage could be done to Xen 
> using that.

I was afraid of a problem here too, but Tim did convince me that
there's no problem as this is a page table being shadowed, not a
page table the guest actually runs on. Corrupting the page's
contents would only affect the guest (just like is the case for any
other guest page tables).

Jan


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