On 10/04/2010 05:56 PM, Gleb Natapov wrote:
When page is swapped in it is mapped into guest memory only after guest
tries to access it again and generate another fault. To save this fault
we can map it immediately since we know that guest is going to access
the page. Do it only when tdp is enabled for now. Shadow paging case is
more complicated. CR[034] and EFER registers should be switched before
doing mapping and then switched back.
With non-pv apf, I don't think we can do shadow paging. The guest isn't
aware of the apf, so as far as it is concerned it is allowed to kill the
process and replace it with something else:
guest process x: apf
kvm: timer intr
guest kernel: context switch
very fast guest admin: pkill -9 x
guest kernel: destroy x's cr3
guest kernel: reuse x's cr3 for new process y
kvm: retry fault, instantiating x's page in y's page table
Even with tdp, we have the same case for nnpt (just s/kernel/hypervisor/
and s/process/guest/). What we really need is to only instantiate the
page for direct maps, which are independent of the guest.
Could be done like this:
- at apf time, walk shadow mmu
- if !sp->role.direct, abort
- take reference to sp
- on apf completion, instantiate spte in sp
--
I have a truly marvellous patch that fixes the bug which this
signature is too narrow to contain.
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