Messages in this thread | | | Date | Mon, 22 Apr 2013 22:45:53 +0900 | From | Takuya Yoshikawa <> | Subject | Re: [PATCH v3 00/15] KVM: MMU: fast zap all shadow pages |
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On Mon, 22 Apr 2013 15:39:38 +0300 Gleb Natapov <gleb@redhat.com> wrote:
> > > Do not want kvm_set_memory (cases: DELETE/MOVE/CREATES) to be > > > suspectible to: > > > > > > vcpu 1 | kvm_set_memory > > > create shadow page > > > nuke shadow page > > > create shadow page > > > nuke shadow page > > > > > > Which is guest triggerable behavior with spinlock preemption algorithm. > > > > Not only guest triggerable as in the sense of a malicious guest, > > but condition above can be induced by host workload with non-malicious > > guest system. > > > Is the problem that newly created shadow pages are immediately zapped? > Shouldn't generation number/kvm_mmu_zap_all_invalid() idea described here > https://lkml.org/lkml/2013/4/22/111 solve this?
I guess so. That's what Avi described when he tried to achieve lockless TLB flushes. Mixing that idea with Xiao's approach will achieve reasonably nice performance, I think.
Various improvements should be added later on top of that if needed.
> > Also kvm_set_memory being relatively fast with huge memory guests > > is nice (which is what Xiaos idea allows).
I agree with this point. But if so, it should be actually measured on such guests, even if the algorithm looks promising.
Takuya
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