Hi Marcelo, On 04/16/2013 08:54 AM, Marcelo Tosatti wrote: > On Mon, Apr 01, 2013 at 05:56:43PM +0800, Xiao Guangrong wrote: >> Changelog in v2: >> - rename kvm_mmu_invalid_mmio_spte to kvm_mmu_invalid_mmio_sptes >> - use kvm->memslots->generation as kvm global generation-number >> - fix comment and codestyle >> - init kvm generation close to mmio wrap-around value >> - keep kvm_mmu_zap_mmio_sptes >> >> The current way is holding hot mmu-lock and walking all shadow pages, this >> is not scale. This patchset tries to introduce a very simple and scale way >> to fast invalid all mmio sptes - it need not walk any shadow pages and hold >> any locks. >> >> The idea is simple: >> KVM maintains a global mmio invalid generation-number which is stored in >> kvm->memslots.generation and every mmio spte stores the current global >> generation-number into his available bits when it is created >> >> When KVM need zap all mmio sptes, it just simply increase the global >> generation-number. When guests do mmio access, KVM intercepts a MMIO #PF >> then it walks the shadow page table and get the mmio spte. If the >> generation-number on the spte does not equal the global generation-number, >> it will go to the normal #PF handler to update the mmio spte >> >> Since 19 bits are used to store generation-number on mmio spte, we zap all >> mmio sptes when the number is round > > Hi Xiao, > > Is it still necessary with generation numbers at 'struct shadow_page' > level (which covers the slot deletion case). Yes. > > That is, once kvm_mmu_zap_all is fixed to increase generation count and > nuke roots, can't that be used instead with similar effectiveness for > SLOT_CREATE/SLOT_MOVE cases? It seems not easy. :( We can not increase kvm's generation count for SLOT_CREATE since any change on kvm->generation_count will cause all vcpus fault on _all_ memory region. We also can not separately update mmio-sp's generation count instead of zapping them since a sp can have both mmio-spte and normal-spte, we should zap the normal spte on a mmio-sp. Thanks! -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
