Re: [PATCH v3 0/6] KVM: MMU: fast invalidate all mmio sptes

From: Xiao Guangrong
Date: Mon Jun 10 2013 - 04:41:59 EST

On 06/10/2013 03:56 PM, Gleb Natapov wrote:
> On Fri, Jun 07, 2013 at 04:51:22PM +0800, Xiao Guangrong wrote:
>> Changelog:
>> V3:
>> All of these changes are from Gleb's review:
>> 2) smartly adjust kvm generation number in kvm_current_mmio_generatio()
>> to avoid kvm_memslots->generation overflow.
>> 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 invalidate all mmio sptes - it need not walk any shadow pages and hold
>> any locks.
>> The idea is simple:
>> KVM maintains a global mmio valid 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
> Looks good to me, but doesn't tis obsolete kvm_mmu_zap_mmio_sptes() and
> sp->mmio_cached, so they should be removed as part of the patch series?

Yes, i agree, they should be removed. :)

There is the patch to do these things: