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

From: Paolo Bonzini
Date: Tue Jun 18 2013 - 10:27:13 EST


Il 07/06/2013 10:51, Xiao Guangrong ha scritto:
> Changelog:
> V3:
> All of these changes are from Gleb's review:
> 1) rename RET_MMIO_PF_EMU to RET_MMIO_PF_EMULATE.
> 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
>
> Xiao Guangrong (6):
> KVM: MMU: retain more available bits on mmio spte
> KVM: MMU: store generation-number into mmio spte
> KVM: MMU: make return value of mmio page fault handler more readable
> KVM: MMU: fast invalidate all mmio sptes
> KVM: MMU: add tracepoint for check_mmio_spte
> KVM: MMU: init kvm generation close to mmio wrap-around value
>
> arch/x86/include/asm/kvm_host.h | 2 +-
> arch/x86/kvm/mmu.c | 131 ++++++++++++++++++++++++++++++++--------
> arch/x86/kvm/mmu.h | 17 ++++++
> arch/x86/kvm/mmutrace.h | 34 +++++++++--
> arch/x86/kvm/paging_tmpl.h | 10 ++-
> arch/x86/kvm/vmx.c | 12 ++--
> arch/x86/kvm/x86.c | 11 +++-
> 7 files changed, 177 insertions(+), 40 deletions(-)
>

Xiao, is it time to add more comments to the code or update
Documentation/virtual/kvm/mmu.txt? Don't worry about the English, it is
more than understandable and I can help with the editing.

Paolo
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