linux-kernel - [RFC 0/9] KVM:x86/mmu:Introduce parallel memory virtualization to boost performance

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Date:   Wed,  5 Aug 2020 22:12:02 +0800
From:   Yulei Zhang <yulei.kernel@...il.com>
To:     pbonzini@...hat.com
Cc:     kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        sean.j.christopherson@...el.com, jmattson@...gle.com,
        vkuznets@...hat.com, xiaoguangrong.eric@...il.com,
        kernellwp@...il.com, lihaiwei.kernel@...il.com,
        Yulei Zhang <yuleixzhang@...cent.com>
Subject: [RFC 0/9] KVM:x86/mmu:Introduce parallel memory virtualization to boost performance

From: Yulei Zhang <yuleixzhang@...cent.com>

Currently in KVM memory virtulization we relay on mmu_lock to synchronize
the memory mapping update, which make vCPUs work in serialize mode and
slow down the execution, especially after migration to do substantial
memory mapping setup, and performance get worse if increase vCPU numbers
and guest memories.

The idea we present in this patch set is to mitigate the issue with
pre-constructed memory mapping table. We will fast pin the guest memory
to build up a global memory mapping table according to the guest memslots
changes and apply it to cr3, so that after guest starts up all the vCPUs
would be able to update the memory concurrently, thus the performance 
improvement is expected.

And after test the initial patch with memory dirty pattern workload, we
have seen positive results even with huge page enabled. For example,
guest with 32 vCPUs and 64G memories, in 2M/1G huge page mode we would get
more than 50% improvement. 

Yulei Zhang (9):
  Introduce new fields in kvm_arch/vcpu_arch struct for direct build EPT
    support
  Introduce page table population function for direct build EPT feature
  Introduce page table remove function for direct build EPT feature
  Add release function for direct build ept when guest VM exit
  Modify the page fault path to meet the direct build EPT requirement
  Apply the direct build EPT according to the memory slots change
  Add migration support when using direct build EPT
  Introduce kvm module parameter global_tdp to turn on the direct build
    EPT mode
  Handle certain mmu exposed functions properly while turn on direct
    build EPT mode

 arch/mips/kvm/mips.c            |  13 +
 arch/powerpc/kvm/powerpc.c      |  13 +
 arch/s390/kvm/kvm-s390.c        |  13 +
 arch/x86/include/asm/kvm_host.h |  13 +-
 arch/x86/kvm/mmu/mmu.c          | 537 ++++++++++++++++++++++++++++++--
 arch/x86/kvm/svm/svm.c          |   2 +-
 arch/x86/kvm/vmx/vmx.c          |  17 +-
 arch/x86/kvm/x86.c              |  55 ++--
 include/linux/kvm_host.h        |   7 +-
 virt/kvm/kvm_main.c             |  43 ++-
 10 files changed, 648 insertions(+), 65 deletions(-)

-- 
2.17.1