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    Subject[PATCH v2 0/5] KVM: VMX: Tscdeadline timer emulation fastpath
    Date
    IPI and Timer cause the main vmexits in cloud environment observation, 
    after single target IPI fastpath, let's optimize tscdeadline timer
    latency by introducing tscdeadline timer emulation fastpath, it will
    skip various KVM related checks when possible. i.e. after vmexit due
    to tscdeadline timer emulation, handle it and vmentry immediately
    without checking various kvm stuff when possible.

    Testing on SKX Server.

    cyclictest in guest(w/o mwait exposed, adaptive advance lapic timer is default -1):

    5632.75ns -> 4559.25ns, 19%

    kvm-unit-test/vmexit.flat:

    w/o APICv, w/o advance timer:
    tscdeadline_immed: 4780.75 -> 3851 19.4%
    tscdeadline: 7474 -> 6528.5 12.7%

    w/o APICv, w/ adaptive advance timer default -1:
    tscdeadline_immed: 4845.75 -> 3930.5 18.9%
    tscdeadline: 6048 -> 5871.75 3%

    w/ APICv, w/o avanced timer:
    tscdeadline_immed: 2919 -> 2467.75 15.5%
    tscdeadline: 5661.75 -> 5188.25 8.4%

    w/ APICv, w/ adaptive advance timer default -1:
    tscdeadline_immed: 3018.5 -> 2561 15.2%
    tscdeadline: 4663.75 -> 4537 2.7%

    Tested-by: Haiwei Li <lihaiwei@tencent.com>
    Cc: Haiwei Li <lihaiwei@tencent.com>

    v1 -> v2:
    * move more stuff from vmx.c to lapic.c
    * remove redundant checking
    * check more conditions to bail out CONT_RUN
    * not break AMD
    * not handle LVTT sepecial
    * cleanup codes

    Wanpeng Li (5):
    KVM: LAPIC: Introduce interrupt delivery fastpath
    KVM: X86: Introduce need_cancel_enter_guest helper
    KVM: VMX: Introduce generic fastpath handler
    KVM: X86: TSCDEADLINE MSR emulation fastpath
    KVM: VMX: Handle preemption timer fastpath

    arch/x86/include/asm/kvm_host.h | 2 +
    arch/x86/kvm/lapic.c | 98 +++++++++++++++++++++++++++++++++++++++--
    arch/x86/kvm/lapic.h | 2 +
    arch/x86/kvm/svm/avic.c | 5 +++
    arch/x86/kvm/svm/svm.c | 1 +
    arch/x86/kvm/svm/svm.h | 1 +
    arch/x86/kvm/vmx/vmx.c | 69 ++++++++++++++++++++++++-----
    arch/x86/kvm/x86.c | 42 ++++++++++++++----
    arch/x86/kvm/x86.h | 1 +
    9 files changed, 199 insertions(+), 22 deletions(-)

    --
    2.7.4

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