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SubjectRe: [PATCH 2/2] KVM: X86: Implement PV send IPI support
On Fri, 29 Jun 2018 at 18:45, Paolo Bonzini <pbonzini@redhat.com> wrote:
>
> On 29/06/2018 11:51, Wanpeng Li wrote:
> > From: Wanpeng Li <wanpengli@tencent.com>
> >
> > Using hypercall to send IPIs by one vmexit instead of one by one for
> > xAPIC/x2APIC physical mode and one vmexit per-cluster for x2APIC cluster
> > mode.
> >
> > Even if enable qemu interrupt remapping and PV TLB Shootdown, I can still
> > observe ~14% performance boost by ebizzy benchmark for 64 vCPUs VM, the
> > total msr-induced vmexits reduce ~70%.
> >
> > Cc: Paolo Bonzini <pbonzini@redhat.com>
> > Cc: Radim Krčmář <rkrcmar@redhat.com>
> > Cc: Vitaly Kuznetsov <vkuznets@redhat.com>
> > Signed-off-by: Wanpeng Li <wanpengli@tencent.com>
> > ---
> > Documentation/virtual/kvm/cpuid.txt | 4 ++++
> > arch/x86/kvm/cpuid.c | 3 ++-
> > arch/x86/kvm/x86.c | 25 +++++++++++++++++++++++++
> > include/uapi/linux/kvm_para.h | 1 +
> > 4 files changed, 32 insertions(+), 1 deletion(-)
> >
> > diff --git a/Documentation/virtual/kvm/cpuid.txt b/Documentation/virtual/kvm/cpuid.txt
> > index ab022dc..d72359f 100644
> > --- a/Documentation/virtual/kvm/cpuid.txt
> > +++ b/Documentation/virtual/kvm/cpuid.txt
> > @@ -62,6 +62,10 @@ KVM_FEATURE_ASYNC_PF_VMEXIT || 10 || paravirtualized async PF VM exit
> > || || can be enabled by setting bit 2
> > || || when writing to msr 0x4b564d02
> > ------------------------------------------------------------------------------
> > +KVM_FEATURE_PV_SEND_IPI || 11 || guest checks this feature bit
> > + || || before enabling paravirtualized
> > + || || send IPIs.
>
> It's not "enabling" but "using". You also need to document the
> hypercall itself.

Will fix it in v2.

Regards,
Wanpeng Li

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