linux-kernel - RE: [RFC PATCH v6 2/6] KVM: x86: Move *_in_guest power management flags to vCPU scope

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Date:   Thu, 2 Feb 2023 19:42:19 +0000
From:   Kechen Lu <kechenl@...dia.com>
To:     Zhi Wang <zhi.wang.linux@...il.com>,
        "seanjc@...gle.com" <seanjc@...gle.com>
CC:     "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "pbonzini@...hat.com" <pbonzini@...hat.com>,
        "chao.gao@...el.com" <chao.gao@...el.com>,
        "shaoqin.huang@...el.com" <shaoqin.huang@...el.com>,
        "vkuznets@...hat.com" <vkuznets@...hat.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [RFC PATCH v6 2/6] KVM: x86: Move *_in_guest power management
 flags to vCPU scope

Hi Zhi,

> -----Original Message-----
> From: Zhi Wang <zhi.wang.linux@...il.com>
> Sent: Thursday, February 2, 2023 6:57 AM
> To: Kechen Lu <kechenl@...dia.com>
> Cc: kvm@...r.kernel.org; seanjc@...gle.com; pbonzini@...hat.com;
> chao.gao@...el.com; shaoqin.huang@...el.com; vkuznets@...hat.com;
> linux-kernel@...r.kernel.org
> Subject: Re: [RFC PATCH v6 2/6] KVM: x86: Move *_in_guest power
> management flags to vCPU scope
> 
> External email: Use caution opening links or attachments
> 
> 
> On Sat, 21 Jan 2023 02:07:34 +0000
> Kechen Lu <kechenl@...dia.com> wrote:
> 
> > Make the runtime disabled mwait/hlt/pause/cstate exits flags vCPU
> > scope to allow finer-grained, per-vCPU control.  The VM-scoped control
> > is only allowed before vCPUs are created, thus preserving the existing
> > behavior is a simple matter of snapshotting the flags at vCPU creation.
> >
> > Signed-off-by: Kechen Lu <kechenl@...dia.com>
> > Suggested-by: Sean Christopherson <seanjc@...gle.com>
> > Reviewed-by: Sean Christopherson <seanjc@...gle.com>
> > ---
> >  arch/x86/include/asm/kvm_host.h |  5 +++++
> >  arch/x86/kvm/cpuid.c            |  4 ++--
> >  arch/x86/kvm/lapic.c            |  7 +++----
> >  arch/x86/kvm/svm/nested.c       |  4 ++--
> >  arch/x86/kvm/svm/svm.c          | 12 ++++++------
> >  arch/x86/kvm/vmx/vmx.c          | 16 ++++++++--------
> >  arch/x86/kvm/x86.c              |  6 +++++-
> >  arch/x86/kvm/x86.h              | 16 ++++++++--------
> >  8 files changed, 39 insertions(+), 31 deletions(-)
> >
> > diff --git a/arch/x86/include/asm/kvm_host.h
> > b/arch/x86/include/asm/kvm_host.h index 6aaae18f1854..41b998234a04
> > 100644
> > --- a/arch/x86/include/asm/kvm_host.h
> > +++ b/arch/x86/include/asm/kvm_host.h
> > @@ -1009,6 +1009,11 @@ struct kvm_vcpu_arch {  #if
> > IS_ENABLED(CONFIG_HYPERV)
> >       hpa_t hv_root_tdp;
> >  #endif
> > +
> > +     bool mwait_in_guest;
> > +     bool hlt_in_guest;
> > +     bool pause_in_guest;
> > +     bool cstate_in_guest;
> 
> Better add some comments here. When xxx_in_guest stays together with
> XXX_DISABLE_EXIT_XXX, it can be quite confusing. Or maybe align the
> naming like bool disable_exit_mwait <-> XXX_DISABLE_EXIT_XXX.
> 
This *_in_guest naming aligns with what current kvm_arch has, and exists for long time, not sure if there are still needs to add comments here. Would like to see Sean's options on this.

BR,
Kechen