> -----Original Message-----
> From: Sean Christopherson <seanjc@xxxxxxxxxx>
> Sent: Monday, January 10, 2022 11:36 AM
> To: Kechen Lu <kechenl@xxxxxxxxxx>
> Cc: kvm@xxxxxxxxxxxxxxx; pbonzini@xxxxxxxxxx; wanpengli@xxxxxxxxxxx;
> vkuznets@xxxxxxxxxx; mst@xxxxxxxxxx; Somdutta Roy
> <somduttar@xxxxxxxxxx>; linux-kernel@xxxxxxxxxxxxxxx
> Subject: Re: [RFC PATCH v2 2/3] KVM: x86: move ()_in_guest checking to
> vCPU scope
>
> External email: Use caution opening links or attachments
>
>
> The shortlog is weird, I get what you're going for with the "()", but it honestly
> looks like a typo :-) And add "power management" so that there's a bit more
> context in the shortlog? Maybe this?
>
> KVM: x86: Move *_in_guest power management flags to vCPU scope
>
Ack. Yeah it's a typo :)
> On Tue, Dec 21, 2021, Kechen Lu wrote:
> > For futher extensions on finer-grained control on per-vCPU exits
> > disable control, and because VM-scoped restricted to set before vCPUs
> > creation, runtime disabled exits flag check could be purely vCPU
> > scope.
>
> State what the patch does, not what it "could" do. E.g.
>
> 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.
>
Ack! Thanks for patient refinement on the description wording :P
> A few nits below that aren't even from this path, but otherwise,
>
> Reviewed-by: Sean Christopherson <seanjc@xxxxxxxxxx>
>
> > Suggested-by: Sean Christopherson <seanjc@xxxxxxxxxx>
> > Signed-off-by: Kechen Lu <kechenl@xxxxxxxxxx>
> > ---
> > arch/x86/include/asm/kvm_host.h | 5 +++++
> > arch/x86/kvm/cpuid.c | 2 +-
> > arch/x86/kvm/lapic.c | 2 +-
> > arch/x86/kvm/svm/svm.c | 10 +++++-----
> > arch/x86/kvm/vmx/vmx.c | 16 ++++++++--------
> > arch/x86/kvm/x86.c | 6 +++++-
> > arch/x86/kvm/x86.h | 16 ++++++++--------
> > 7 files changed, 33 insertions(+), 24 deletions(-)
> >
> > diff --git a/arch/x86/include/asm/kvm_host.h
> > b/arch/x86/include/asm/kvm_host.h index 2164b9f4c7b0..edc5fca4d8c8
> > 100644
> > --- a/arch/x86/include/asm/kvm_host.h
> > +++ b/arch/x86/include/asm/kvm_host.h
> > @@ -908,6 +908,11 @@ 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;
> > };
> >
> > struct kvm_lpage_info {
> > diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c index
> > 07e9215e911d..6291e15710ba 100644
> > --- a/arch/x86/kvm/cpuid.c
> > +++ b/arch/x86/kvm/cpuid.c
> > @@ -177,7 +177,7 @@ void kvm_update_cpuid_runtime(struct kvm_vcpu
> *vcpu)
> > best->ebx = xstate_required_size(vcpu->arch.xcr0, true);
> >
> > best = kvm_find_kvm_cpuid_features(vcpu);
> > - if (kvm_hlt_in_guest(vcpu->kvm) && best &&
> > + if (kvm_hlt_in_guest(vcpu) && best &&
> > (best->eax & (1 << KVM_FEATURE_PV_UNHALT)))
>
> Can you (or Paolo?) opportunistically align this? And maybe even shuffle the
> check on "best" to pair the !NULL check with the functional check? E.g.
>
> if (kvm_hlt_in_guest(vcpu) &&
> best && (best->eax & (1 << KVM_FEATURE_PV_UNHALT)))
> best->eax &= ~(1 << KVM_FEATURE_PV_UNHALT);
>
Makes sense. Let me align and reform this in this patch.
> > best->eax &= ~(1 << KVM_FEATURE_PV_UNHALT);
> >
> > diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c index
> > f206fc35deff..effb994e6642 100644
> > --- a/arch/x86/kvm/lapic.c
> > +++ b/arch/x86/kvm/lapic.c
> > @@ -119,7 +119,7 @@ static bool kvm_can_post_timer_interrupt(struct
> > kvm_vcpu *vcpu) bool kvm_can_use_hv_timer(struct kvm_vcpu *vcpu) {
> > return kvm_x86_ops.set_hv_timer
> > - && !(kvm_mwait_in_guest(vcpu->kvm) ||
> > + && !(kvm_mwait_in_guest(vcpu) ||
>
> And another opportunistic tweak? I'm been itching for an excuse to "fix" this
> particular helper for quite some time :-)
>
> return kvm_x86_ops.set_hv_timer &&
> !(kvm_mwait_in_guest(vcpu) ||
> kvm_can_post_timer_interrupt(vcpu));
>
> That overruns the 80 char soft limit, but IMO it's worth it in this case as the
> resulting code is more readable.
>
Sure!
Best Regards,
Kechen
>
> > kvm_can_post_timer_interrupt(vcpu));
> > }
> > EXPORT_SYMBOL_GPL(kvm_can_use_hv_timer);
