> -----Original Message----- > From: Sean Christopherson <seanjc@xxxxxxxxxx> > Sent: Wednesday, March 15, 2023 8:16 AM > To: Li,Rongqing <lirongqing@xxxxxxxxx> > Cc: kvm@xxxxxxxxxxxxxxx; x86@xxxxxxxxxx; Paolo Bonzini > <pbonzini@xxxxxxxxxx>; Wanpeng Li <wanpengli@xxxxxxxxxxx>; Vitaly > Kuznetsov <vkuznets@xxxxxxxxxx> > Subject: Re: [PATCH] x86/kvm: refine condition for checking vCPU preempted > > +Paolo, Wanpeng, and Vitaly > > In the future, use get_maintainers.pl to build To: and Cc: so that the right folks > see the patch. Not everyone habitually scours the KVM list. :-) > Ok > On Wed, Feb 15, 2023, lirongqing@xxxxxxxxx wrote: > > From: Li RongQing <lirongqing@xxxxxxxxx> > > > > Check whether vcpu is preempted or not when HLT is trapped or there is > > not realtime hint. > > Please explain _why_ there's no need to check for preemption in this setup. > What may be obvious to you isn't necessarily obvious to reviewers or readers. > I will rewrite the changelog > > In other words, it is unnecessary to check preemption if HLT is not > > intercepted and guest has realtime hint > > > > Signed-off-by: Li RongQing <lirongqing@xxxxxxxxx> > > --- > > arch/x86/kernel/kvm.c | 6 ++++-- > > 1 file changed, 4 insertions(+), 2 deletions(-) > > > > diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c index > > 1cceac5..1a2744d 100644 > > --- a/arch/x86/kernel/kvm.c > > +++ b/arch/x86/kernel/kvm.c > > @@ -820,8 +820,10 @@ static void __init kvm_guest_init(void) > > has_steal_clock = 1; > > static_call_update(pv_steal_clock, kvm_steal_clock); > > > > - pv_ops.lock.vcpu_is_preempted = > > - PV_CALLEE_SAVE(__kvm_vcpu_is_preempted); > > + if (kvm_para_has_feature(KVM_FEATURE_PV_UNHALT) || > > Rather than have the guest rely on host KVM behavior clearing PV_UNHALT > when HLT is passed through), would it make sense to add something like > KVM_HINTS_HLT_PASSTHROUGH to more explicitly tell the guest that HLT isn't > intercepted? KVM_HINTS_HLT_PASSTHROUGH is more obvious, but it need both kvm and guest support Thanks -Li > > > + !kvm_para_has_hint(KVM_HINTS_REALTIME)) > > Misaligned indentation (one too many spaces). > > > + pv_ops.lock.vcpu_is_preempted = > > + PV_CALLEE_SAVE(__kvm_vcpu_is_preempted); > > } > > > > if (kvm_para_has_feature(KVM_FEATURE_PV_EOI)) > > -- > > 2.9.4 > >
