> -----Original Message----- > From: Sean Christopherson <seanjc@xxxxxxxxxx> > Sent: Wednesday, March 15, 2023 11:27 PM > 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 > > On Wed, Mar 15, 2023, Li,Rongqing wrote: > > > 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 > > Yeah, that's the downside. But modifying KVM and/or the userspace VMM > shouldn't be difficult, i.e the only meaningful cost is the rollout of a new > kernel/VMM. > > On the other hand, establishing the heuristic that !PV_UNHALT == > HLT_PASSTHROUGH could have to subtle issues in the future. It safe-ish in the > context of this patch as userspace is unlikely to set KVM_HINTS_REALTIME, hide > PV_UNHALT, and _not_ passthrough HLT. But without the REALTIME side of > things, !PV_UNHALT == HLT_PASSTHROUGH is much less likely to hold true. Ok, could you submit these codes Thanks -Li
