On 05/02/2018 07:57, Wanpeng Li wrote: > From: Wanpeng Li <wanpengli@xxxxxxxxxxx> > > If host CPUs are dedicated to a VM, we can avoid VM exits on HLT. > This patch adds the per-VM non-HLT-exiting capability. > > Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx> > Cc: Radim Krčmář <rkrcmar@xxxxxxxxxx> > Signed-off-by: Wanpeng Li <wanpengli@xxxxxxxxxxx> > --- > v1 -> v2: > * vmx_clear_hlt() around INIT handling > * vmx_clear_hlt() upon SMI and implement auto halt restart Hi Wanpeng, sorry I could not answer before. We do not need to implement AutoHalt. It's a messy functionality and the way it works is much simpler: on RSM the microcode reads AutoHALT's bit 0 and... decrements RIP if it is 1. All you need to do however is clear the activity state. Guests should expect anyway that "CLI;HLT" can be interrupted by an NMI and follow it with a JMP. Second, I would prefer to implement at the same time MWAIT and PAUSE passthrough, as in https://www.spinics.net/lists/kvm/msg159517.html: > The three capabilities are more or less all doing the same thing. > Perhaps it would make some sense to only leave PAUSE spin loops in > guest, but not HLT/MWAIT; but apart from that I think users would > probably enable all of them. So I think we should put in the > documentation that blindly passing the KVM_CHECK_EXTENSION result to > KVM_ENABLE_CAP is a valid thing to do when vCPUs are associated to > dedicated physical CPUs. > > Let's get rid of KVM_CAP_X86_GUEST_MWAIT altogether and > add a new capability. But let's use just one. Thanks again for your work, and sorry for slightly contradicting Radim's review. I've rebased and applied patch 2. Paolo
