RE: [RFC PATCH v6 6/6] KVM: selftests: Add tests for VM and vCPU cap KVM_CAP_X86_DISABLE_EXITS

Kechen Lu
2023-02-02T20:17:10Z

Hi Zhi,

> -----Original Message-----
> From: Zhi Wang <zhi.wang.linux@gmail.com>
> Sent: Thursday, February 2, 2023 7:09 AM
> To: Kechen Lu <kechenl@nvidia.com>
> Cc: kvm@vger.kernel.org; seanjc@google.com; pbonzini@redhat.com;
> chao.gao@intel.com; shaoqin.huang@intel.com; vkuznets@redhat.com;
> linux-kernel@vger.kernel.org
> Subject: Re: [RFC PATCH v6 6/6] KVM: selftests: Add tests for VM and vCPU
> cap KVM_CAP_X86_DISABLE_EXITS
>
> External email: Use caution opening links or attachments
>
>
> On Sat, 21 Jan 2023 02:07:38 +0000
> Kechen Lu <kechenl@nvidia.com> wrote:
>
> It works on my box now. LGTM. I was curious if there is any other userspace
> application using this? It would be interesting to see their strategies.
>
Thanks for testing this! Appreciated.

For userspace applications, we had a POC with the changes in QEMU, to do the static per-vCPU HLT disabling, depending on the users to have the flexibility run guest workloads on these none-hlt-exits vCPUs instead of disabling hlt exits for whole VM, we saw 3%+ performance benefits. Furthermore, we had the dynamically toggled hlt exits strategy applied on QEMU, which depending on the guest stats and heuristics to do the hlt exits toggling.

BR,
Kechen