On Fri, Apr 24, 2020 at 7:46 AM Sean Christopherson <sean.j.christopherson@xxxxxxxxx> wrote: > > On Fri, Apr 24, 2020 at 12:01:43PM +0200, Peter Zijlstra wrote: > > On Fri, Apr 24, 2020 at 01:08:55PM +0800, Li RongQing wrote: > This requires four RDMSRs per VMX transition. Doing that unconditionally > will drastically impact performance. Not to mention that reading the MSRs > without checking for host support will generate #GPs and WARNs on hardware > without APERFMPERF. > > Assuming we're going forward with this, at an absolute minimum the RDMSRs > need to be wrapped with checks on host _and_ guest support for the emulated > behavior. Given the significant overhead, this might even be something > that should require an extra opt-in from userspace to enable. I would like to see performance data before enabling this unconditionally.
