Re: [PATCH 4/8] i386: hvf: Implement CPU kick

[Roman Bolshakov]

On Mon, Jun 29, 2020 at 03:03:20PM +0200, Paolo Bonzini wrote:
> On 29/06/20 13:31, Roman Bolshakov wrote:
> > I implemented what you proposed using VMX-preemption timer in Pin-based
> > controls and regular hv_vcpu_run(). It works fine without noticable
> > regressions, I'll send that in v2.
> > 
> > hv_vcpu_run_until() was also evaluated on macOS 10.15.5 but it degrades
> > VM performance significantly compared to explicit setting of
> > VMX-preepmtion timer value and hv_vcpu_run(). The performance issue was
> > observed on Broadwell-based MacBook Air and Ivy Bridge-based MacBook
> > Pro.
> > 
> > macOS 11.0 Beta deprecated hv_vcpu_run() and introduced a special
> > declaration for hv_vcpu_run_until(), that's not available 10.15 -
> > HV_DEADLINE_FOREVER (UINT64_MAX, which is bigger than maximum value of
> > VMX-preeemption counter). Perhaps the performance issue is addressed
> > there.
> 
> Possibly.  I'm worried that the preemption-timer trick will fail to run
> there, but we'll see.
> 

Well, I've got new VM-exits (caused by zero preemption timer) on either
of my laptops.

-Roman