Re: [PATCH v2 4/9] i386: hvf: Implement CPU kick

[Roman Bolshakov]

On Tue, Jun 30, 2020 at 02:33:42PM +0200, Paolo Bonzini wrote:
> On 30/06/20 12:28, Roman Bolshakov wrote:
> > @@ -966,6 +964,20 @@ int hvf_vcpu_exec(CPUState *cpu)
> >      return ret;
> >  }
> >  
> > +void hvf_vcpu_kick(CPUState *cpu)
> > +{
> > +    X86CPU *x86_cpu = X86_CPU(cpu);
> > +    CPUX86State *env = &x86_cpu->env;
> > +    hv_return_t err;
> > +
> > +    atomic_set(&env->hvf_deadline, 0);
> > +    err = hv_vcpu_interrupt(&cpu->hvf_fd, 1);
> > +    if (err) {
> > +        fprintf(stderr, "qemu:%s error %#x\n", __func__, err);
> > +        exit(1);
> > +    }
> 
> Can a signal interrupt hv_vcpu_run?  If so you actually don't need
> hv_vcpu_interrupt at all.

Existing signal masking and SIG_IPI didn't work IIRC when I tried to add
a primitive version of gdbstub support.

> You can also require the preemption time, all
> processor that support HVF have it, but never set it by default.  The
> deadline can be left at 0 all the time; instead, you toggle the bit in
> the pin-based controls.  In the signal handler you do:
> 
>       if (atomic_xchg(&env->hvf_in_guest, false)) {
>               wvmcs(cpu->hvf_fd, VMCS_PIN_BASED_CTLS,
>                     rvmcs(cpu->hvf_fd, VMCS_PIN_BASED_CTLS)
>                       | VMCS_PIN_BASED_CTLS_VMX_PREEMPT_TIMER);
>       }
> 
> In the main loop you do:
> 
>       atomic_set(&env->hvf_guest_mode, true);
>       smp_mb();
>       hv_vcpu_run(...);
>       atomic_set(&env->hvf_guest_mode, false);
> 
> and in the preemption timer vmexit handler:
>       
>               wvmcs(cpu->hvf_fd, VMCS_PIN_BASED_CTLS,
>                     rvmcs(cpu->hvf_fd, VMCS_PIN_BASED_CTLS)
>                       & ~VMCS_PIN_BASED_CTLS_VMX_PREEMPT_TIMER);
> 

Ok, I'll look into that. Thanks for the advices!

-Roman