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

[Paolo Bonzini]

On 30/06/20 17:50, Roman Bolshakov wrote:
> 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 try pthread_kill followed by hv_vcpu_interrupt if it doesn't.
The signal would be delivered after return to userspace.

Paolo

>> 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
>