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

[Paolo Bonzini]

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.  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);

I'll leave out this patch in the meanwhile.

Paolo

> +}
> +
>  bool hvf_allowed;
>  
>  static int hvf_accel_init(MachineState *ms)
> diff --git a/target/i386/hvf/vmcs.h b/target/i386/hvf/vmcs.h
> index 42de7ebc3a..6615365023 100644
> --- a/target/i386/hvf/vmcs.h
> +++ b/target/i386/hvf/vmcs.h
> @@ -349,6 +349,7 @@
>  #define VMCS_PIN_BASED_CTLS_EXTINT            (1 << 0)
>  #define VMCS_PIN_BASED_CTLS_NMI               (1 << 3)
>  #define VMCS_PIN_BASED_CTLS_VNMI              (1 << 5)
> +#define VMCS_PIN_BASED_CTLS_VMX_PREEMPT_TIMER (1 << 6)
>  
>  #define VMCS_PRI_PROC_BASED_CTLS_INT_WINDOW_EXITING (1 << 2)
>  #define VMCS_PRI_PROC_BASED_CTLS_TSC_OFFSET (1 << 3)
>