Re: [PATCH 14/16] target/i386/hvf: Lock BQL outside of the vCPU inner execution loop

[Paolo Bonzini <pbonzini@redhat.com>]

On 8/13/26 20:16, Philippe Mathieu-Daudé wrote:
> Reduce lock contention by acquiring / releasing the BQL
> outside of the entire vCPU inner loop.
> 
> Signed-off-by: Philippe Mathieu-Daudé <philmd@oss.qualcomm.com>
> ---
>   target/i386/hvf/hvf.c | 19 +++++++++++--------
>   1 file changed, 11 insertions(+), 8 deletions(-)
> 
> diff --git a/target/i386/hvf/hvf.c b/target/i386/hvf/hvf.c
> index 0ffa3658dc5..f8bc01d38d3 100644
> --- a/target/i386/hvf/hvf.c
> +++ b/target/i386/hvf/hvf.c
> @@ -1009,6 +1009,9 @@ int hvf_arch_vcpu_exec(CPUState *cpu)
>           return EXCP_HLT;
>       }
>   
> +    bql_unlock();
> +    cpu_exec_start(cpu);
> +
>       /* Inner vCPU loop */
>       do {
>           if (cpu->vcpu_dirty) {
> @@ -1017,26 +1020,26 @@ int hvf_arch_vcpu_exec(CPUState *cpu)
>           }
>   
>           if (hvf_inject_interrupts(cpu)) {

Nope, hvf_inject_interrupts() calls cpu_get_pic_interrupt() which needs 
the BQL.

Paolo

> -            return EXCP_INTERRUPT;
> +            ret = EXCP_INTERRUPT;
> +            break;
>           }
> +
>           vmx_update_tpr(cpu);
>   
> -        bql_unlock();
>           if (!cpu_is_bsp(X86_CPU(cpu)) && cpu->halted) {

This is also incorrect by the way - chceking cpu->halted needs the BQL. 
So bql_unlock() must be moved right before cpu_exec_start().  Can you 
fix it?

Thanks,

Paolo

> -            bql_lock();
> -            return EXCP_HLT;
> +            ret = EXCP_HLT;
> +            break;
>           }
>   
> -        cpu_exec_start(cpu);
> -
>           hv_return_t r = hv_vcpu_run_until(cpu->accel->fd, HV_DEADLINE_FOREVER);
>           assert_hvf_ok(r);
>   
> -        cpu_exec_end(cpu);
> -
>           ret = hvf_handle_vmexit(cpu);
>       } while (ret == 0);
>   
> +    cpu_exec_end(cpu);
> +    bql_lock();
> +
>       return ret;
>   }
>