Re: [Qemu-devel] [PATCH v5 1/3] target-i386: fallback vcpu's TSC rate to value returned by KVM

[Eduardo Habkost]

On Tue, Nov 17, 2015 at 01:20:37PM +0800, Haozhong Zhang wrote:
> If no user-specified TSC rate is present, we will try to set
> env->tsc_khz to the value returned by KVM_GET_TSC_KHZ.
> 
> Signed-off-by: Haozhong Zhang <address@hidden>
> ---
>  target-i386/kvm.c | 12 ++++++++++++
>  1 file changed, 12 insertions(+)
> 
> diff --git a/target-i386/kvm.c b/target-i386/kvm.c
> index 2a9953b..9e4d27f 100644
> --- a/target-i386/kvm.c
> +++ b/target-i386/kvm.c
> @@ -832,6 +832,18 @@ int kvm_arch_init_vcpu(CPUState *cs)
>          }
>      }
>  
> +    /*
> +     * If no user-specified TSC frequency is present, we will try to
> +     * set env->tsc_khz to the value used by KVM.
> +     */

If you send a new version of this series, please to describe
"why", not "what". We can see in the code that we are setting
env->tsc to the value used by KVM, but the comment need to
explain why.

> +    if (!env->tsc_khz) {
> +        r = kvm_check_extension(cs->kvm_state, KVM_CAP_GET_TSC_KHZ) ?
> +            kvm_vcpu_ioctl(cs, KVM_GET_TSC_KHZ) : -ENOTSUP;
> +        if (r > 0) {
> +            env->tsc_khz = r;
> +        }
> +    }
> +
>      if (has_xsave) {
>          env->kvm_xsave_buf = qemu_memalign(4096, sizeof(struct kvm_xsave));
>      }
> -- 
> 2.4.8
> 

-- 
Eduardo