Re: [PATCH v6 1/3] target-i386: fallback vcpu's TSC rate to value returned by KVM

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On Tue, Nov 24, 2015 at 11:33:55AM +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. This patch does
> not change the current functionality of QEMU and just prepares for later
> patches to enable migrating vcpu's TSC rate.
> 
> Signed-off-by: Haozhong Zhang <haozhong.zhang@xxxxxxxxx>

Reviewed-by: Eduardo Habkost <ehabkost@xxxxxxxxxx>

> ---
>  target-i386/kvm.c | 14 ++++++++++++++
>  1 file changed, 14 insertions(+)
> 
> diff --git a/target-i386/kvm.c b/target-i386/kvm.c
> index 2a9953b..a0fe9d4 100644
> --- a/target-i386/kvm.c
> +++ b/target-i386/kvm.c
> @@ -832,6 +832,20 @@ int kvm_arch_init_vcpu(CPUState *cs)
>          }
>      }
>  
> +    /* vcpu's TSC frequency is either specified by user, or following
> +     * the value used by KVM if the former is not present. In the
> +     * latter case, we query it from KVM and record in env->tsc_khz,
> +     * so that vcpu's TSC frequency can be migrated later via this field.
> +     */
> +    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
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