On Thu, Mar 24, 2011 at 11:51:59AM +0200, Avi Kivity wrote:
> On 03/24/2011 09:40 AM, Joerg Roedel wrote:
>> This patch enhances the kvm_amd module with functions to
>> support the TSC_RATE_MSR which can be used to set a given
>> tsc frequency for the guest vcpu.
>>
>>
>> @@ -1141,6 +1175,9 @@ static void svm_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
>>
>> for (i = 0; i< NR_HOST_SAVE_USER_MSRS; i++)
>> rdmsrl(host_save_user_msrs[i], svm->host_user_msrs[i]);
>> +
>> + if (static_cpu_has(X86_FEATURE_TSCRATEMSR)&& svm->tsc_scale.enabled)
>> + wrmsrl(MSR_AMD64_TSC_RATIO, svm->tsc_scale.ratio);
>> }
>>
>> static void svm_vcpu_put(struct kvm_vcpu *vcpu)
>> @@ -1161,6 +1198,9 @@ static void svm_vcpu_put(struct kvm_vcpu *vcpu)
>> #endif
>> for (i = 0; i< NR_HOST_SAVE_USER_MSRS; i++)
>> wrmsrl(host_save_user_msrs[i], svm->host_user_msrs[i]);
>> +
>> + if (static_cpu_has(X86_FEATURE_TSCRATEMSR)&& svm->tsc_scale.enabled)
>> + wrmsr(MSR_AMD64_TSC_RATIO, 0, 1);
>> }
>
> This is a bit suboptimal. We could do something like
>
> static DEFINE_PER_CPU(u64, current_tsc_scale);
>
> static void svm_vcpu_load(...)
> {
> ...
> if (svm->tsc_scale != __get_cpu_var(current_tsc_scale)) {
> __get_cpu_var(current_tsc_scale) = svm->tsc_scale;
> wrmsrl(MSR_AMD64_TSC_RATIO, svm->tsc_scale);
> }
> }
>
> with no changes to svm_vcpu_put() (note no tsc_scale.enabled either,
> just put the unity value for disabled).
Right, this is a good optimization. Thanks for the hint, I'll change it.
Regards,
Joerg
--
To unsubscribe from this list: send the line "unsubscribe kvm" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
