On Tue, Nov 24, 2015 at 11:33:56AM +0800, Haozhong Zhang wrote:
> Following changes are made to the TSC rate setting code in
> kvm_arch_init_vcpu():
> * The code is moved to a new function kvm_arch_set_tsc_khz().
> * If kvm_arch_set_tsc_khz() fails, i.e. following two conditions are
> both satisfied:
> * KVM does not support the TSC scaling or it fails to set vcpu's
> TSC rate by KVM_SET_TSC_KHZ,
> * the TSC rate to be set is different than the value currently used
> by KVM,
> then kvm_arch_init_vcpu() will fail. Prevously,
> * the lack of TSC scaling never failed kvm_arch_init_vcpu(),
> * the failure of KVM_SET_TSC_KHZ failed kvm_arch_init_vcpu()
> unconditionally, even though the TSC rate to be set is identical
> to the value currently used by KVM.
>
> Signed-off-by: Haozhong Zhang <haozhong.zhang@xxxxxxxxx>
Reviewed-by: Eduardo Habkost <ehabkost@xxxxxxxxxx>
> ---
> target-i386/kvm.c | 40 +++++++++++++++++++++++++++++++++-------
> 1 file changed, 33 insertions(+), 7 deletions(-)
>
> diff --git a/target-i386/kvm.c b/target-i386/kvm.c
> index a0fe9d4..1e811ee 100644
> --- a/target-i386/kvm.c
> +++ b/target-i386/kvm.c
> @@ -524,6 +524,36 @@ static bool hyperv_enabled(X86CPU *cpu)
> cpu->hyperv_runtime);
> }
>
> +static int kvm_arch_set_tsc_khz(CPUState *cs)
> +{
> + X86CPU *cpu = X86_CPU(cs);
> + CPUX86State *env = &cpu->env;
> + int r;
> +
> + if (!env->tsc_khz) {
> + return 0;
> + }
> +
> + r = kvm_check_extension(cs->kvm_state, KVM_CAP_TSC_CONTROL) ?
> + kvm_vcpu_ioctl(cs, KVM_SET_TSC_KHZ, env->tsc_khz) :
> + -ENOTSUP;
> + if (r < 0) {
> + /* When KVM_SET_TSC_KHZ fails, it's an error only if the current
> + * TSC frequency doesn't match the one we want.
> + */
> + int cur_freq = kvm_check_extension(cs->kvm_state, KVM_CAP_GET_TSC_KHZ) ?
> + kvm_vcpu_ioctl(cs, KVM_GET_TSC_KHZ) :
> + -ENOTSUP;
> + if (cur_freq <= 0 || cur_freq != env->tsc_khz) {
> + error_report("warning: TSC frequency mismatch between "
> + "VM and host, and TSC scaling unavailable");
> + return r;
> + }
> + }
> +
> + return 0;
> +}
> +
> static Error *invtsc_mig_blocker;
>
> #define KVM_MAX_CPUID_ENTRIES 100
> @@ -823,13 +853,9 @@ int kvm_arch_init_vcpu(CPUState *cs)
> return r;
> }
>
> - r = kvm_check_extension(cs->kvm_state, KVM_CAP_TSC_CONTROL);
> - if (r && env->tsc_khz) {
> - r = kvm_vcpu_ioctl(cs, KVM_SET_TSC_KHZ, env->tsc_khz);
> - if (r < 0) {
> - fprintf(stderr, "KVM_SET_TSC_KHZ failed\n");
> - return r;
> - }
> + r = kvm_arch_set_tsc_khz(cs);
> + if (r < 0) {
> + return r;
> }
>
> /* vcpu's TSC frequency is either specified by user, or following
> --
> 2.4.8
>
--
Eduardo
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