Hi,
On Tue, Nov 17, 2015 at 01:20:39PM +0800, Haozhong Zhang wrote:
> This patch enables migrating vcpu's TSC rate. If KVM on the destination
> machine supports TSC scaling, guest programs will observe a consistent
> TSC rate across the migration.
>
> If TSC scaling is not supported on the destination machine, the
> migration will not be aborted and QEMU on the destination will not set
> vcpu's TSC rate to the migrated value.
>
> If vcpu's TSC rate specified by CPU option 'tsc-freq' on the destination
> machine is inconsistent with the migrated TSC rate, the migration will
> be aborted.
>
> For backwards compatibility, the migration of vcpu's TSC rate is
> disabled on pc-*-2.4 and older machine types.
>
> Signed-off-by: Haozhong Zhang <haozhong.zhang@xxxxxxxxx>
Now the logic in this patch (and the rest of the series) looks
good to me. All my suggestions are only related to code comments
and error handling:
[...]
> diff --git a/target-i386/kvm.c b/target-i386/kvm.c
> index 6a1acb4..6856899 100644
> --- a/target-i386/kvm.c
> +++ b/target-i386/kvm.c
> @@ -2384,6 +2384,10 @@ int kvm_arch_put_registers(CPUState *cpu, int level)
> }
> }
>
> + if (level == KVM_PUT_FULL_STATE) {
> + kvm_arch_set_tsc_khz(cpu);
Please add a comment here indicating that errors are being
ignored, and explaining why.
> + }
> +
> ret = kvm_getput_regs(x86_cpu, 1);
> if (ret < 0) {
> return ret;
> diff --git a/target-i386/machine.c b/target-i386/machine.c
> index a18e16e..3c5d24b 100644
> --- a/target-i386/machine.c
> +++ b/target-i386/machine.c
> @@ -331,6 +331,13 @@ static int cpu_post_load(void *opaque, int version_id)
> CPUX86State *env = &cpu->env;
> int i;
>
> + if (env->tsc_khz && env->user_tsc_khz &&
> + env->tsc_khz != env->user_tsc_khz) {
> + fprintf(stderr, "Mismatch between user-specified TSC frequency and "
> + "migrated TSC frequency\n");
Please use error_report() instead of fprintf().
> + return -1;
Please return a valid -errno value. Other post_load functions
that implement sanity checks use -EINVAL (e.g.
global_state_post_load(), configuration_post_load()), so that's
probably what we should do here.
> + }
> +
> /*
> * Real mode guest segments register DPL should be zero.
> * Older KVM version were setting it wrongly.
> @@ -775,6 +782,26 @@ static const VMStateDescription vmstate_xss = {
> }
> };
>
> +static bool tsc_khz_needed(void *opaque)
> +{
> + X86CPU *cpu = opaque;
> + CPUX86State *env = &cpu->env;
> + MachineClass *mc = MACHINE_GET_CLASS(qdev_get_machine());
> + PCMachineClass *pcmc = PC_MACHINE_CLASS(mc);
> + return env->tsc_khz && pcmc->save_tsc_khz;
> +}
> +
> +static const VMStateDescription vmstate_tsc_khz = {
> + .name = "cpu/tsc_khz",
> + .version_id = 1,
> + .minimum_version_id = 1,
> + .needed = tsc_khz_needed,
> + .fields = (VMStateField[]) {
> + VMSTATE_INT64(env.tsc_khz, X86CPU),
> + VMSTATE_END_OF_LIST()
> + }
> +};
> +
> VMStateDescription vmstate_x86_cpu = {
> .name = "cpu",
> .version_id = 12,
> @@ -895,6 +922,7 @@ VMStateDescription vmstate_x86_cpu = {
> &vmstate_msr_hyperv_runtime,
> &vmstate_avx512,
> &vmstate_xss,
> + &vmstate_tsc_khz,
> NULL
> }
> };
> --
> 2.4.8
>
--
Eduardo
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