Re: [patch 3/3] KVM: x86: frequency change hypercalls

Marcelo Tosatti
2017-02-02T18:04:57Z

On Thu, Feb 02, 2017 at 03:47:58PM -0200, Marcelo Tosatti wrote:
> Implement min/max/up/down frequency change
> KVM hypercalls. To be used by DPDK implementation.
>
> Also allow such hypercalls from guest userspace.
>
> Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
>
> ---
> Documentation/virtual/kvm/hypercalls.txt | 45 +++++++++++++++++++
> arch/x86/kvm/x86.c | 71 ++++++++++++++++++++++++++++++-
> include/uapi/linux/kvm_para.h | 5 ++
> 3 files changed, 120 insertions(+), 1 deletion(-)
>
> Index: kvm-pvfreq/arch/x86/kvm/x86.c
> ===================================================================
> --- kvm-pvfreq.orig/arch/x86/kvm/x86.c 2017-02-02 11:17:17.063756725 -0200
> +++ kvm-pvfreq/arch/x86/kvm/x86.c 2017-02-02 11:17:17.822752510 -0200
> @@ -6219,10 +6219,58 @@
> kvm_x86_ops->refresh_apicv_exec_ctrl(vcpu);
> }
>
> +#ifdef CONFIG_CPU_FREQ_GOV_USERSPACE
> +/* call into cpufreq-userspace governor */
> +static int kvm_pvfreq_up(struct kvm_vcpu *vcpu)
> +{
> + int ret;
> + int cpu = get_cpu();
> +
> + ret = cpufreq_userspace_freq_up(cpu);
> + put_cpu();
> +
> + return ret;
> +}
> +
> +static int kvm_pvfreq_down(struct kvm_vcpu *vcpu)
> +{
> + int ret;
> + int cpu = get_cpu();
> +
> + ret = cpufreq_userspace_freq_down(cpu);
> + put_cpu();
> +
> + return ret;
> +}
> +
> +static int kvm_pvfreq_max(struct kvm_vcpu *vcpu)
> +{
> + int ret;
> + int cpu = get_cpu();
> +
> + ret = cpufreq_userspace_freq_max(cpu);
> + put_cpu();
> +
> + return ret;
> +}
> +
> +static int kvm_pvfreq_min(struct kvm_vcpu *vcpu)
> +{
> + int ret;
> + int cpu = get_cpu();
> +
> + ret = cpufreq_userspace_freq_min(cpu);
> + put_cpu();
> +
> + return ret;
> +}
> +#endif
> +
> int kvm_emulate_hypercall(struct kvm_vcpu *vcpu)
> {
> unsigned long nr, a0, a1, a2, a3, ret;
> int op_64_bit, r;
> + bool cpl_check;
>
> r = kvm_skip_emulated_instruction(vcpu);
>
> @@ -6246,7 +6294,13 @@
> a3 &= 0xFFFFFFFF;
> }
>
> - if (kvm_x86_ops->get_cpl(vcpu) != 0) {
> + cpl_check = true;
> + if (nr == KVM_HC_FREQ_UP || nr == KVM_HC_FREQ_DOWN ||
> + nr == KVM_HC_FREQ_MIN || nr == KVM_HC_FREQ_MAX)
> + if (vcpu->arch.allow_freq_hypercall == true)
> + cpl_check = false;
> +
> + if (cpl_check == true && kvm_x86_ops->get_cpl(vcpu) != 0) {
> ret = -KVM_EPERM;
> goto out;

This should fail with EPERM if vcpu->arch.allow_freq_hypercall ==
false, independently of CPL level.

Will resend with that (and other comments) in v2.