Re: [RFC PATCH v4 14/36] i386/tdx: Implement user specified tsc frequency

[Isaku Yamahata <isaku.yamahata@gmail.com>]

On Thu, May 12, 2022 at 11:17:41AM +0800,
Xiaoyao Li <xiaoyao.li@intel.com> wrote:

> Reuse "-cpu,tsc-frequency=" to get user wanted tsc frequency and pass it
> to KVM_TDX_INIT_VM.
> 
> Besides, sanity check the tsc frequency to be in the legal range and
> legal granularity (required by TDX module).

Just to make it sure.
You didn't use VM-scoped KVM_SET_TSC_KHZ because KVM side patch is still in
kvm/queue?  Once the patch lands, we should use it.

Thanks,

> 
> Signed-off-by: Xiaoyao Li <xiaoyao.li@intel.com>
> ---
>  target/i386/kvm/kvm.c |  8 ++++++++
>  target/i386/kvm/tdx.c | 18 ++++++++++++++++++
>  2 files changed, 26 insertions(+)
> 
> diff --git a/target/i386/kvm/kvm.c b/target/i386/kvm/kvm.c
> index f2d7c3cf59ac..c51125ab200f 100644
> --- a/target/i386/kvm/kvm.c
> +++ b/target/i386/kvm/kvm.c
> @@ -818,6 +818,14 @@ static int kvm_arch_set_tsc_khz(CPUState *cs)
>      int r, cur_freq;
>      bool set_ioctl = false;
>  
> +    /*
> +     * TD guest's TSC is immutable, it cannot be set/changed via
> +     * KVM_SET_TSC_KHZ, but only be initialized via KVM_TDX_INIT_VM
> +     */
> +    if (is_tdx_vm()) {
> +        return 0;
> +    }
> +
>      if (!env->tsc_khz) {
>          return 0;
>      }
> diff --git a/target/i386/kvm/tdx.c b/target/i386/kvm/tdx.c
> index 9f2cdf640b5c..622efc409438 100644
> --- a/target/i386/kvm/tdx.c
> +++ b/target/i386/kvm/tdx.c
> @@ -35,6 +35,9 @@
>  #define TDX_TD_ATTRIBUTES_PKS               BIT_ULL(30)
>  #define TDX_TD_ATTRIBUTES_PERFMON           BIT_ULL(63)
>  
> +#define TDX_MIN_TSC_FREQUENCY_KHZ   (100 * 1000)
> +#define TDX_MAX_TSC_FREQUENCY_KHZ   (10 * 1000 * 1000)
> +
>  static TdxGuest *tdx_guest;
>  
>  /* It's valid after kvm_confidential_guest_init()->kvm_tdx_init() */
> @@ -211,6 +214,20 @@ int tdx_pre_create_vcpu(CPUState *cpu)
>          goto out;
>      }
>  
> +    r = -EINVAL;
> +    if (env->tsc_khz && (env->tsc_khz < TDX_MIN_TSC_FREQUENCY_KHZ ||
> +                         env->tsc_khz > TDX_MAX_TSC_FREQUENCY_KHZ)) {
> +        error_report("Invalid TSC %ld KHz, must specify cpu_frequency between [%d, %d] kHz",
> +                      env->tsc_khz, TDX_MIN_TSC_FREQUENCY_KHZ,
> +                      TDX_MAX_TSC_FREQUENCY_KHZ);
> +        goto out;
> +    }
> +
> +    if (env->tsc_khz % (25 * 1000)) {
> +        error_report("Invalid TSC %ld KHz, it must be multiple of 25MHz", env->tsc_khz);
> +        goto out;
> +    }
> +
>      r = setup_td_guest_attributes(x86cpu);
>      if (r) {
>          goto out;
> @@ -221,6 +238,7 @@ int tdx_pre_create_vcpu(CPUState *cpu)
>  
>      init_vm.attributes = tdx_guest->attributes;
>      init_vm.max_vcpus = ms->smp.cpus;
> +    init_vm.tsc_khz = env->tsc_khz;
>  
>      r = tdx_vm_ioctl(KVM_TDX_INIT_VM, 0, &init_vm);
>      if (r < 0) {
> -- 
> 2.27.0
> 
> 

-- 
Isaku Yamahata <isaku.yamahata@gmail.com>