Re: [Xen-devel] [PATCH v3 08/13] x86/hvm: Setup TSC scaling ratio

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 31.12.15 at 04:03, <haozhong.zhang@xxxxxxxxx> wrote:
> @@ -301,6 +302,42 @@ int hvm_set_guest_pat(struct vcpu *v, u64 guest_pat)
>      return 1;
>  }
>  
> +bool_t hvm_validate_tsc_scaling_ratio(uint32_t gtsc_khz)
> +{
> +    u64 ratio;
> +
> +    if ( !hvm_funcs.tsc_scaling_supported )
> +        return FALSE;

We use 0 and 1, not FALSE and TRUE (except in ACPI and EFI code).

> +    ratio = mul_u64_u32_div(1ULL << hvm_funcs.tsc_scaling_ratio_frac_bits,
> +                            gtsc_khz, cpu_khz);
> +
> +    return (!ratio || ratio > hvm_funcs.max_tsc_scaling_ratio) ? FALSE : 
> TRUE;

There no point in using a conditional expression here.

> --- a/xen/include/asm-x86/hvm/hvm.h
> +++ b/xen/include/asm-x86/hvm/hvm.h
> @@ -226,6 +226,9 @@ struct hvm_function_table {
>      int (*altp2m_vcpu_emulate_vmfunc)(struct cpu_user_regs *regs);
>  
>      uint64_t (*scale_tsc)(struct vcpu *v, uint64_t tsc);
> +
> +    /* Architecture function to setup TSC scaling ratio */
> +    void (*setup_tsc_scaling)(struct vcpu *v);

SVM doesn't use this hook, and VMX gets to use it only later. I.e.
everything related to it is dead code right now, and would therefore
better go into the VMX (I suppose) patch actually making use of it.

Jan


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