Re: [PATCH] x86/spec: fix reporting of BHB clearing usage from guest entry points

[Jan Beulich <jbeulich@xxxxxxxx>]

On 15.04.2024 16:17, Roger Pau Monne wrote:
> --- a/xen/arch/x86/spec_ctrl.c
> +++ b/xen/arch/x86/spec_ctrl.c
> @@ -643,7 +643,7 @@ static void __init print_details(enum ind_thunk thunk)
>             opt_eager_fpu                             ? " EAGER_FPU"     : "",
>             opt_verw_hvm                              ? " VERW"          : "",
>             boot_cpu_has(X86_FEATURE_IBPB_ENTRY_HVM)  ? " IBPB-entry"    : "",
> -           cpu_has_bhb_seq                           ? " BHB-entry"     : 
> "");
> +           opt_bhb_entry_hvm                         ? " BHB-entry"     : 
> "");
>  
>  #endif
>  #ifdef CONFIG_PV
> @@ -658,7 +658,7 @@ static void __init print_details(enum ind_thunk thunk)
>             opt_eager_fpu                             ? " EAGER_FPU"     : "",
>             opt_verw_pv                               ? " VERW"          : "",
>             boot_cpu_has(X86_FEATURE_IBPB_ENTRY_PV)   ? " IBPB-entry"    : "",
> -           cpu_has_bhb_seq                           ? " BHB-entry"     : 
> "");
> +           opt_bhb_entry_pv                          ? " BHB-entry"     : 
> "");
>  
>      printk("  XPTI (64-bit PV only): Dom0 %s, DomU %s (with%s PCID)\n",
>             opt_xpti_hwdom ? "enabled" : "disabled",

For one the surrounding if() conditions need similar adjustment.

But then I wonder whether the further uses of cpu_has_bhb_seq don't
need switching, too (when determining whether to force
X86_SPEC_NO_LFENCE_ENTRY_*). At which point the question is why
cpu_has_bhb_seq exists in the first place: It in particular does not
affect the default calculation of opt_bhb_entry_*, afaics.

Jan