Re: [PATCH v11 07/23] x86/resctrl: Add special case for Intel Haswell enumeration

[Reinette Chatre]

Hi Tony,

On 8/31/26 10:44 AM, Tony Luck wrote:
> Certain Intel Haswell CPUs have support for resctrl L3 cache allocation
> but do not enumerate the feature. There is a quirk to check for support
> and provide hard-coded parameters. This quirk sets rdt_alloc_capable
> to indicate to get_rdt_alloc_resources() that normal enumeration is
> not needed.
> 
> Replace the set and test of rdt_alloc_capable with a new variable
> in preparation for the removal of rdt_alloc_capable.
> 
> Signed-off-by: Tony Luck <tony.luck@xxxxxxxxx>
> ---
> v11:
> 	New patch
> 
>  arch/x86/kernel/cpu/resctrl/core.c | 7 +++++--
>  1 file changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/x86/kernel/cpu/resctrl/core.c b/arch/x86/kernel/cpu/resctrl/core.c
> index b657eab4eb0c..62b97e357ce5 100644
> --- a/arch/x86/kernel/cpu/resctrl/core.c
> +++ b/arch/x86/kernel/cpu/resctrl/core.c
> @@ -138,6 +138,9 @@ struct rdt_resource *resctrl_arch_get_resource(enum resctrl_res_level l)
>  	return &rdt_resources_all[l].r_resctrl;
>  }
>  
> +/* Skip regular allocation if cache_alloc_hsw_probe() succeeds. */
> +static bool hsw_alloc_capable;
> +
>  /*
>   * cache_alloc_hsw_probe() - Have to probe for Intel haswell server CPUs
>   * as they do not have CPUID enumeration support for Cache allocation.
> @@ -178,7 +181,7 @@ static inline void cache_alloc_hsw_probe(void)
>  	r->cache.arch_has_sparse_bitmasks = false;
>  	r->alloc_capable = true;
>  
> -	rdt_alloc_capable = true;
> +	hsw_alloc_capable = true;
>  }
>  
>  /*
> @@ -930,7 +933,7 @@ static __init bool get_rdt_alloc_resources(void)
>  	struct rdt_resource *r;
>  	bool ret = false;
>  
> -	if (rdt_alloc_capable)
> +	if (hsw_alloc_capable)

Could this instead be replaced with:

	if (resctrl_alloc_capable())
		return true;

>  		return true;
>  
>  	if (!boot_cpu_has(X86_FEATURE_RDT_A))

Reinette