From: Fenghua Yu <fenghua.yu@intel.com>

Add the interface in resctrl FS to show if sparse cache allocation
bit masks are supported on the platform. Reading the file returns
either a "1" if non-contiguous 1s are supported and "0" otherwise.
The file path is /sys/fs/resctrl/info/{resource}/sparse_masks, where
{resource} can be either "L2" or "L3".

Signed-off-by: Fenghua Yu <fenghua.yu@intel.com>
Reviewed-by: Peter Newman <peternewman@google.com>
Tested-by: Peter Newman <peternewman@google.com>
Signed-off-by: Maciej Wieczor-Retman <maciej.wieczor-retman@intel.com>
---
Changelog v3:
- Add Peter's tested-by and reviewed-by tags.
- Reword patch message slightly. (Reinette)

Changelog v2:
- Change bitmap naming convention to bit mask. (Reinette)
- Change file name to "sparse_masks". (Reinette)

 arch/x86/kernel/cpu/resctrl/rdtgroup.c | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
index 725344048f85..945801898a4d 100644
--- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
+++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
@@ -895,6 +895,17 @@ static int rdt_shareable_bits_show(struct kernfs_open_file *of,
 	return 0;
 }
 
+static int rdt_has_sparse_bitmasks_show(struct kernfs_open_file *of,
+					struct seq_file *seq, void *v)
+{
+	struct resctrl_schema *s = of->kn->parent->priv;
+	struct rdt_resource *r = s->res;
+
+	seq_printf(seq, "%u\n", r->cache.arch_has_sparse_bitmasks);
+
+	return 0;
+}
+
 /**
  * rdt_bit_usage_show - Display current usage of resources
  *
@@ -1839,6 +1850,13 @@ static struct rftype res_common_files[] = {
 		.seq_show	= rdtgroup_size_show,
 		.fflags		= RF_CTRL_BASE,
 	},
+	{
+		.name		= "sparse_masks",
+		.mode		= 0444,
+		.kf_ops		= &rdtgroup_kf_single_ops,
+		.seq_show	= rdt_has_sparse_bitmasks_show,
+		.fflags		= RF_CTRL_INFO | RFTYPE_RES_CACHE,
+	},
 
 };
 
-- 
2.42.0

On Fri, 29 Sep 2023, Maciej Wieczor-Retman wrote:

> From: Fenghua Yu <fenghua.yu@intel.com>
> 
> Add the interface in resctrl FS to show if sparse cache allocation
> bit masks are supported on the platform. Reading the file returns
> either a "1" if non-contiguous 1s are supported and "0" otherwise.
> The file path is /sys/fs/resctrl/info/{resource}/sparse_masks, where
> {resource} can be either "L2" or "L3".
> 
> Signed-off-by: Fenghua Yu <fenghua.yu@intel.com>
> Reviewed-by: Peter Newman <peternewman@google.com>
> Tested-by: Peter Newman <peternewman@google.com>
> Signed-off-by: Maciej Wieczor-Retman <maciej.wieczor-retman@intel.com>
> ---
> Changelog v3:
> - Add Peter's tested-by and reviewed-by tags.
> - Reword patch message slightly. (Reinette)
> 
> Changelog v2:
> - Change bitmap naming convention to bit mask. (Reinette)
> - Change file name to "sparse_masks". (Reinette)
> 
>  arch/x86/kernel/cpu/resctrl/rdtgroup.c | 18 ++++++++++++++++++
>  1 file changed, 18 insertions(+)
> 
> diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> index 725344048f85..945801898a4d 100644
> --- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> +++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> @@ -895,6 +895,17 @@ static int rdt_shareable_bits_show(struct kernfs_open_file *of,
>  	return 0;
>  }
>  
> +static int rdt_has_sparse_bitmasks_show(struct kernfs_open_file *of,
> +					struct seq_file *seq, void *v)
> +{
> +	struct resctrl_schema *s = of->kn->parent->priv;
> +	struct rdt_resource *r = s->res;
> +
> +	seq_printf(seq, "%u\n", r->cache.arch_has_sparse_bitmasks);
> +
> +	return 0;
> +}
> +
>  /**
>   * rdt_bit_usage_show - Display current usage of resources
>   *
> @@ -1839,6 +1850,13 @@ static struct rftype res_common_files[] = {
>  		.seq_show	= rdtgroup_size_show,
>  		.fflags		= RF_CTRL_BASE,
>  	},
> +	{
> +		.name		= "sparse_masks",
> +		.mode		= 0444,
> +		.kf_ops		= &rdtgroup_kf_single_ops,
> +		.seq_show	= rdt_has_sparse_bitmasks_show,
> +		.fflags		= RF_CTRL_INFO | RFTYPE_RES_CACHE,
> +	},
>  
>  };
>  
> 

Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>

-- 
 i.