Re: [PATCH v3 36/38] fs/resctrl: Add boiler plate for external resctrl code

[Reinette Chatre <reinette.chatre@intel.com>]

Hi James,

On 6/14/24 8:00 AM, James Morse wrote:
> Add Makefile and Kconfig for fs/resctrl. Add ARCH_HAS_CPU_RESCTRL
> for the common parts of the resctrl interface and make X86_CPU_RESCTRL
> depend on this.
> 
> Adding an include of asm/resctrl.h to linux/resctrl.h allows some
> of the files to switch over to using this header instead.
> 
> Co-developed-by: Dave Martin <Dave.Martin@arm.com>
> Signed-off-by: Dave Martin <Dave.Martin@arm.com>
> Signed-off-by: James Morse <james.morse@arm.com>
> Tested-by: Peter Newman <peternewman@google.com>
> Tested-by: Shaopeng Tan <tan.shaopeng@jp.fujitsu.com>
> ---
> Changes since v2:
>   * Dropped KERNFS dependency from arch side Kconfig.
>   * Added empty trace.h file.
>   * Merged asm->linux includes from Dave's patch to decouple those
>     patches from this series.
> 
> Changes since v1:
>   * Rename new file psuedo_lock.c to pseudo_lock.c, to match the name
>     of the original file (and to be less surprising).
> 
>   * [Whitespace only] Under RESCTRL_FS in fs/resctrl/Kconfig, delete
>     alignment space in orphaned select ... if (which has nothing to line
>     up with any more).
> 
>   * [Whitespace only] Reflow and re-tab Kconfig additions.
> ---
>   MAINTAINERS                               |  1 +
>   arch/Kconfig                              |  8 +++++
>   arch/x86/Kconfig                          |  5 ++--
>   arch/x86/kernel/cpu/resctrl/internal.h    |  3 +-
>   arch/x86/kernel/cpu/resctrl/monitor.c     |  2 +-
>   arch/x86/kernel/cpu/resctrl/pseudo_lock.c |  2 +-
>   arch/x86/kernel/cpu/resctrl/rdtgroup.c    |  2 +-
>   fs/Kconfig                                |  1 +
>   fs/Makefile                               |  1 +
>   fs/resctrl/Kconfig                        | 36 +++++++++++++++++++++++
>   fs/resctrl/Makefile                       |  3 ++
>   fs/resctrl/ctrlmondata.c                  |  0
>   fs/resctrl/internal.h                     |  0
>   fs/resctrl/monitor.c                      |  0
>   fs/resctrl/pseudo_lock.c                  |  0
>   fs/resctrl/rdtgroup.c                     |  0
>   fs/resctrl/trace.h                        |  0
>   include/linux/resctrl.h                   |  4 +++
>   18 files changed, 61 insertions(+), 7 deletions(-)
>   create mode 100644 fs/resctrl/Kconfig
>   create mode 100644 fs/resctrl/Makefile
>   create mode 100644 fs/resctrl/ctrlmondata.c
>   create mode 100644 fs/resctrl/internal.h
>   create mode 100644 fs/resctrl/monitor.c
>   create mode 100644 fs/resctrl/pseudo_lock.c
>   create mode 100644 fs/resctrl/rdtgroup.c
>   create mode 100644 fs/resctrl/trace.h
> 
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 441b039068d8..64195c298baf 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -18859,6 +18859,7 @@ S:	Supported
>   F:	Documentation/arch/x86/resctrl*
>   F:	arch/x86/include/asm/resctrl.h
>   F:	arch/x86/kernel/cpu/resctrl/
> +F:	fs/resctrl/
>   F:	include/linux/resctrl*.h
>   F:	tools/testing/selftests/resctrl/
>   
> diff --git a/arch/Kconfig b/arch/Kconfig
> index 975dd22a2dbd..4156604dd926 100644
> --- a/arch/Kconfig
> +++ b/arch/Kconfig
> @@ -1431,6 +1431,14 @@ config STRICT_MODULE_RWX
>   config ARCH_HAS_PHYS_TO_DMA
>   	bool
>   
> +config ARCH_HAS_CPU_RESCTRL
> +	bool
> +	help
> +	  An architecture selects this option to indicate that the necessary
> +	  hooks are provided to support the common memory system usage
> +	  monitoring and control interfaces provided by the 'resctrl'
> +	  filesystem (see RESCTRL_FS).
> +
>   config HAVE_ARCH_COMPILER_H
>   	bool
>   	help
> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
> index 446984277b45..e4dd4097e10f 100644
> --- a/arch/x86/Kconfig
> +++ b/arch/x86/Kconfig
> @@ -490,8 +490,9 @@ config X86_MPPARSE
>   config X86_CPU_RESCTRL
>   	bool "x86 CPU resource control support"
>   	depends on X86 && (CPU_SUP_INTEL || CPU_SUP_AMD)
> -	select KERNFS
> -	select PROC_CPU_RESCTRL		if PROC_FS
> +	depends on MISC_FILESYSTEMS
> +	select ARCH_HAS_CPU_RESCTRL
> +	select RESCTRL_FS
>   	select RESCTRL_FS_PSEUDO_LOCK
>   	help
>   	  Enable x86 CPU resource control support.
> diff --git a/arch/x86/kernel/cpu/resctrl/internal.h b/arch/x86/kernel/cpu/resctrl/internal.h
> index bad103f20663..6f6785a31efe 100644
> --- a/arch/x86/kernel/cpu/resctrl/internal.h
> +++ b/arch/x86/kernel/cpu/resctrl/internal.h
> @@ -7,10 +7,9 @@
>   #include <linux/kernfs.h>
>   #include <linux/fs_context.h>
>   #include <linux/jump_label.h>
> +#include <linux/resctrl.h>
>   #include <linux/tick.h>
>   
> -#include <asm/resctrl.h>
> -
>   #define L3_QOS_CDP_ENABLE		0x01ULL
>   
>   #define L2_QOS_CDP_ENABLE		0x01ULL
> diff --git a/arch/x86/kernel/cpu/resctrl/monitor.c b/arch/x86/kernel/cpu/resctrl/monitor.c
> index 145bd05eafa5..a1539edb25fa 100644
> --- a/arch/x86/kernel/cpu/resctrl/monitor.c
> +++ b/arch/x86/kernel/cpu/resctrl/monitor.c
> @@ -17,11 +17,11 @@
>   
>   #include <linux/cpu.h>
>   #include <linux/module.h>
> +#include <linux/resctrl.h>
>   #include <linux/sizes.h>
>   #include <linux/slab.h>
>   
>   #include <asm/cpu_device_id.h>
> -#include <asm/resctrl.h>
>   
>   #include "internal.h"
>   #include "trace.h"
> diff --git a/arch/x86/kernel/cpu/resctrl/pseudo_lock.c b/arch/x86/kernel/cpu/resctrl/pseudo_lock.c
> index c096fa106b80..97e901009c91 100644
> --- a/arch/x86/kernel/cpu/resctrl/pseudo_lock.c
> +++ b/arch/x86/kernel/cpu/resctrl/pseudo_lock.c
> @@ -19,12 +19,12 @@
>   #include <linux/mman.h>
>   #include <linux/perf_event.h>
>   #include <linux/pm_qos.h>
> +#include <linux/resctrl.h>
>   #include <linux/slab.h>
>   #include <linux/uaccess.h>
>   
>   #include <asm/cacheflush.h>
>   #include <asm/cpu_device_id.h>
> -#include <asm/resctrl.h>
>   #include <asm/perf_event.h>
>   
>   #include "../../events/perf_event.h" /* For X86_CONFIG() */
> diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> index 969c454b67f1..c7cbd30ac0f2 100644
> --- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> +++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> @@ -19,6 +19,7 @@
>   #include <linux/fs_parser.h>
>   #include <linux/sysfs.h>
>   #include <linux/kernfs.h>
> +#include <linux/resctrl.h>
>   #include <linux/seq_buf.h>
>   #include <linux/seq_file.h>
>   #include <linux/sched/signal.h>
> @@ -29,7 +30,6 @@
>   
>   #include <uapi/linux/magic.h>
>   
> -#include <asm/resctrl.h>
>   #include "internal.h"
>   
>   DEFINE_STATIC_KEY_FALSE(rdt_enable_key);
> diff --git a/fs/Kconfig b/fs/Kconfig
> index a46b0cbc4d8f..d8a36383b6dc 100644
> --- a/fs/Kconfig
> +++ b/fs/Kconfig
> @@ -331,6 +331,7 @@ source "fs/omfs/Kconfig"
>   source "fs/hpfs/Kconfig"
>   source "fs/qnx4/Kconfig"
>   source "fs/qnx6/Kconfig"
> +source "fs/resctrl/Kconfig"
>   source "fs/romfs/Kconfig"
>   source "fs/pstore/Kconfig"
>   source "fs/sysv/Kconfig"
> diff --git a/fs/Makefile b/fs/Makefile
> index 6ecc9b0a53f2..da6e2d028722 100644
> --- a/fs/Makefile
> +++ b/fs/Makefile
> @@ -129,3 +129,4 @@ obj-$(CONFIG_EFIVAR_FS)		+= efivarfs/
>   obj-$(CONFIG_EROFS_FS)		+= erofs/
>   obj-$(CONFIG_VBOXSF_FS)		+= vboxsf/
>   obj-$(CONFIG_ZONEFS_FS)		+= zonefs/
> +obj-$(CONFIG_RESCTRL_FS)	+= resctrl/
> diff --git a/fs/resctrl/Kconfig b/fs/resctrl/Kconfig
> new file mode 100644
> index 000000000000..a5fbda54d32f
> --- /dev/null
> +++ b/fs/resctrl/Kconfig
> @@ -0,0 +1,36 @@
> +config RESCTRL_FS
> +	bool "CPU Resource Control Filesystem (resctrl)"
> +	depends on ARCH_HAS_CPU_RESCTRL
> +	select KERNFS
> +	select PROC_CPU_RESCTRL if PROC_FS
> +	help
> +	  Some architectures provide hardware facilities to group tasks and
> +	  monitor and control their usage of memory system resources such as
> +	  caches and memory bandwidth.  Examples of such facilities include
> +	  Intel's Resource Director Technology (Intel(R) RDT) and AMD's
> +	  Platform Quality of Service (AMD QoS).
> +
> +	  If your system has the necessary support and you want to be able to
> +	  assign tasks to groups and manipulate the associated resource
> +	  monitors and controls from userspace, say Y here to get a mountable
> +	  'resctrl' filesystem that lets you do just that.
> +
> +	  If nothing mounts or prods the 'resctrl' filesystem, resource
> +	  controls and monitors are left in a quiescent, permissive state.
> +
> +	  If unsure, it is safe to say N.
> +

Will user ever get opportunity to say "Y" or "N"? It looks to me that
RESCTRL_FS will be "forced" on user as it is selected by the arch specific
config X86_CPU_RESCTRL and be invisble otherwise because of the dependency
on ARCH_HAS_CPU_RESCTRL. The text about when to select "Y" or "N" thus does
not look practical to me and it may be helpful to instead provide
information about when it is selected? I do not know the customs for this
text and if it is intended to document any future usages also.


Reinette