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

From: Reinette Chatre
Date: Fri Jun 28 2024 - 12:55:23 EST

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@xxxxxxx>
Signed-off-by: Dave Martin <Dave.Martin@xxxxxxx>
Signed-off-by: James Morse <james.morse@xxxxxxx>
Tested-by: Peter Newman <peternewman@xxxxxxxxxx>
Tested-by: Shaopeng Tan <tan.shaopeng@xxxxxxxxxxxxxx>
---
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