[PATCH RFC v3 07/11] RISC-V: QoS: enable resctrl support for Ssqosid

Drew Fustini
2026-04-15T01:56:56Z

Wire up the RISC-V QoS resctrl implementation:

Add a late_initcall that checks for the Ssqosid extension and, if
present, calls qos_resctrl_setup() to probe CBQRI controllers and
initialize the resctrl filesystem, then registers CPU hotplug callbacks.

Make CONFIG_RISCV_ISA_SSQOSID select ARCH_HAS_CPU_RESCTRL and
RESCTRL_FS, and depends on MISC_FILESYSTEMS.

Add qos_resctrl.o to the build when CONFIG_RISCV_ISA_SSQOSID is set.

Co-developed-by: Adrien Ricciardi <aricciardi@baylibre.com>
Signed-off-by: Adrien Ricciardi <aricciardi@baylibre.com>
Signed-off-by: Drew Fustini <fustini@kernel.org>
---
arch/riscv/Kconfig | 3 +++
arch/riscv/kernel/qos/Makefile | 2 +-
arch/riscv/kernel/qos/qos.c | 32 ++++++++++++++++++++++++++++++++
3 files changed, 36 insertions(+), 1 deletion(-)

diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index 92d2265a0c61..b2fef15b3d4f 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -597,7 +597,10 @@ config RISCV_ISA_SVNAPOT

config RISCV_ISA_SSQOSID
bool "Ssqosid extension support for supervisor mode Quality of Service ID"
+ depends on MISC_FILESYSTEMS
default n
+ select ARCH_HAS_CPU_RESCTRL
+ select RESCTRL_FS
help
Adds support for the Ssqosid ISA extension (Supervisor-mode
Quality of Service ID).
diff --git a/arch/riscv/kernel/qos/Makefile b/arch/riscv/kernel/qos/Makefile
index 9f996263a86d..9ed0c13a854d 100644
--- a/arch/riscv/kernel/qos/Makefile
+++ b/arch/riscv/kernel/qos/Makefile
@@ -1,2 +1,2 @@
# SPDX-License-Identifier: GPL-2.0
-obj-$(CONFIG_RISCV_ISA_SSQOSID) += qos.o
+obj-$(CONFIG_RISCV_ISA_SSQOSID) += qos.o qos_resctrl.o
diff --git a/arch/riscv/kernel/qos/qos.c b/arch/riscv/kernel/qos/qos.c
index a3c2b910e2e0..560607abf10a 100644
--- a/arch/riscv/kernel/qos/qos.c
+++ b/arch/riscv/kernel/qos/qos.c
@@ -1,8 +1,40 @@
// SPDX-License-Identifier: GPL-2.0-only
+#include <linux/slab.h>
+#include <linux/err.h>
+#include <linux/cpu.h>
+#include <linux/cpumask.h>
+#include <linux/riscv_qos.h>
+
+#include <asm/csr.h>
#include <asm/qos.h>

+#include "internal.h"
+
/* cached value of srmcfg csr for each cpu */
DEFINE_PER_CPU(u32, cpu_srmcfg);

/* default srmcfg value for each cpu, set via resctrl cpu assignment */
DEFINE_PER_CPU(u32, cpu_srmcfg_default);
+
+static int __init qos_arch_late_init(void)
+{
+ int err;
+
+ if (!riscv_isa_extension_available(NULL, SSQOSID))
+ return -ENODEV;
+
+ err = qos_resctrl_setup();
+ if (err)
+ return err;
+
+ err = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "qos:online",
+ qos_resctrl_online_cpu,
+ qos_resctrl_offline_cpu);
+ if (err < 0) {
+ resctrl_exit();
+ return err;
+ }
+
+ return 0;
+}
+late_initcall(qos_arch_late_init);

--
2.43.0