Re: [PATCH RFC v5 16/18] ACPI: RISC-V: Parse RISC-V Quality of Service Controller (RQSC) table

[Sunil V L]

Hi Drew,

On Mon, May 25, 2026 at 5:32 AM Drew Fustini <fustini@xxxxxxxxxx> wrote:
>
> Add a parser for the ACPI RQSC table, which describes the CBQRI
> controllers in a system. For each table entry, populate a
> cbqri_controller_info descriptor and hand it to the CBQRI driver via
> riscv_cbqri_register_controller(). The driver owns all subsequent state,
> including cpumask resolution at cbqri_resctrl_setup() time.
>
> Link: https://github.com/riscv-non-isa/riscv-rqsc/blob/main/src/
> Link: https://github.com/riscv-non-isa/riscv-cbqri/releases/tag/v1.0
> Assisted-by: Claude:claude-opus-4-7
> Signed-off-by: Drew Fustini <fustini@xxxxxxxxxx>
> ---
>  MAINTAINERS                   |   2 +
>  arch/riscv/include/asm/acpi.h |  10 +++
>  drivers/acpi/riscv/Makefile   |   1 +
>  drivers/acpi/riscv/rqsc.c     | 194 ++++++++++++++++++++++++++++++++++++++++++
>  drivers/acpi/riscv/rqsc.h     |  63 ++++++++++++++
>  5 files changed, 270 insertions(+)
>
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 7821dd5159cb..eab31c7b5e91 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -23025,6 +23025,8 @@ S:      Supported
>  F:     arch/riscv/include/asm/qos.h
>  F:     arch/riscv/include/asm/resctrl.h
>  F:     arch/riscv/kernel/qos.c
> +F:     drivers/acpi/riscv/rqsc.c
> +F:     drivers/acpi/riscv/rqsc.h
>  F:     drivers/resctrl/cbqri_devices.c
>  F:     drivers/resctrl/cbqri_internal.h
>  F:     drivers/resctrl/cbqri_resctrl.c
> diff --git a/arch/riscv/include/asm/acpi.h b/arch/riscv/include/asm/acpi.h
> index 26ab37c171bc..3cfd0102085e 100644
> --- a/arch/riscv/include/asm/acpi.h
> +++ b/arch/riscv/include/asm/acpi.h
> @@ -67,6 +67,16 @@ int acpi_get_riscv_isa(struct acpi_table_header *table,
>
>  void acpi_get_cbo_block_size(struct acpi_table_header *table, u32 *cbom_size,
>                              u32 *cboz_size, u32 *cbop_size);
> +
> +#ifdef CONFIG_RISCV_CBQRI_DRIVER
> +int __init acpi_parse_rqsc(struct acpi_table_header *table);
> +#else
> +static inline int acpi_parse_rqsc(struct acpi_table_header *table)
> +{
> +       return -EINVAL;
> +}
> +#endif /* CONFIG_RISCV_CBQRI_DRIVER */
> +
>  #else
>  static inline void acpi_init_rintc_map(void) { }
>  static inline struct acpi_madt_rintc *acpi_cpu_get_madt_rintc(int cpu)
> diff --git a/drivers/acpi/riscv/Makefile b/drivers/acpi/riscv/Makefile
> index 1284a076fa88..77f8f0101b7e 100644
> --- a/drivers/acpi/riscv/Makefile
> +++ b/drivers/acpi/riscv/Makefile
> @@ -1,5 +1,6 @@
>  # SPDX-License-Identifier: GPL-2.0-only
>  obj-y                                  += rhct.o init.o irq.o
> +obj-$(CONFIG_RISCV_CBQRI_DRIVER)       += rqsc.o
>  obj-$(CONFIG_ACPI_PROCESSOR_IDLE)      += cpuidle.o
>  obj-$(CONFIG_ACPI_CPPC_LIB)            += cppc.o
>  obj-$(CONFIG_ACPI_RIMT)                        += rimt.o
> diff --git a/drivers/acpi/riscv/rqsc.c b/drivers/acpi/riscv/rqsc.c
> new file mode 100644
> index 000000000000..1cbc5c07e191
> --- /dev/null
> +++ b/drivers/acpi/riscv/rqsc.c
> @@ -0,0 +1,194 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +
> +#define pr_fmt(fmt) "ACPI: RQSC: " fmt
> +
> +#include <linux/acpi.h>
> +#include <linux/bits.h>
> +#include <linux/riscv_cbqri.h>
> +
> +#include "rqsc.h"
> +
> +#define CBQRI_CTRL_SIZE 0x1000
> +
> +int __init acpi_parse_rqsc(struct acpi_table_header *table)
> +{
> +       struct acpi_table_rqsc *rqsc = (struct acpi_table_rqsc *)table;
> +       struct acpi_rqsc_node *end, *node;
> +       int num_controllers = 0;
> +
> +       /*
> +        * Reject revisions newer than this parser was written against.  A
> +        * future revision could extend the fixed RQSC header before the
> +        * first node, which would shift the resource subtables and cause the
> +        * sizeof(*node)-based offset below to point into the wrong place.
> +        */
> +       if (rqsc->header.revision != ACPI_RQSC_REVISION) {
> +               pr_err("RQSC table revision %u, expected %u, aborting\n",
> +                      rqsc->header.revision, ACPI_RQSC_REVISION);
> +               return -EINVAL;
> +       }
> +
> +       /* Reject tables shorter than the fixed RQSC header. */
> +       if (rqsc->header.length < sizeof(struct acpi_table_rqsc)) {
> +               pr_err("RQSC table truncated: length %u < %zu, aborting\n",
> +                      rqsc->header.length, sizeof(struct acpi_table_rqsc));
> +               return -EINVAL;
> +       }
> +
> +       end = ACPI_ADD_PTR(struct acpi_rqsc_node, rqsc, rqsc->header.length);
> +
> +       for (node = ACPI_ADD_PTR(struct acpi_rqsc_node, rqsc,
> +                                sizeof(struct acpi_table_rqsc));
> +            node < end;
> +            node = ACPI_ADD_PTR(struct acpi_rqsc_node, node, node->length)
> +       ) {
> +               const struct acpi_rqsc_resource *res0;
> +               struct cbqri_controller_info info = {};
> +               int ret;
> +
> +               if ((void *)node + sizeof(*node) > (void *)end) {
> +                       pr_err("truncated entry at end of table, aborting\n");
> +                       riscv_cbqri_unregister_last(num_controllers);
> +                       return -EINVAL;
> +               }
> +
> +               if (node->length < sizeof(*node)) {
> +                       pr_err("malformed RQSC entry: length %u < %zu, aborting\n",
> +                              node->length, sizeof(*node));
> +                       riscv_cbqri_unregister_last(num_controllers);
> +                       return -EINVAL;
> +               }
> +
> +               /*
> +                * Without this check, a node whose length claims to extend
> +                * past the end of the table would advance the loop cursor
> +                * past `end` and silently terminate.  Flag the corruption
> +                * explicitly so a malformed firmware table cannot truncate
> +                * the controller list without noise.
> +                */
> +               if ((void *)node + node->length > (void *)end) {
> +                       pr_err("RQSC entry length %u overruns table end, aborting\n",
> +                              node->length);
> +                       riscv_cbqri_unregister_last(num_controllers);
> +                       return -EINVAL;
> +               }
> +
> +               /* GAS must describe system memory. ioremap() consumes it later. */
> +               if (node->reg.space_id != ACPI_ADR_SPACE_SYSTEM_MEMORY) {
> +                       pr_warn("controller has unsupported address space_id=%u, skipping\n",
> +                               node->reg.space_id);
> +                       continue;
> +               }
> +
> +               /* Address 0 would map page 0 (reset vectors, SBI, boot ROM). */
> +               if (!node->reg.address) {
> +                       pr_warn("controller has zero address, skipping\n");
> +                       continue;
> +               }
> +
> +               info.type = node->type;
> +               /* RQSC v0.9.2 section 2 Table 2: 12-byte GAS-format register interface address */
> +               info.addr = node->reg.address;
> +               info.size = CBQRI_CTRL_SIZE;
> +               info.rcid_count = node->rcid;
> +               info.mcid_count = node->mcid;
> +
> +               /* See CBQRI_MAX_RCID/MCID in <linux/riscv_cbqri.h> for the rationale. */
> +               if (info.rcid_count > CBQRI_MAX_RCID) {
> +                       pr_warn("controller at %pa: rcid_count %u exceeds CBQRI_MAX_RCID %u, skipping\n",
> +                               &info.addr, info.rcid_count, CBQRI_MAX_RCID);
> +                       continue;
> +               }
> +
> +               if (info.mcid_count > CBQRI_MAX_MCID) {
> +                       pr_warn("controller at %pa: mcid_count %u exceeds CBQRI_MAX_MCID %u, skipping\n",
> +                               &info.addr, info.mcid_count, CBQRI_MAX_MCID);
> +                       continue;
> +               }
> +
Do you also want to add a check for the statement in the spec "At
least one of RCID Count or MCID Count must be non-zero." ?

> +               if (node->nres == 0) {
> +                       pr_warn("controller at %pa has no resource descriptors, skipping\n",
> +                               &info.addr);
> +                       continue;
> +               }
> +
> +               /*
> +                * Resources follow the node header in-line. Only res[0] is
> +                * consumed. Bound it against end before reading its prefix so
> +                * a table that ends partway through a resource subtable is
> +                * rejected rather than read past the mapping.
> +                */
> +               res0 = (const struct acpi_rqsc_resource *)
> +                      ((const u8 *)node + sizeof(*node));
> +               if ((void *)res0 + sizeof(*res0) > (void *)end ||
> +                   node->length < sizeof(*node) + sizeof(*res0) ||
> +                   res0->length < sizeof(*res0)) {
> +                       pr_warn("controller at %pa: node too short for resource descriptor, skipping\n",
> +                               &info.addr);
> +                       continue;
> +               }
> +
> +               if (node->nres > 1)
> +                       pr_warn("controller at %pa has %u resource descriptors, using first\n",
> +                               &info.addr, node->nres);
> +
> +               /*
> +                * id1 is u64 on the wire but cache_id and prox_dom are u32
> +                * downstream (PPTT cache_id, ACPI proximity domain). Reject
> +                * rather than truncate, so a too-large id is not silently
> +                * mapped to the wrong PPTT entry or NUMA node.
> +                */
> +               if (res0->id1 > U32_MAX) {
> +                       pr_warn("controller at %pa: id1 0x%llx exceeds u32, skipping\n",
> +                               &info.addr, res0->id1);
> +                       continue;
> +               }
> +
> +               /*
> +                * Pair the QoS controller type with the resource descriptor
> +                * fields that index id1.  RQSC v0.9.2 Table 4 defines the
> +                * mapping: a Capacity controller indexes a Processor Cache
> +                * via PPTT cache_id, a Bandwidth controller indexes a Memory
> +                * Range via SRAT proximity domain.  Mismatched pairings
> +                * (e.g. a CC whose first resource is Memory) would otherwise
> +                * route id1 into the wrong downstream lookup.
> +                */
> +               switch (info.type) {
> +               case CBQRI_CONTROLLER_TYPE_CAPACITY:
> +                       if (res0->type != ACPI_RQSC_RESOURCE_TYPE_CACHE ||
> +                           res0->id_type != ACPI_RQSC_RESOURCE_ID_TYPE_PROCESSOR_CACHE) {
> +                               pr_warn("CC at %pa: resource type=%u id_type=%u not (cache, processor cache), skipping\n",
> +                                       &info.addr, res0->type, res0->id_type);
> +                               continue;
> +                       }
> +                       info.cache_id = (u32)res0->id1;
> +                       break;
> +               case CBQRI_CONTROLLER_TYPE_BANDWIDTH:
> +                       if (res0->type != ACPI_RQSC_RESOURCE_TYPE_MEMORY ||
> +                           res0->id_type != ACPI_RQSC_RESOURCE_ID_TYPE_MEMORY_RANGE) {
> +                               pr_warn("BC at %pa: resource type=%u id_type=%u not (memory, memory range), skipping\n",
> +                                       &info.addr, res0->type, res0->id_type);
> +                               continue;
> +                       }
> +                       info.prox_dom = (u32)res0->id1;
> +                       break;
> +               default:
> +                       pr_warn("controller at %pa: unknown type %u, skipping\n",
> +                               &info.addr, info.type);
> +                       continue;
> +               }
> +
> +               pr_debug("registering controller type=%u addr=%pa rcid=%u mcid=%u\n",
> +                        info.type, &info.addr, info.rcid_count, info.mcid_count);
> +
> +               ret = riscv_cbqri_register_controller(&info);
> +               if (ret == 0)
> +                       num_controllers++;
> +               else
> +                       pr_warn("controller at %pa: registration failed (%d), skipping\n",
> +                               &info.addr, ret);
> +       }
> +
> +       pr_info("found %d CBQRI controllers\n", num_controllers);
> +       return 0;
> +}
> diff --git a/drivers/acpi/riscv/rqsc.h b/drivers/acpi/riscv/rqsc.h
> new file mode 100644
> index 000000000000..f7b556f29e16
> --- /dev/null
> +++ b/drivers/acpi/riscv/rqsc.h
> @@ -0,0 +1,63 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +/*
> + * Local definitions for the RISC-V Quality of Service Controller (RQSC)
> + * ACPI table. Will move to ACPICA's include/acpi/actbl2.h once the spec
> + * is ratified.
> + */
> +#ifndef _DRIVERS_ACPI_RISCV_RQSC_H
> +#define _DRIVERS_ACPI_RISCV_RQSC_H
> +
> +#include <linux/types.h>
> +#include <acpi/actbl.h>
> +
> +#define ACPI_SIG_RQSC  "RQSC"  /* RISC-V Quality of Service Controller */
> +
> +/* RQSC v0.9.2 Table 1: current revision number. */
> +#define ACPI_RQSC_REVISION     1
> +
> +/* RQSC v0.9.2 Table 4: Resource Type values for acpi_rqsc_resource.type. */
> +#define ACPI_RQSC_RESOURCE_TYPE_CACHE  0
> +#define ACPI_RQSC_RESOURCE_TYPE_MEMORY 1
> +
> +/* RQSC v0.9.2 Table 4: Resource ID Type values for .id_type. */
> +#define ACPI_RQSC_RESOURCE_ID_TYPE_PROCESSOR_CACHE     0
> +#define ACPI_RQSC_RESOURCE_ID_TYPE_MEMORY_RANGE                1
> +
Memory-Side Cache, ACPI, PCI devices missing?

Thanks,
Sunil