From: Ben Horgan Date: Wed, 6 May 2026 08:28:52 +0000 (+0100) Subject: fs/resctrl: Add monitor property 'mbm_cntr_assign_fixed' X-Git-Url: http://git.ipfire.org/gitweb/index.cgi?a=commitdiff_plain;h=ee3d4c81d89c92fbeb65807971ac22b3dfa49220;p=thirdparty%2Fkernel%2Flinux.git fs/resctrl: Add monitor property 'mbm_cntr_assign_fixed' Commit 3b497c3f4f04 ("fs/resctrl: Introduce the interface to display monitoring modes") introduced CONFIG_RESCTRL_ASSIGN_FIXED but left adding the Kconfig entry until it was necessary. The counter assignment mode is fixed in MPAM, even when there are assignable counters, and so addressing this is needed to support MPAM. To avoid the burden of another Kconfig entry, replace CONFIG_RESCTRL_ASSIGN_FIXED with a new property in 'struct resctrl_mon', 'mbm_cntr_assign_fixed' to be set by the architecture. Do not request the architecture to change the counter assignment mode if it does not support doing so. Provide insight to user space about why such a request fails. Signed-off-by: Ben Horgan Signed-off-by: Borislav Petkov (AMD) Reviewed-by: Babu Moger Reviewed-by: Reinette Chatre Tested-by: Babu Moger Link: https://lore.kernel.org/20260506082855.3694761-1-ben.horgan@arm.com --- diff --git a/fs/resctrl/monitor.c b/fs/resctrl/monitor.c index 916f7a9d56581..5fbcc64e50ce7 100644 --- a/fs/resctrl/monitor.c +++ b/fs/resctrl/monitor.c @@ -1456,7 +1456,7 @@ int resctrl_mbm_assign_mode_show(struct kernfs_open_file *of, else seq_puts(s, "[default]\n"); - if (!IS_ENABLED(CONFIG_RESCTRL_ASSIGN_FIXED)) { + if (!r->mon.mbm_cntr_assign_fixed) { if (enabled) seq_puts(s, "default\n"); else @@ -1507,6 +1507,12 @@ ssize_t resctrl_mbm_assign_mode_write(struct kernfs_open_file *of, char *buf, } if (enable != resctrl_arch_mbm_cntr_assign_enabled(r)) { + if (r->mon.mbm_cntr_assign_fixed) { + ret = -EINVAL; + rdt_last_cmd_puts("Counter assignment mode is not configurable\n"); + goto out_unlock; + } + ret = resctrl_arch_mbm_cntr_assign_set(r, enable); if (ret) goto out_unlock; diff --git a/include/linux/resctrl.h b/include/linux/resctrl.h index 06e8c72e8660f..73ff522448a02 100644 --- a/include/linux/resctrl.h +++ b/include/linux/resctrl.h @@ -294,6 +294,7 @@ enum resctrl_schema_fmt { * @mbm_assign_on_mkdir: True if counters should automatically be assigned to MBM * events of monitor groups created via mkdir. * @mbm_cntr_configurable: True if assignable counters are configurable. + * @mbm_cntr_assign_fixed: True if the counter assignment mode is fixed. */ struct resctrl_mon { u32 num_rmid; @@ -302,6 +303,7 @@ struct resctrl_mon { bool mbm_cntr_assignable; bool mbm_assign_on_mkdir; bool mbm_cntr_configurable; + bool mbm_cntr_assign_fixed; }; /**