Hi Babu, On 10/9/24 10:39 AM, Babu Moger wrote: > Introduce interface to switch between mbm_cntr_assign and default modes. > > $ cat /sys/fs/resctrl/info/L3_MON/mbm_assign_mode > [mbm_cntr_assign] > default > > To enable the "mbm_cntr_assign" mode: > $ echo "mbm_cntr_assign" > /sys/fs/resctrl/info/L3_MON/mbm_assign_mode > > To enable the default monitoring mode: > $ echo "default" > /sys/fs/resctrl/info/L3_MON/mbm_assign_mode > > MBM event counters will reset when mbm_assign_mode is changed. > > Signed-off-by: Babu Moger <babu.moger@xxxxxxx> > --- ... > --- > Documentation/arch/x86/resctrl.rst | 15 ++++++ > arch/x86/kernel/cpu/resctrl/rdtgroup.c | 75 +++++++++++++++++++++++++- > 2 files changed, 89 insertions(+), 1 deletion(-) > > diff --git a/Documentation/arch/x86/resctrl.rst b/Documentation/arch/x86/resctrl.rst > index 99ee9c87952b..d9574078f735 100644 > --- a/Documentation/arch/x86/resctrl.rst > +++ b/Documentation/arch/x86/resctrl.rst > @@ -291,6 +291,21 @@ with the following files: > that case reading the mbm_total_bytes and mbm_local_bytes may report > 'Unavailable' if there is no counter associated with that group. > > + * To enable "mbm_cntr_assign" mode: > + :: > + > + # echo "mbm_cntr_assign" > /sys/fs/resctrl/info/L3_MON/mbm_assign_mode extra spaces > + > + * To enable default monitoring mode: > + :: > + > + # echo "default" > /sys/fs/resctrl/info/L3_MON/mbm_assign_mode extra spaces > + > + The MBM events (mbm_total_bytes and/or mbm_local_bytes) associated counters I did ask you not to copy the text verbatim https://lore.kernel.org/all/b38c93bf-4650-45d1-9aca-8b4c4d425886@xxxxxxxxx/ > + may reset when the mode is changed. Moving to mbm_cntr_assign mode will > + require users to assign the counters to the events. Otherwise, the MBM "will require" -> "require" > + event counters will return "Unassigned" when read. > + > "num_mbm_cntrs": > The number of monitoring counters available for assignment when the > architecture supports mbm_cntr_assign mode. > diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c > index cb2c60c0319e..88eda3cf5c82 100644 > --- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c > +++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c > @@ -888,6 +888,78 @@ static int rdtgroup_mbm_assign_mode_show(struct kernfs_open_file *of, > return 0; > } > > +static void mbm_cntr_reset(struct rdt_resource *r) > +{ > + struct rdtgroup *prgrp, *crgrp; > + struct rdt_mon_domain *dom; > + > + /* > + * Hardware counters will reset after switching the monitor mode. > + * Reset the architectural state so that reading of hardware > + * counter is not considered as an overflow in the next update. > + * Also reset the domain counter bitmap. > + */ > + list_for_each_entry(dom, &r->mon_domains, hdr.list) { > + bitmap_zero(dom->mbm_cntr_map, r->mon.num_mbm_cntrs); > + resctrl_arch_reset_rmid_all(r, dom); > + } > + > + /* Reset global MBM counter map */ > + bitmap_fill(r->mon.mbm_cntr_free_map, r->mon.num_mbm_cntrs); > + > + /* Reset the cntr_id's for all the monitor groups */ > + list_for_each_entry(prgrp, &rdt_all_groups, rdtgroup_list) { > + prgrp->mon.cntr_id[0] = MON_CNTR_UNSET; > + prgrp->mon.cntr_id[1] = MON_CNTR_UNSET; > + list_for_each_entry(crgrp, &prgrp->mon.crdtgrp_list, > + mon.crdtgrp_list) { > + crgrp->mon.cntr_id[0] = MON_CNTR_UNSET; > + crgrp->mon.cntr_id[1] = MON_CNTR_UNSET; > + } Please use MBM_EVENT_ARRAY_INDEX > + } > +} > + > +static ssize_t rdtgroup_mbm_assign_mode_write(struct kernfs_open_file *of, > + char *buf, size_t nbytes, loff_t off) > +{ > + struct rdt_resource *r = of->kn->parent->priv; > + int ret = 0; > + bool enable; > + > + /* Valid input requires a trailing newline */ > + if (nbytes == 0 || buf[nbytes - 1] != '\n') > + return -EINVAL; > + > + buf[nbytes - 1] = '\0'; > + > + cpus_read_lock(); > + mutex_lock(&rdtgroup_mutex); > + > + rdt_last_cmd_clear(); > + > + if (!strcmp(buf, "default")) { > + enable = 0; > + } else if (!strcmp(buf, "mbm_cntr_assign")) { > + enable = 1; > + } else { > + ret = -EINVAL; > + rdt_last_cmd_puts("Unsupported assign mode\n"); > + goto write_exit; > + } Please keep two things in mind: * this file is always accessible, whether platform supports assignable counters or not. * this is resctrl fs code. So, considering above, how should user interpret the "Unsupported assign mode"? Shouldn't it also return this error if a user attempts to enable "mbm_cntr_assign" on a platform that does not support this mode? > + > + if (enable != resctrl_arch_mbm_cntr_assign_enabled(r)) { resctrl_arch_mbm_cntr_assign_enabled() returns true if mbm_cntr_assign mode is enabled, but when it returns false it could mean different things: platform supports mbm_cntr_assign mode, but it is disabled, or platform does not support mbm_cntr_assign mode. resctrl fs should not rely on all archs to duplicate the all the checking done in resctrl_arch_mbm_cntr_assign_set(). It should never ask arch to enable a mode that it knows the platform is not capable of. > + ret = resctrl_arch_mbm_cntr_assign_set(r, enable); > + if (!ret) > + mbm_cntr_reset(r); > + } > + > +write_exit: > + mutex_unlock(&rdtgroup_mutex); > + cpus_read_unlock(); > + > + return ret ?: nbytes; > +} > + > static int rdtgroup_num_mbm_cntrs_show(struct kernfs_open_file *of, > struct seq_file *s, void *v) > { > @@ -2115,9 +2187,10 @@ static struct rftype res_common_files[] = { > }, > { > .name = "mbm_assign_mode", > - .mode = 0444, > + .mode = 0644, > .kf_ops = &rdtgroup_kf_single_ops, > .seq_show = rdtgroup_mbm_assign_mode_show, > + .write = rdtgroup_mbm_assign_mode_write, > .fflags = RFTYPE_MON_INFO, > }, > { Reinette
