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The mode is enabled on a per-CPU basis, and kmode_cpus and kmode_cpus_list expose the CPUs used by active kernel mode. Add write support so userspace can update the CPUs used by the active kernel mode. Document the interface in Documentation/filesystems/resctrl.rst. Signed-off-by: Babu Moger --- v7: Changelog update. Last_cmd_status message update to keep the messages consistant. Minor changes to handle resctrl_kmode data structure changes. v6: Use flattened resctrl_kmode and global_enable_per_cpu. Fix the sashiko reported issue. https://sashiko.dev/#/patchset/cover.1787772750.git.babu.moger%40amd.com?part=15 Update the changelog. v5: Adapt to the resctrl_kcfg caps and active split. Use resctrl_kcfg.active.ctrl_mode and mon_mode in kmode_cpus_write(). Use full ctrl=/mon= syntax in the kmode_cpus example. v4: Empty masks are now allowed and updated masks are in rdtgroup->kmode_cpu_mask. Updated the changelog. v3: New patch to add "kmode_cpus" and "kmode_cpus_list" to support kernel_modes. --- Documentation/filesystems/resctrl.rst | 30 +++++++ fs/resctrl/rdtgroup.c | 114 +++++++++++++++++++++++++- 2 files changed, 142 insertions(+), 2 deletions(-) diff --git a/Documentation/filesystems/resctrl.rst b/Documentation/filesystems/resctrl.rst index 1a1877222624..2f0f6f01766f 100644 --- a/Documentation/filesystems/resctrl.rst +++ b/Documentation/filesystems/resctrl.rst @@ -716,6 +716,36 @@ All groups contain the following files: "cpus_list": Just like "cpus", only using ranges of CPUs instead of bitmasks. +"kmode_cpus": + Accessible only within the resource group backing the active global + per-CPU kernel mode (see "info/kernel_mode"). + + Bitmask of the logical CPUs used by resource group backing the kernel + mode. When kernel mode is activated through info/kernel_mode, every + currently online CPU is included. CPUs that come online later are + automatically added to the group. + + Writing a mask replaces the CPU mask. The mode is enabled on CPUs + added to the mask and disabled on CPUs removed from it. An empty mask + disables the mode on all currently online CPUs. CPUs that come online + later are still automatically added to the group. The mask must + contain only online CPUs; masks naming offline CPUs are rejected. + Errors are reported in "info/last_cmd_status". + Example:: + + # mkdir ctrl1 + # echo "global_enable_per_cpu:ctrl=assign;mon=assign;group=ctrl1//" \ + > info/kernel_mode + # echo 0-3 > ctrl1/kmode_cpus_list + # cat ctrl1/kmode_cpus + f + # cat ctrl1/kmode_cpus_list + 0-3 + +"kmode_cpus_list": + Just like "kmode_cpus", only using ranges of CPUs instead of bitmasks. + Writable with the same semantics and restrictions as "kmode_cpus". + When control is enabled all CTRL_MON groups will also contain: diff --git a/fs/resctrl/rdtgroup.c b/fs/resctrl/rdtgroup.c index 86bd6a66812b..0d67e7086e25 100644 --- a/fs/resctrl/rdtgroup.c +++ b/fs/resctrl/rdtgroup.c @@ -427,6 +427,114 @@ static void resctrl_configure_kmode_global(const struct cpumask *mask, enable); } +/** + * kmode_cpus_write() - Update @rdtgrp's kmode_cpu_mask from @newmask + * @rdtgrp: Resctrl group whose kmode_cpu_mask is being updated. + * @newmask: New CPUs for @rdtgrp's kernel mode association. + * @tmpmask: Caller-allocated scratch cpumask used to compute the + * incremental enable/disable deltas. + * + * Enable the kernel mode on CPUs added to the mask and disable it on + * CPUs removed from the mask. + */ +static void kmode_cpus_write(struct rdtgroup *rdtgrp, + cpumask_var_t newmask, cpumask_var_t tmpmask) +{ + /* CPUs dropped from this group: old & ~newmask. */ + cpumask_andnot(tmpmask, &rdtgrp->kmode_cpu_mask, newmask); + if (!cpumask_empty(tmpmask)) + resctrl_configure_kmode_global(tmpmask, rdtgrp, false); + + /* CPUs newly added: newmask & ~old. */ + cpumask_andnot(tmpmask, newmask, &rdtgrp->kmode_cpu_mask); + if (!cpumask_empty(tmpmask)) + resctrl_configure_kmode_global(tmpmask, rdtgrp, true); + + cpumask_copy(&rdtgrp->kmode_cpu_mask, newmask); +} + +/** + * rdtgroup_kmode_cpus_write() - Write kmode_cpus or kmode_cpus_list + * @of: kernfs open file + * @buf: CPU bitmask or list from userspace + * @nbytes: length of @buf + * @off: unused + * + * Update the CPU mask of the group that backs the kernel mode. + * + * Return: @nbytes on success, negative errno on error. + */ +static ssize_t rdtgroup_kmode_cpus_write(struct kernfs_open_file *of, + char *buf, size_t nbytes, loff_t off) +{ + cpumask_var_t tmpmask = CPUMASK_VAR_NULL, newmask = CPUMASK_VAR_NULL; + struct rdtgroup *rdtgrp; + int ret; + + rdtgrp = rdtgroup_kn_lock_live(of->kn); + if (!rdtgrp) { + ret = -ENOENT; + goto out_unlock; + } + + if (!buf) { + rdt_last_cmd_printf("%s: Invalid input\n", + is_cpu_list(of) ? "kmode_cpus_list" : + "kmode_cpus"); + ret = -EINVAL; + goto out_unlock; + } + + if (!zalloc_cpumask_var(&tmpmask, GFP_KERNEL) || + !zalloc_cpumask_var(&newmask, GFP_KERNEL)) { + rdt_last_cmd_printf("%s: Kernel allocation failure\n", + is_cpu_list(of) ? "kmode_cpus_list" : + "kmode_cpus"); + ret = -ENOMEM; + goto out_free; + } + + if (resctrl_kmode.active != RESCTRL_GLOBAL_ENABLE_PER_CPU) { + rdt_last_cmd_puts("No active global per-cpu kernel mode\n"); + ret = -EINVAL; + goto out_free; + } + + if (resctrl_kmode.rdtgrp != rdtgrp) { + rdt_last_cmd_puts("Group is not backing the global per-cpu kernel mode\n"); + ret = -EINVAL; + goto out_free; + } + + if (is_cpu_list(of)) + ret = cpulist_parse(buf, newmask); + else + ret = cpumask_parse(buf, newmask); + + if (ret) { + rdt_last_cmd_puts("Bad CPU list/mask\n"); + goto out_free; + } + + /* kernel-mode association is only programmed on online CPUs. */ + cpumask_andnot(tmpmask, newmask, cpu_online_mask); + if (!cpumask_empty(tmpmask)) { + rdt_last_cmd_puts("Can only assign online CPUs\n"); + ret = -EINVAL; + goto out_free; + } + + kmode_cpus_write(rdtgrp, newmask, tmpmask); + +out_free: + free_cpumask_var(tmpmask); + free_cpumask_var(newmask); +out_unlock: + rdtgroup_kn_unlock(of->kn); + + return ret ?: nbytes; +} + /* * Update the PGR_ASSOC MSR on all cpus in @cpu_mask, * @@ -2689,17 +2797,19 @@ static struct rftype res_common_files[] = { }, { .name = "kmode_cpus", - .mode = 0444, + .mode = 0644, .hidden = true, .kf_ops = &rdtgroup_kf_single_ops, + .write = rdtgroup_kmode_cpus_write, .seq_show = rdtgroup_kmode_cpus_show, .fflags = RFTYPE_BASE, }, { .name = "kmode_cpus_list", - .mode = 0444, + .mode = 0644, .hidden = true, .kf_ops = &rdtgroup_kf_single_ops, + .write = rdtgroup_kmode_cpus_write, .seq_show = rdtgroup_kmode_cpus_show, .flags = RFTYPE_FLAGS_CPUS_LIST, .fflags = RFTYPE_BASE, -- 2.43.0