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>>>> cpuid_count(0x80000020, 5, &eax, &ebx, &ecx, &edx); >>>> r->mon.num_mbm_cntrs = (ebx & GENMASK(15, 0)) + 1; >>> >>>> + hw_res->mbm_cntr_assign_enabled = true; >>> >>> Here the arch code sets ABMC to be enabled by default at boot. >>> >>> >>>> diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c >>>> index 6922173c4f8f..515969c5f64f 100644 >>>> --- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c >>>> +++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c >>>> @@ -4302,9 +4302,13 @@ int resctrl_online_mon_domain(struct rdt_resource *r, struct rdt_mon_domain *d) >>>> >>>> void resctrl_online_cpu(unsigned int cpu) >>>> { >>>> + struct rdt_resource *r = &rdt_resources_all[RDT_RESOURCE_L3].r_resctrl; >>>> + >>>> mutex_lock(&rdtgroup_mutex); >>>> /* The CPU is set in default rdtgroup after online. */ >>>> cpumask_set_cpu(cpu, &rdtgroup_default.cpu_mask); >>>> + if (r->mon_capable && r->mon.mbm_cntr_assignable) >>>> + resctrl_arch_mbm_cntr_assign_set_one(r); >>>> mutex_unlock(&rdtgroup_mutex); >>>> } >>> >>> But here, resctrl has to call back to the arch code to make sure the hardware is in the >>> same state as hw_res->mbm_cntr_assign_enabled. > > Another scenario needing to be supported by this flow is when CPUs come online later ... > after resctrl is mounted and potentially after the user modified the assignable counter > mode. If the user modifies the assignable counter mode. It is recorded in mbm_cntr_assign_enabled already. When the new CPU comes online, the hotplug handler(resctrl_arch_online_cpu) is will update the CPU to the new mode after checking mbm_cntr_assign_enabled. Are you talking about different case here? Please elaborate. > >>> >>> Could this be done in resctrl_arch_online_cpu() instead? That way resctrl doesn't get CPUs >>> in an inconsistent state that it has to fix up... > > Could you please elaborate the inconsistent state that would need to be fixed up? > >>> >> >> Sure. Here is the diff. >> >> diff --git a/arch/x86/kernel/cpu/resctrl/core.c >> b/arch/x86/kernel/cpu/resctrl/core.c >> index 22399f19810f..f48b298413bc 100644 >> --- a/arch/x86/kernel/cpu/resctrl/core.c >> +++ b/arch/x86/kernel/cpu/resctrl/core.c >> @@ -771,6 +771,12 @@ static int resctrl_arch_online_cpu(unsigned int cpu) >> domain_add_cpu(cpu, r); >> mutex_unlock(&domain_list_lock); >> >> + r = &rdt_resources_all[RDT_RESOURCE_L3].r_resctrl; >> + mutex_lock(&rdtgroup_mutex); >> + if (r->mon_capable && r->mon.mbm_cntr_assignable) >> + resctrl_arch_mbm_cntr_assign_set_one(r); >> + mutex_unlock(&rdtgroup_mutex); >> + >> clear_closid_rmid(cpu); >> resctrl_online_cpu(cpu); > > This would require every architecture to duplicate the above, no? > > Also, please note there is more appropriate domain_add_cpu_mon(). Yes. This may be better place to add this code. Will wait once James clarifies on "inconsistent state". -- Thanks Babu Moger