Re: [PATCH v5 18/20] x86/resctrl: Enable AMD ABMC feature by default when supported

["Moger, Babu" <bmoger@xxxxxxx>]

Hi Reinette,

On 7/16/2024 6:23 PM, Moger, Babu wrote:
> Hi Reinette,
>
> On 7/12/2024 5:15 PM, Reinette Chatre wrote:
> > Hi Babu,
> >
> > On 7/3/24 2:48 PM, Babu Moger wrote:
> > > Enable ABMC by default when supported during the boot up.
> > >
> > > Users will not see any difference in the behavior when resctrl is
> > > mounted. With automatic assignment everything will work as running
> > > in the legacy monitor mode.
> > >
> > > Signed-off-by: Babu Moger <babu.moger@xxxxxxx>
> > > ---
> > > v5: New patch to enable ABMC by default.
> > > ---
> > >   arch/x86/kernel/cpu/resctrl/core.c     |  2 ++
> > >   arch/x86/kernel/cpu/resctrl/internal.h |  1 +
> > >   arch/x86/kernel/cpu/resctrl/rdtgroup.c | 17 +++++++++++++++++
> > >   3 files changed, 20 insertions(+)
> > >
> > > diff --git a/arch/x86/kernel/cpu/resctrl/core.c 
> > > b/arch/x86/kernel/cpu/resctrl/core.c
> > > index 6265ef8b610f..b69b2650bde3 100644
> > > --- a/arch/x86/kernel/cpu/resctrl/core.c
> > > +++ b/arch/x86/kernel/cpu/resctrl/core.c
> > > @@ -599,6 +599,7 @@ static void domain_add_cpu_mon(int cpu, struct 
> > > rdt_resource *r)
> > >           d = container_of(hdr, struct rdt_mon_domain, hdr);
> > >           cpumask_set_cpu(cpu, &d->hdr.cpu_mask);
> > > +        resctrl_arch_configure_abmc();
> > >           return;
> > >       }
> > > @@ -620,6 +621,7 @@ static void domain_add_cpu_mon(int cpu, struct 
> > > rdt_resource *r)
> > >       arch_mon_domain_online(r, d);
> > >       resctrl_arch_mbm_evt_config(hw_dom);
> > > +    resctrl_arch_configure_abmc();
> > >       if (arch_domain_mbm_alloc(r->mon.num_rmid, hw_dom)) {
> > >           mon_domain_free(hw_dom);
> > > diff --git a/arch/x86/kernel/cpu/resctrl/internal.h 
> > > b/arch/x86/kernel/cpu/resctrl/internal.h
> > > index beb005775fe4..0f858cff8ab1 100644
> > > --- a/arch/x86/kernel/cpu/resctrl/internal.h
> > > +++ b/arch/x86/kernel/cpu/resctrl/internal.h
> > > @@ -707,6 +707,7 @@ void rdt_domain_reconfigure_cdp(struct 
> > > rdt_resource *r);
> > >   void __init resctrl_file_fflags_init(const char *config,
> > >                        unsigned long fflags);
> > >   void resctrl_arch_mbm_evt_config(struct rdt_hw_mon_domain *hw_dom);
> > > +void resctrl_arch_configure_abmc(void);
> > >   unsigned int mon_event_config_index_get(u32 evtid);
> > >   int resctrl_arch_assign_cntr(struct rdt_mon_domain *d, u32 evtid, 
> > > u32 rmid,
> > >                    u32 cntr_id, u32 closid, bool enable);
> > > diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c 
> > > b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> > > index 531233779f8d..d978668c8865 100644
> > > --- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> > > +++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> > > @@ -2733,6 +2733,23 @@ void resctrl_arch_abmc_disable(void)
> > >       }
> > >   }
> > > +void resctrl_arch_configure_abmc(void)
> > > +{
> > > +    struct rdt_resource *r = 
> > > &rdt_resources_all[RDT_RESOURCE_L3].r_resctrl;
> > > +    struct rdt_hw_resource *hw_res = resctrl_to_arch_res(r);
> > > +    bool enable = true;
> > > +
> > > +    mutex_lock(&rdtgroup_mutex);
> > > +
> > > +    if (r->mon.abmc_capable) {
> > > +        if (!hw_res->abmc_enabled)
> > > +            hw_res->abmc_enabled = true;
> > > +        resctrl_abmc_set_one_amd(&enable);
> > > +    }
> >
> > This does not look right. It is not architecture code that needs to
> > decide if this feature is enabled or not, right? The feature is enabled
> > via fs (for example when user writes to mbm_mode). If the default is
> > enabled then it should be set by fs. resctrl_arch_configure_abmc()
> > then checks if feature is capable and enabled before it configures
> > it on the CPU.

Looking at the code again, I think it is fine to do it here. This is 
arch initialization code. I am checking if the feature is available and 
enable it by default. The fs code is not initialized yet at this stage.

Other option is to move everything to rdt_enable_ctx which is during the 
mount time.

I will keep it as is now. We can discuss more on this in v6.

> That is correct. But this is a default setting should be done during the 
> initialization. This is like rdtgroup_setup_default(). I can move this 
> inside rdtgroup_init(void). I will have to change few things make sure 
> arch and fs code separate (like accessing abmc_enabled).
> Thanks
> - Babu Moger

--
- Babu Moger