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SubjectRE: [PATCH v9 08/13] x86/resctrl: Add sysfs interface to read mbm_total_bytes_config
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[AMD Official Use Only - General]

Hi Reinette,

> -----Original Message-----
> From: Reinette Chatre <reinette.chatre@intel.com>
> Sent: Thursday, December 15, 2022 11:41 AM
> To: Moger, Babu <Babu.Moger@amd.com>; corbet@lwn.net;
> tglx@linutronix.de; mingo@redhat.com; bp@alien8.de
> Cc: fenghua.yu@intel.com; dave.hansen@linux.intel.com; x86@kernel.org;
> hpa@zytor.com; paulmck@kernel.org; akpm@linux-foundation.org;
> quic_neeraju@quicinc.com; rdunlap@infradead.org;
> damien.lemoal@opensource.wdc.com; songmuchun@bytedance.com;
> peterz@infradead.org; jpoimboe@kernel.org; pbonzini@redhat.com;
> chang.seok.bae@intel.com; pawan.kumar.gupta@linux.intel.com;
> jmattson@google.com; daniel.sneddon@linux.intel.com; Das1, Sandipan
> <Sandipan.Das@amd.com>; tony.luck@intel.com; james.morse@arm.com;
> linux-doc@vger.kernel.org; linux-kernel@vger.kernel.org;
> bagasdotme@gmail.com; eranian@google.com; christophe.leroy@csgroup.eu;
> jarkko@kernel.org; adrian.hunter@intel.com; quic_jiles@quicinc.com;
> peternewman@google.com
> Subject: Re: [PATCH v9 08/13] x86/resctrl: Add sysfs interface to read
> mbm_total_bytes_config
>
> Hi Babu,
>
> I would like to second James's suggestion to replace sysfs with resctrl or just
> remove it. I am concerned that you mentioned in recent message that you only
> plan changes to patch 10 while James highlighted that this needs to be
> addressed in entire series. Could you please ensure that you check all the
> patches?

Ok. Sure. Will remove it.
x86/resctrl: Add interface to write mbm_total_bytes_config

Will check other patches for similar changes.

>
> On 12/1/2022 7:36 AM, Babu Moger wrote:
> > The current event configuration can be viewed by the user by reading
>
> What "current" means is not clear and the term could just be removed.

Will remove it.
>
> > the configuration file /sys/fs/resctrl/info/L3_MON/mbm_total_bytes_config.
> > The event configuration settings are domain specific and will affect
> > all the CPUs in the domain.
> >
> > Following are the types of events supported:
> > ====
> ===========================================================
> > Bits Description
> > ====
> ===========================================================
> > 6 Dirty Victims from the QOS domain to all types of memory
> > 5 Reads to slow memory in the non-local NUMA domain
> > 4 Reads to slow memory in the local NUMA domain
> > 3 Non-temporal writes to non-local NUMA domain
> > 2 Non-temporal writes to local NUMA domain
> > 1 Reads to memory in the non-local NUMA domain
> > 0 Reads to memory in the local NUMA domain
> > ====
> ===========================================================
> >
> > By default, the mbm_total_bytes_config is set to 0x7f to count all the
> > event types.
> >
> > For example:
> > $cat /sys/fs/resctrl/info/L3_MON/mbm_total_bytes_config
> > 0=0x7f;1=0x7f;2=0x7f;3=0x7f
> >
> > In this case, the event mbm_total_bytes is currently configured
> > with 0x7f on domains 0 to 3.
>
> "currently" can be removed since it already starts with "In this case".

Sure.
>
>
> > Signed-off-by: Babu Moger <babu.moger@amd.com>
> > ---
> > arch/x86/include/asm/msr-index.h | 1
> > arch/x86/kernel/cpu/resctrl/internal.h | 24 ++++++++
> > arch/x86/kernel/cpu/resctrl/monitor.c | 4 +
> > arch/x86/kernel/cpu/resctrl/rdtgroup.c | 99
> ++++++++++++++++++++++++++++++++
> > 4 files changed, 127 insertions(+), 1 deletion(-)
> >
>
> ...
>
> > diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> > b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> > index 8342feb54a7f..e93b1c206116 100644
> > --- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> > +++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> > @@ -1423,6 +1423,90 @@ static int rdtgroup_size_show(struct
> kernfs_open_file *of,
> > return ret;
> > }
> >
> > +struct mon_config_info {
> > + u32 evtid;
> > + u32 mon_config;
> > +};
> > +
> > +#define INVALID_CONFIG_INDEX UINT_MAX
> > +
> > +/**
> > + * mon_event_config_index_get - get the index for the configurable
> > +event
>
> Could you say "get the hardware index" to help clarify what the index is for?

Sure.

>
> > + * @evtid: event id.
> > + *
> > + * Return: 0 for evtid == QOS_L3_MBM_TOTAL_EVENT_ID
> > + * 1 for evtid == QOS_L3_MBM_LOCAL_EVENT_ID
> > + * INVALID_CONFIG_INDEX for invalid evtid
> > + */
> > +static inline unsigned int mon_event_config_index_get(u32 evtid) {
> > + switch (evtid) {
> > + case QOS_L3_MBM_TOTAL_EVENT_ID:
> > + return 0;
> > + case QOS_L3_MBM_LOCAL_EVENT_ID:
> > + return 1;
> > + default:
> > + /* WARN */
> > + return INVALID_CONFIG_INDEX;
> > + }
> > +}
>
> I see that you copied my sample code here. My intention was that the
> /* WARN */ comment be replaced with an actual warning. As a comment it
> does not add value. Since the caller now prints a subtler warning it could just
> be:
>
> /* Should never reach here */
> return INVALID_CONFIG_INDEX;

Sure.
>
> > +
> > +static void mon_event_config_read(void *info) {
> > + struct mon_config_info *mon_info = info;
> > + u32 h, index;
>
> index can be "unsigned int" as returned by mon_event_config_index_get()

Ok. Sure

>
> > +
> > + index = mon_event_config_index_get(mon_info->evtid);
> > + if (index == INVALID_CONFIG_INDEX) {
> > + pr_warn_once("Invalid event id %d\n", mon_info->evtid);
> > + return;
> > + }
> > + rdmsr(MSR_IA32_EVT_CFG_BASE + index, mon_info->mon_config, h);
> > +
> > + /* Report only the valid event configuration bits */
> > + mon_info->mon_config &= MAX_EVT_CONFIG_BITS; }
> > +
> > +static void mondata_config_read(struct rdt_domain *d, struct
> > +mon_config_info *mon_info) {
> > + smp_call_function_any(&d->cpu_mask, mon_event_config_read,
> mon_info,
> > +1); }
> > +
> > +static int mbm_config_show(struct seq_file *s, struct rdt_resource
> > +*r, u32 evtid) {
> > + struct mon_config_info mon_info = {0};
> > + struct rdt_domain *dom;
> > + bool sep = false;
> > +
> > + mutex_lock(&rdtgroup_mutex);
> > +
> > + list_for_each_entry(dom, &r->domains, list) {
> > + if (sep)
> > + seq_puts(s, ";");
> > +
> > + mon_info.evtid = evtid;
> > + mondata_config_read(dom, &mon_info);
> > +
>
> For robustness, please reset mon_config before calling mondata_config_read().
> Since
> mon_event_config_read() may (yes this is very unlikely) exit early then
> mon_config will contain the data from the previous domain.

Sure. I can call memset to reset.
Thanks
Babu

>
> > + seq_printf(s, "%d=0x%02x", dom->id, mon_info.mon_config);
> > + sep = true;
> > + }
> > + seq_puts(s, "\n");
> > +
> > + mutex_unlock(&rdtgroup_mutex);
> > +
> > + return 0;
> > +}
> > +
>
> ...
>
> Reinette
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