Hi Reinette,
On 6/13/24 20:51, Reinette Chatre wrote:
> Hi Babu,
>
> On 5/24/24 5:23 AM, Babu Moger wrote:
>> Introduce interface to switch between ABMC and legacy_mbm modes.
>
> shortlog and first sentence of changelog do not match: mbm_legacy vs
> legacy_mbm?
Will correct it.
>
>>
>> By default ABMC is enabled on resctrl mount if the feature is available.
>> However, user will have the option to go back to legacy_mbm if required.
>>
>> $ cat /sys/fs/resctrl/info/L3_MON/mbm_assign
>> [abmc]
>> mbm_legacy
>>
>> To enable the legacy monitoring feature:
>> $ echo "mbm_legacy" > /sys/fs/resctrl/info/L3_MON/mbm_assign
>
> Missing information about user visible impact to counters/events
> and any mitigations needed in implementation.
Sure. Will add the details.
>
>>
>> Signed-off-by: Babu Moger <babu.moger@amd.com>
>> ---
>> v4: Minor commit text changes. Keep the default to ABMC when supported.
>>
>> v3: New patch to address the review comments from upstream.
>> ---
>> Documentation/arch/x86/resctrl.rst | 10 +++++++
>> arch/x86/kernel/cpu/resctrl/rdtgroup.c | 40 +++++++++++++++++++++++++-
>> 2 files changed, 49 insertions(+), 1 deletion(-)
>>
>> diff --git a/Documentation/arch/x86/resctrl.rst
>> b/Documentation/arch/x86/resctrl.rst
>> index ab3cde61a124..fd050d4d22cd 100644
>> --- a/Documentation/arch/x86/resctrl.rst
>> +++ b/Documentation/arch/x86/resctrl.rst
>> @@ -271,6 +271,16 @@ with the following files:
>> [abmc]
>> mbm_legacy
>> + * To enable ABMC feature:
>> + ::
>> +
>> + # echo "abmc" > /sys/fs/resctrl/info/L3_MON/mbm_assign
>> +
>> + * To enable the legacy monitoring feature:
>> + ::
>> +
>> + # echo "mbm_legacy" > /sys/fs/resctrl/info/L3_MON/mbm_assign
>> +
>
> No information about what the features are or what will happen on such a
> switch.
Ok. Sure. Will add more documentation.
>
>> "max_threshold_occupancy":
>> Read/write file provides the largest value (in
>> bytes) at which a previously used LLC_occupancy
>> diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
>> b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
>> index f452b6d9bb99..d77ff059269a 100644
>> --- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
>> +++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
>> @@ -908,6 +908,43 @@ static int rdtgroup_mbm_assign_show(struct
>> kernfs_open_file *of,
>> return 0;
>> }
>> +/*
>> + * rdtgroup_mode_write - Modify the resource group's mode
>
> Comment does not match function name. Seems like "mode" is the generic term
> to use instead of "assign".
Sure. Will fix.
>
>> + */
>> +static ssize_t rdtgroup_mbm_assign_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;
>> +
>> + if (!r->abmc_capable)
>> + return -EINVAL;
>> +
>> + /* 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, "mbm_legacy"))
>> + resctrl_abmc_disable(RDT_RESOURCE_L3);
>> + else if (!strcmp(buf, "abmc"))
>> + ret = resctrl_abmc_enable(RDT_RESOURCE_L3);
>> + else
>> + ret = -EINVAL;
>> +
>> + mutex_unlock(&rdtgroup_mutex);
>> + cpus_read_unlock();
>> +
>> + return ret ?: nbytes;
>> +}
>> +
>> #ifdef CONFIG_PROC_CPU_RESCTRL
>> /*
>> @@ -2087,9 +2124,10 @@ static struct rftype res_common_files[] = {
>> },
>> {
>> .name = "mbm_assign",
>> - .mode = 0444,
>> + .mode = 0644,
>> .kf_ops = &rdtgroup_kf_single_ops,
>> .seq_show = rdtgroup_mbm_assign_show,
>> + .write = rdtgroup_mbm_assign_write,
>> },
>> {
>> .name = "cpus",
>
>
> Reinette
>
--
Thanks
Babu Moger