Hi Babu,
On 8/22/2022 6:43 AM, Babu Moger wrote:
> Newer AMD processors support the new feature Bandwidth Monitoring Event
> Configuration (BMEC). The events mbm_total_bytes and mbm_local_bytes
> are configurable when this feature is present.
>
> Set mon_configurable if the feature is available.
>
> Signed-off-by: Babu Moger <babu.moger@xxxxxxx>
> Reviewed-by: Ingo Molnar <mingo@xxxxxxxxxx>
> ---
> arch/x86/kernel/cpu/resctrl/monitor.c | 14 ++++++++++++++
> arch/x86/kernel/cpu/resctrl/rdtgroup.c | 17 +++++++++++++++++
> include/linux/resctrl.h | 1 +
> 3 files changed, 32 insertions(+)
>
> diff --git a/arch/x86/kernel/cpu/resctrl/monitor.c b/arch/x86/kernel/cpu/resctrl/monitor.c
> index eaf25a234ff5..b9de417dac1c 100644
> --- a/arch/x86/kernel/cpu/resctrl/monitor.c
> +++ b/arch/x86/kernel/cpu/resctrl/monitor.c
> @@ -682,6 +682,16 @@ static void l3_mon_evt_init(struct rdt_resource *r)
> list_add_tail(&mbm_local_event.list, &r->evt_list);
> }
>
> +
> +void __rdt_get_mon_l3_config_amd(struct rdt_resource *r)
> +{
> + /*
> + * Check if CPU supports the Bandwidth Monitoring Event Configuration
> + */
> + if (boot_cpu_has(X86_FEATURE_BMEC))
> + r->mon_configurable = true;
> +}
Could this rather use rdt_cpu_has() with the added support for disabling
the feature via kernel parameter?
> +
> int rdt_get_mon_l3_config(struct rdt_resource *r)
> {
> unsigned int mbm_offset = boot_cpu_data.x86_cache_mbm_width_offset;
> @@ -714,6 +724,10 @@ int rdt_get_mon_l3_config(struct rdt_resource *r)
> if (ret)
> return ret;
>
> + if (boot_cpu_data.x86_vendor == X86_VENDOR_AMD)
> + __rdt_get_mon_l3_config_amd(r);
> +
> +
Why is this vendor check needed? Is X86_FEATURE_BMEC not sufficient?
> l3_mon_evt_init(r);
>
> r->mon_capable = true;
> diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> index fc5286067201..855483b297a8 100644
> --- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> +++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> @@ -995,6 +995,16 @@ static int rdt_num_rmids_show(struct kernfs_open_file *of,
> return 0;
> }
>
> +static int rdt_mon_configurable_show(struct kernfs_open_file *of,
> + struct seq_file *seq, void *v)
> +{
> + struct rdt_resource *r = of->kn->parent->priv;
> +
> + seq_printf(seq, "%d\n", r->mon_configurable);
Why is this file needed? It seems that the next patches also introduce
files in support of this new feature that will make the actual configuration
data accessible - those files are only created if this feature is supported.
Would those files not be sufficient for user space to learn about the feature
support?
Reinette
