Re: [PATCH v5 06/20] x86/resctrl: Add support to enable/disable AMD ABMC feature

["Moger, Babu" <babu.moger@amd.com>]

Hi Reinette,

On 7/16/24 12:51, Reinette Chatre wrote:
> Hi Babu,
> 
> On 7/16/24 8:13 AM, Moger, Babu wrote:
>> On 7/12/24 17:05, Reinette Chatre wrote:
>>> On 7/3/24 2:48 PM, Babu Moger wrote:
>>>> Add the functionality to enable/disable AMD ABMC feature.
>>>>
>>>> AMD ABMC feature is enabled by setting enabled bit(0) in MSR
>>>> L3_QOS_EXT_CFG.  When the state of ABMC is changed, the MSR needs
>>>> to be updated on all the logical processors in the QOS Domain.
>>>>
>>>> Hardware counters will reset when ABMC state is changed. Reset the
>>>> architectural state so that reading of hardware counter is not considered
>>>> as an overflow in next update.
>>>>
>>>> The ABMC feature details are documented in APM listed below [1].
>>>> [1] AMD64 Architecture Programmer's Manual Volume 2: System Programming
>>>> Publication # 24593 Revision 3.41 section 19.3.3.3 Assignable Bandwidth
>>>> Monitoring (ABMC).
>>>>
>>>> Signed-off-by: Babu Moger <babu.moger@amd.com>
>>>> Link: https://bugzilla.kernel.org/show_bug.cgi?id=206537
>>>> ---
>>>> v5: Renamed resctrl_abmc_enable to resctrl_arch_abmc_enable.
>>>>       Renamed resctrl_abmc_disable to resctrl_arch_abmc_disable.
>>>>       Introduced resctrl_arch_get_abmc_enabled to get abmc state from
>>>>       non-arch code.
>>>>       Renamed resctrl_abmc_set_all to _resctrl_abmc_enable().
>>>>       Modified commit log to make it clear about AMD ABMC feature.
>>>>
>>>> v3: No changes.
>>>>
>>>> v2: Few text changes in commit message.
>>>> ---
>>>>    arch/x86/include/asm/msr-index.h       |  1 +
>>>>    arch/x86/kernel/cpu/resctrl/internal.h | 13 +++++
>>>>    arch/x86/kernel/cpu/resctrl/rdtgroup.c | 66 ++++++++++++++++++++++++++
>>>>    3 files changed, 80 insertions(+)
>>>>
>>>> diff --git a/arch/x86/include/asm/msr-index.h
>>>> b/arch/x86/include/asm/msr-index.h
>>>> index 01342963011e..263b2d9d00ed 100644
>>>> --- a/arch/x86/include/asm/msr-index.h
>>>> +++ b/arch/x86/include/asm/msr-index.h
>>>> @@ -1174,6 +1174,7 @@
>>>>    #define MSR_IA32_MBA_BW_BASE        0xc0000200
>>>>    #define MSR_IA32_SMBA_BW_BASE        0xc0000280
>>>>    #define MSR_IA32_EVT_CFG_BASE        0xc0000400
>>>> +#define MSR_IA32_L3_QOS_EXT_CFG        0xc00003ff
>>>>      /* MSR_IA32_VMX_MISC bits */
>>>>    #define MSR_IA32_VMX_MISC_INTEL_PT                 (1ULL << 14)
>>>> diff --git a/arch/x86/kernel/cpu/resctrl/internal.h
>>>> b/arch/x86/kernel/cpu/resctrl/internal.h
>>>> index 2bd207624eec..0ce9797f80fe 100644
>>>> --- a/arch/x86/kernel/cpu/resctrl/internal.h
>>>> +++ b/arch/x86/kernel/cpu/resctrl/internal.h
>>>> @@ -97,6 +97,9 @@ cpumask_any_housekeeping(const struct cpumask *mask,
>>>> int exclude_cpu)
>>>>        return cpu;
>>>>    }
>>>>    +/* Setting bit 0 in L3_QOS_EXT_CFG enables the ABMC feature */
>>>
>>> Please be consistent throughout series to have sentences end with period.
>>
>> Sure.
>>
>>>
>>>> +#define ABMC_ENABLE            BIT(0)
>>>> +
>>>>    struct rdt_fs_context {
>>>>        struct kernfs_fs_context    kfc;
>>>>        bool                enable_cdpl2;
>>>> @@ -477,6 +480,7 @@ struct rdt_parse_data {
>>>>     * @mbm_cfg_mask:    Bandwidth sources that can be tracked when
>>>> Bandwidth
>>>>     *            Monitoring Event Configuration (BMEC) is supported.
>>>>     * @cdp_enabled:    CDP state of this resource
>>>> + * @abmc_enabled:    ABMC feature is enabled
>>>>     *
>>>>     * Members of this structure are either private to the architecture
>>>>     * e.g. mbm_width, or accessed via helpers that provide
>>>> abstraction. e.g.
>>>> @@ -491,6 +495,7 @@ struct rdt_hw_resource {
>>>>        unsigned int        mbm_width;
>>>>        unsigned int        mbm_cfg_mask;
>>>>        bool            cdp_enabled;
>>>> +    bool            abmc_enabled;
>>>>    };
>>>
>>> mbm_cntr_enabled? This is architecture specific code so there is more
>>> flexibility
>>> here, but it may make implementation easier to understand if consistent
>>> naming is used
>>> between fs and arch code.
>>
>> How about "mbm_cntr_assign_enabled" or "cntr_assign_enabled" ?
> 
> My preference is to keep the term "mbm_cntr" to be consistent with the
> other variables/struct members to help when reading the code.
> "mbm_cntr_assign_enabled" does seem to be getting long though.
> Are you planning to use it by assigning it to a local variable with shorter
> name?

Yes. We can do that.

> 
> As a sidenote, I will be offline for large portions of the next few weeks
> and thus unresponsive during this time. I'll be back to a regular
> schedule on August 12th.

Thanks for the heads up.
Thanks
Babu Moger