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Message-ID: <95b0ee31-8746-474f-a15b-91c893fdce28@amd.com>
Date: Thu, 16 May 2024 15:03:33 -0500
From: "Moger, Babu" <babu.moger@....com>
To: Peter Newman <peternewman@...gle.com>
Cc: corbet@....net, fenghua.yu@...el.com, reinette.chatre@...el.com,
tglx@...utronix.de, mingo@...hat.com, bp@...en8.de,
dave.hansen@...ux.intel.com, x86@...nel.org, hpa@...or.com,
paulmck@...nel.org, rdunlap@...radead.org, tj@...nel.org,
peterz@...radead.org, yanjiewtw@...il.com, kim.phillips@....com,
lukas.bulwahn@...il.com, seanjc@...gle.com, jmattson@...gle.com,
leitao@...ian.org, jpoimboe@...nel.org, rick.p.edgecombe@...el.com,
kirill.shutemov@...ux.intel.com, jithu.joseph@...el.com,
kai.huang@...el.com, kan.liang@...ux.intel.com,
daniel.sneddon@...ux.intel.com, pbonzini@...hat.com, sandipan.das@....com,
ilpo.jarvinen@...ux.intel.com, maciej.wieczor-retman@...el.com,
linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org, eranian@...gle.com,
james.morse@....com
Subject: Re: [RFC PATCH v3 07/17] x86/resctrl: Add support to enable/disable
ABMC feature
Hi Peter,
While working on v4, found few things. Just wanted you to know (mostly FYI.).
On 4/3/24 19:30, Peter Newman wrote:
> Hi Babu,
>
> On Thu, Mar 28, 2024 at 6:07 PM Babu Moger <babu.moger@....com> wrote:
>> struct rdt_fs_context {
>> struct kernfs_fs_context kfc;
>> bool enable_cdpl2;
>> @@ -433,6 +436,7 @@ 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.
>> @@ -448,6 +452,7 @@ struct rdt_hw_resource {
>> unsigned int mbm_width;
>> unsigned int mbm_cfg_mask;
>> bool cdp_enabled;
>> + bool abmc_enabled;
>> };
>>
>> static inline struct rdt_hw_resource *resctrl_to_arch_res(struct rdt_resource *r)
>> @@ -491,6 +496,13 @@ static inline bool resctrl_arch_get_cdp_enabled(enum resctrl_res_level l)
>>
>> int resctrl_arch_set_cdp_enabled(enum resctrl_res_level l, bool enable);
>>
>> +static inline bool resctrl_arch_get_abmc_enabled(enum resctrl_res_level l)
>> +{
>> + return rdt_resources_all[l].abmc_enabled;
>> +}
>
> This inline definition will not work in either this file or
> fs/resctrl/internal.h, following James's change[1] moving the code.
>
> resctrl_arch-definitions are either declared in linux/resctrl.h or
> defined inline in a file like asm/resctrl.h.
Yes, These definitions need to moved to asm/resctrl.h.
Moving that will involve moving few data structure as well.
It is better it is done during fs and arch restructure.
>
>
>> +
>> +int resctrl_arch_set_abmc_enabled(enum resctrl_res_level l, bool enable);
>> +
>> /*
>> * To return the common struct rdt_resource, which is contained in struct
>> * rdt_hw_resource, walk the resctrl member of struct rdt_hw_resource.
>> diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
>> index 05f551bc316e..f49073c86884 100644
>> --- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
>> +++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
>> @@ -850,9 +850,15 @@ static int rdtgroup_mbm_assign_show(struct kernfs_open_file *of,
>> struct seq_file *s, void *v)
>> {
>> struct rdt_resource *r = of->kn->parent->priv;
>> + struct rdt_hw_resource *hw_res = resctrl_to_arch_res(r);
>>
>> - if (r->mbm_assign_capable)
>> + if (r->mbm_assign_capable && hw_res->abmc_enabled) {
>> + seq_puts(s, "[abmc]\n");
>> + seq_puts(s, "legacy_mbm\n");
>> + } else if (r->mbm_assign_capable) {
>> seq_puts(s, "abmc\n");
>> + seq_puts(s, "[legacy_mbm]\n");
>> + }
>
> This looks like it would move to fs/resctrl/rdtgroup.c where it's not
> possible to dereference an rdt_hw_resource struct.
There are two rdtgroup.c files.
0 arch/x86/kernel/cpu/resctrl/rdtgroup.c
1 fs/resctrl/rdtgroup.c
I think this should move to arch rdtgroup.c. It is better it is done
during fs and arch restructure.
>
> It might be helpful to try building your changes on top of James's
> change[1] to get an idea of how this would fit in post-refactoring.
> I'll stop pointing out inconsistencies with his portability scheme
> now.
>
>>
>> return 0;
>> }
>> @@ -2433,6 +2439,74 @@ int resctrl_arch_set_cdp_enabled(enum resctrl_res_level l, bool enable)
>> return 0;
>> }
>>
>> +static void resctrl_abmc_msrwrite(void *arg)
>> +{
>> + bool *enable = arg;
>> + u64 msrval;
>> +
>> + rdmsrl(MSR_IA32_L3_QOS_EXT_CFG, msrval);
>> +
>> + if (*enable)
>> + msrval |= ABMC_ENABLE;
>> + else
>> + msrval &= ~ABMC_ENABLE;
>> +
>> + wrmsrl(MSR_IA32_L3_QOS_EXT_CFG, msrval);
>> +}
>> +
>> +static int resctrl_abmc_setup(enum resctrl_res_level l, bool enable)
>> +{
>> + struct rdt_resource *r = &rdt_resources_all[l].r_resctrl;
>> + struct rdt_domain *d;
>> +
>> + /* Update QOS_CFG MSR on all the CPUs in cpu_mask */
>> + list_for_each_entry(d, &r->domains, list) {
>> + on_each_cpu_mask(&d->cpu_mask, resctrl_abmc_msrwrite, &enable, 1);
>> + resctrl_arch_reset_rmid_all(r, d);
>> + }
>> +
>> + return 0;
>> +}
>> +
>> +static int resctrl_abmc_enable(enum resctrl_res_level l)
>> +{
>> + struct rdt_hw_resource *hw_res = &rdt_resources_all[l];
>> + int ret = 0;
>> +
>> + if (!hw_res->abmc_enabled) {
>> + ret = resctrl_abmc_setup(l, true);
>> + if (!ret)
>> + hw_res->abmc_enabled = true;
>
> Presumably this would be called holding the rdtgroup_mutex? Perhaps a
> lockdep assertion somewhere would be appropriate?
Yes. I have taken care of this.
>
> Thanks!
> -Peter
>
> [1] https://lore.kernel.org/lkml/20240321165106.31602-32-james.morse@arm.com/
>
--
Thanks
Babu Moger
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