Re: [PATCH v1 07/20] x86/resctrl: Remove architecture copy of mbps_val

[Reinette Chatre]

Hi James,

On 7/29/2021 3:35 PM, James Morse wrote:
> The resctrl arch code provides a second configuration array mbps_val[]
> for the mba socftware controller.

"mba socftware" -> "MBA software"

> Since resctrl switched over to allocating and freeing its own array
> when needed, nothing uses the arch code version.
>
> Remove it.
>
> Signed-off-by: James Morse <james.morse@xxxxxxx>
> ---
>   arch/x86/kernel/cpu/resctrl/core.c     | 20 ++++----------------
>   arch/x86/kernel/cpu/resctrl/internal.h |  4 +---
>   arch/x86/kernel/cpu/resctrl/rdtgroup.c |  2 +-
>   3 files changed, 6 insertions(+), 20 deletions(-)
>
> diff --git a/arch/x86/kernel/cpu/resctrl/core.c b/arch/x86/kernel/cpu/resctrl/core.c
> index 56b3541617b5..e864dbc6fe3d 100644
> --- a/arch/x86/kernel/cpu/resctrl/core.c
> +++ b/arch/x86/kernel/cpu/resctrl/core.c
> @@ -397,7 +397,7 @@ struct rdt_domain *rdt_find_domain(struct rdt_resource *r, int id,
>   	return NULL;
>   }
>   
> -void setup_default_ctrlval(struct rdt_resource *r, u32 *dc, u32 *dm)
> +void setup_default_ctrlval(struct rdt_resource *r, u32 *dc)
>   {
>   	struct rdt_hw_resource *hw_res = resctrl_to_arch_res(r);
>   	int i;
> @@ -406,12 +406,9 @@ void setup_default_ctrlval(struct rdt_resource *r, u32 *dc, u32 *dm)
>   	 * Initialize the Control MSRs to having no control.
>   	 * For Cache Allocation: Set all bits in cbm
>   	 * For Memory Allocation: Set b/w requested to 100%
> -	 * and the bandwidth in MBps to U32_MAX
>   	 */
> -	for (i = 0; i < hw_res->num_closid; i++, dc++, dm++) {
> +	for (i = 0; i < hw_res->num_closid; i++, dc++)
>   		*dc = r->default_ctrl;
> -		*dm = MBA_MAX_MBPS;
> -	}

Since this function used to reset the array to default I was expecting 
its callers to now reset the new array (more below).

>   }
>   
>   static int domain_setup_ctrlval(struct rdt_resource *r, struct rdt_domain *d)
> @@ -419,23 +416,15 @@ static int domain_setup_ctrlval(struct rdt_resource *r, struct rdt_domain *d)
>   	struct rdt_hw_resource *hw_res = resctrl_to_arch_res(r);
>   	struct rdt_hw_domain *hw_dom = resctrl_to_arch_dom(d);
>   	struct msr_param m;
> -	u32 *dc, *dm;
> +	u32 *dc;
>   
>   	dc = kmalloc_array(hw_res->num_closid, sizeof(*hw_dom->ctrl_val),
>   			   GFP_KERNEL);
>   	if (!dc)
>   		return -ENOMEM;
>   
> -	dm = kmalloc_array(hw_res->num_closid, sizeof(*hw_dom->mbps_val),
> -			   GFP_KERNEL);
> -	if (!dm) {
> -		kfree(dc);
> -		return -ENOMEM;
> -	}
> -
>   	hw_dom->ctrl_val = dc;
> -	hw_dom->mbps_val = dm;
> -	setup_default_ctrlval(r, dc, dm);
> +	setup_default_ctrlval(r, dc);
>   
>   	m.low = 0;
>   	m.high = hw_res->num_closid;
> @@ -527,7 +516,6 @@ static void domain_remove_cpu(int cpu, struct rdt_resource *r)
>   			d->plr->d = NULL;
>   
>   		kfree(hw_dom->ctrl_val);
> -		kfree(hw_dom->mbps_val);
>   		kfree(hw_dom);
>   		return;
>   	}
> diff --git a/arch/x86/kernel/cpu/resctrl/internal.h b/arch/x86/kernel/cpu/resctrl/internal.h
> index a7e2cbce29d5..796e13a0e8dc 100644
> --- a/arch/x86/kernel/cpu/resctrl/internal.h
> +++ b/arch/x86/kernel/cpu/resctrl/internal.h
> @@ -308,14 +308,12 @@ struct mbm_state {
>    *			  a resource
>    * @d_resctrl:	Properties exposed to the resctrl file system
>    * @ctrl_val:	array of cache or mem ctrl values (indexed by CLOSID)
> - * @mbps_val:	When mba_sc is enabled, this holds the bandwidth in MBps
>    *
>    * Members of this structure are accessed via helpers that provide abstraction.
>    */
>   struct rdt_hw_domain {
>   	struct rdt_domain		d_resctrl;
>   	u32				*ctrl_val;
> -	u32				*mbps_val;
>   };
>   
>   static inline struct rdt_hw_domain *resctrl_to_arch_dom(struct rdt_domain *r)
> @@ -529,7 +527,7 @@ void mbm_setup_overflow_handler(struct rdt_domain *dom,
>   void mbm_handle_overflow(struct work_struct *work);
>   void __init intel_rdt_mbm_apply_quirk(void);
>   bool is_mba_sc(struct rdt_resource *r);
> -void setup_default_ctrlval(struct rdt_resource *r, u32 *dc, u32 *dm);
> +void setup_default_ctrlval(struct rdt_resource *r, u32 *dc);
>   u32 delay_bw_map(unsigned long bw, struct rdt_resource *r);
>   void cqm_setup_limbo_handler(struct rdt_domain *dom, unsigned long delay_ms);
>   void cqm_handle_limbo(struct work_struct *work);
> diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> index 185f9bb992d1..297c20491549 100644
> --- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> +++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> @@ -1906,7 +1906,7 @@ static int set_mba_sc(bool mba_sc)
>   	r->membw.mba_sc = mba_sc;
>   	list_for_each_entry(d, &r->domains, list) {
>   		hw_dom = resctrl_to_arch_dom(d);
> -		setup_default_ctrlval(r, hw_dom->ctrl_val, hw_dom->mbps_val);
> +		setup_default_ctrlval(r, hw_dom->ctrl_val);
>   	}
>   

I am wondering why new array is not reset instead of original at this 
call site? oh ... I see it is removed in following patch BUT it mentions 
that it is ok because reset_all_ctrls() does similar reset ... but it 
does not seem to do so for mbps_val.

Reinette