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Message-ID: <f67e36b2-709f-485f-a0db-388247ff6b37@intel.com>
Date: Thu, 1 Aug 2024 11:16:33 -0700
From: Reinette Chatre <reinette.chatre@...el.com>
To: Peter Newman <peternewman@...gle.com>, Fenghua Yu <fenghua.yu@...el.com>
CC: Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>,
Borislav Petkov <bp@...en8.de>, Dave Hansen <dave.hansen@...ux.intel.com>,
<x86@...nel.org>, "H . Peter Anvin" <hpa@...or.com>, Shaopeng Tan
<tan.shaopeng@...itsu.com>, James Morse <james.morse@....com>, Babu Moger
<babu.moger@....com>, Tony Luck <tony.luck@...el.com>, Maciej Wieczor-Retman
<maciej.wieczor-retman@...el.com>, <linux-kernel@...r.kernel.org>,
<eranian@...gle.com>, <irogers@...gle.com>, <namhyung@...gle.com>
Subject: Re: [PATCH] x86/resctrl: Fix arch_mbm_* array overrun on SNC
Hi Peter,
On 7/22/24 1:46 PM, Peter Newman wrote:
> When using resctrl on systems with Sub-NUMA Clustering enabled,
> monitoring groups may be allocated RMID values which would overrun the
> arch_mbm_{local,total} arrays.
>
> This is due to inconsistencies in whether the SNC-adjusted num_rmid
> value or the unadjusted value in resctrl_arch_system_num_rmid_idx() is
> used. The num_rmid value for the L3 resource is currently:
>
> resctrl_arch_system_num_rmid_idx() / snc_nodes_per_l3_cache
>
> As a simple fix, make resctrl_arch_system_num_rmid_idx() return the
> SNC-adjusted, L3 num_rmid value on x86.
>
Thank you very much for finding, root-causing, and providing a fix for
the issue.
> Fixes: e13db55b5a0d ("x86/resctrl: Introduce snc_nodes_per_l3_cache")
> Signed-off-by: Peter Newman <peternewman@...gle.com>
> ---
> arch/x86/include/asm/resctrl.h | 6 ------
> arch/x86/kernel/cpu/resctrl/core.c | 8 ++++++++
> include/linux/resctrl.h | 3 +++
> 3 files changed, 11 insertions(+), 6 deletions(-)
>
> diff --git a/arch/x86/include/asm/resctrl.h b/arch/x86/include/asm/resctrl.h
> index 12dbd2588ca7..8b1b6ce1e51b 100644
> --- a/arch/x86/include/asm/resctrl.h
> +++ b/arch/x86/include/asm/resctrl.h
> @@ -156,12 +156,6 @@ static inline void resctrl_sched_in(struct task_struct *tsk)
> __resctrl_sched_in(tsk);
> }
>
> -static inline u32 resctrl_arch_system_num_rmid_idx(void)
> -{
> - /* RMID are independent numbers for x86. num_rmid_idx == num_rmid */
> - return boot_cpu_data.x86_cache_max_rmid + 1;
> -}
> -
> static inline void resctrl_arch_rmid_idx_decode(u32 idx, u32 *closid, u32 *rmid)
> {
> *rmid = idx;
> diff --git a/arch/x86/kernel/cpu/resctrl/core.c b/arch/x86/kernel/cpu/resctrl/core.c
> index 1930fce9dfe9..8591d53c144b 100644
> --- a/arch/x86/kernel/cpu/resctrl/core.c
> +++ b/arch/x86/kernel/cpu/resctrl/core.c
> @@ -119,6 +119,14 @@ struct rdt_hw_resource rdt_resources_all[] = {
> },
> };
>
> +u32 resctrl_arch_system_num_rmid_idx(void)
> +{
> + struct rdt_resource *r = &rdt_resources_all[RDT_RESOURCE_L3].r_resctrl;
> +
> + /* RMID are independent numbers for x86. num_rmid_idx == num_rmid */
> + return r->num_rmid;
> +}
> +
> /*
> * cache_alloc_hsw_probe() - Have to probe for Intel haswell server CPUs
> * as they do not have CPUID enumeration support for Cache allocation.
> diff --git a/include/linux/resctrl.h b/include/linux/resctrl.h
> index b0875b99e811..43ac241471b3 100644
> --- a/include/linux/resctrl.h
> +++ b/include/linux/resctrl.h
> @@ -248,6 +248,9 @@ struct resctrl_schema {
>
> /* The number of closid supported by this resource regardless of CDP */
> u32 resctrl_arch_get_num_closid(struct rdt_resource *r);
> +
> +u32 resctrl_arch_system_num_rmid_idx(void);
> +
nit: the additional empty lines are unnecessary.
> int resctrl_arch_update_domains(struct rdt_resource *r, u32 closid);
>
> /*
| Reviewed-by: Reinette Chatre <reinette.chatre@...el.com>
Reinette
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