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Date: Fri, 15 Oct 2021 15:29:20 -0700
From: Reinette Chatre <reinette.chatre@...el.com>
To: James Morse <james.morse@....com>, <x86@...nel.org>,
<linux-kernel@...r.kernel.org>
CC: Fenghua Yu <fenghua.yu@...el.com>,
Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
H Peter Anvin <hpa@...or.com>,
Babu Moger <Babu.Moger@....com>,
<shameerali.kolothum.thodi@...wei.com>,
Jamie Iles <jamie@...iainc.com>,
"D Scott Phillips OS" <scott@...amperecomputing.com>,
<lcherian@...vell.com>, <bobo.shaobowang@...wei.com>,
<tan.shaopeng@...itsu.com>
Subject: Re: [PATCH v2 15/23] x86/recstrl: Add per-rmid arch private storage
for overflow and chunks
Hi James,
On 10/1/2021 9:02 AM, James Morse wrote:
> resctrl_arch_rmid_read() is intended as the function that an
> architecture agnostic resctrl filesystem driver can use to
> read a value in bytes from a counter. Currently the function returns
resctrl_arch_rmid_read() does not exist at this point and is also not
introduced in this patch.
> the mbm values in chunks directly from hardware. For bandwidth
Could you please replace mbm with MBM throughout the series?
> counters the resctrl filesystem uses this to calculate the number of
> bytes ever seen.
>
> MPAM's scaling of counters can be changed at runtime, reducing the
> resolution but increasing the range. When this is changed the prev_msr
> values need to be converted by the architecture code.
>
> Add an array for per-rmid private storage. The prev_msr and chunks
> values will move here to allow resctrl_arch_rmid_read() to always
> return the number of bytes read by this counter without assistance
> from the filesystem. The values are moved in later patches when
> the overflow and correction calls are moved into
> resctrl_arch_rmid_read().
>
> Signed-off-by: James Morse <james.morse@....com>
> ---
> arch/x86/kernel/cpu/resctrl/core.c | 34 ++++++++++++++++++++++++++
> arch/x86/kernel/cpu/resctrl/internal.h | 13 ++++++++++
> 2 files changed, 47 insertions(+)
>
> diff --git a/arch/x86/kernel/cpu/resctrl/core.c b/arch/x86/kernel/cpu/resctrl/core.c
> index 583fb41db06d..f527489a607a 100644
> --- a/arch/x86/kernel/cpu/resctrl/core.c
> +++ b/arch/x86/kernel/cpu/resctrl/core.c
> @@ -413,6 +413,8 @@ void setup_default_ctrlval(struct rdt_resource *r, u32 *dc)
>
> void domain_free(struct rdt_hw_domain *hw_dom)
> {
> + kfree(hw_dom->arch_mbm_total);
> + kfree(hw_dom->arch_mbm_local);
> kfree(hw_dom->ctrl_val);
> kfree(hw_dom);
> }
> @@ -438,6 +440,33 @@ static int domain_setup_ctrlval(struct rdt_resource *r, struct rdt_domain *d)
> return 0;
> }
>
> +/**
> + * arch_domain_mbm_alloc() - Allocate arch private storage for the mbm counters
mbm -> MBM in comments also please .
> + * @num_rmid: The size of the mbm counter array
> + * @hw_dom: The domain that owns the allocated the arrays
the allocated the -> the allocated
> + *
> + * On error, call domain_free()
When following kerneldoc please use "Return:" to indicate the return
section. It will help to run scripts/kernel-doc on these changes to make
sure no new kernel-doc issues are introduced.
> + */
> +static int arch_domain_mbm_alloc(u32 num_rmid, struct rdt_hw_domain *hw_dom)
> +{
> + size_t tsize;
> +
> + if (is_mbm_total_enabled()) {
> + tsize = sizeof(*hw_dom->arch_mbm_total);
> + hw_dom->arch_mbm_total = kcalloc(num_rmid, tsize, GFP_KERNEL);
> + if (!hw_dom->arch_mbm_total)
> + return -ENOMEM;
> + }
> + if (is_mbm_local_enabled()) {
> + tsize = sizeof(*hw_dom->arch_mbm_local);
> + hw_dom->arch_mbm_local = kcalloc(num_rmid, tsize, GFP_KERNEL);
> + if (!hw_dom->arch_mbm_local)
> + return -ENOMEM;
> + }
> +
Proper cleanup on error should be done in this function. Please do not
use domain_free() as cleanup for what can be done in this function. I
see domain_free() as the higher level error control ... like when a
wrapper function calls arch_domain_mbm_alloc() and then something else
fails after that ... then domain_free() would be that higher level error
handling.
> + return 0;
> +}
> +
> /*
> * domain_add_cpu - Add a cpu to a resource's domain list.
> *
> @@ -487,6 +516,11 @@ static void domain_add_cpu(int cpu, struct rdt_resource *r)
> return;
> }
>
> + if (r->mon_capable && arch_domain_mbm_alloc(r->num_rmid, hw_dom)) {
> + domain_free(hw_dom);
> + return;
> + }
> +
> list_add_tail(&d->list, add_pos);
>
> err = resctrl_online_domain(r, d);
> diff --git a/arch/x86/kernel/cpu/resctrl/internal.h b/arch/x86/kernel/cpu/resctrl/internal.h
> index 0a5721e1cc07..aaae900a8ef3 100644
> --- a/arch/x86/kernel/cpu/resctrl/internal.h
> +++ b/arch/x86/kernel/cpu/resctrl/internal.h
> @@ -303,17 +303,30 @@ struct mbm_state {
> bool delta_comp;
> };
>
> +/**
> + * struct arch_mbm_state - values used to compute resctrl_arch_rmid_read()s
> + * return value.
> + * @prev_msr Value of IA32_QM_CTR for this RMID last time we read it
Missing a ":"?
Please do not use "we".
This is a description of a struct ... can the doc elaborate on what
"this RMID" means?
> + */
> +struct arch_mbm_state {
> + u64 prev_msr;
> +};
> +
> /**
> * struct rdt_hw_domain - Arch private attributes of a set of CPUs that share
> * a resource
> * @d_resctrl: Properties exposed to the resctrl file system
> * @ctrl_val: array of cache or mem ctrl values (indexed by CLOSID)
> + * @arch_mbm_total: arch private state for MBM total bandwidth
> + * @arch_mbm_local: arch private state for MBM local bandwidth
> *
> * Members of this structure are accessed via helpers that provide abstraction.
> */
> struct rdt_hw_domain {
> struct rdt_domain d_resctrl;
> u32 *ctrl_val;
> + struct arch_mbm_state *arch_mbm_total;
> + struct arch_mbm_state *arch_mbm_local;
> };
>
> static inline struct rdt_hw_domain *resctrl_to_arch_dom(struct rdt_domain *r)
>
Reinette
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