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Date: Fri, 15 Oct 2021 15:29:44 -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 17/23] x86/resctrl: Abstract __rmid_read()
Hi James,
On 10/1/2021 9:02 AM, James Morse wrote:
> __rmid_read() selects the specified eventid and returns the counter
> value from the msr. The error handling is architecture specific, and
msr -> MSR
> handled by the callers, rdtgroup_mondata_show() and __mon_event_count().
>
> Error handling should be handled by architecture specific code, as
> a different architecture may have different requirements. MPAM's
> counters can report that they are 'not ready', requiring a second
> read after a short delay. This should be hidden from resctrl.
>
> Make __rmid_read() the architecture specific function for reading
> a counter. Rename it resctrl_arch_rmid_read() and move the error
> handling into it.
>
> Signed-off-by: James Morse <james.morse@....com>
> ---
> Changes since v1:
> * Return EINVAL from the impossible case in __mon_event_count() instead
> of an x86 hardware specific value.
> ---
> arch/x86/kernel/cpu/resctrl/ctrlmondata.c | 4 +--
> arch/x86/kernel/cpu/resctrl/internal.h | 2 +-
> arch/x86/kernel/cpu/resctrl/monitor.c | 42 +++++++++++++++--------
> include/linux/resctrl.h | 1 +
> 4 files changed, 31 insertions(+), 18 deletions(-)
>
> diff --git a/arch/x86/kernel/cpu/resctrl/ctrlmondata.c b/arch/x86/kernel/cpu/resctrl/ctrlmondata.c
> index 25baacd331e0..c8ca7184c6d9 100644
> --- a/arch/x86/kernel/cpu/resctrl/ctrlmondata.c
> +++ b/arch/x86/kernel/cpu/resctrl/ctrlmondata.c
> @@ -579,9 +579,9 @@ int rdtgroup_mondata_show(struct seq_file *m, void *arg)
>
> mon_event_read(&rr, r, d, rdtgrp, evtid, false);
>
> - if (rr.val & RMID_VAL_ERROR)
> + if (rr.err == -EIO)
> seq_puts(m, "Error\n");
> - else if (rr.val & RMID_VAL_UNAVAIL)
> + else if (rr.err == -EINVAL)
> seq_puts(m, "Unavailable\n");
> else
> seq_printf(m, "%llu\n", rr.val * hw_res->mon_scale);
> diff --git a/arch/x86/kernel/cpu/resctrl/internal.h b/arch/x86/kernel/cpu/resctrl/internal.h
> index f3f31315a907..eca7793d3342 100644
> --- a/arch/x86/kernel/cpu/resctrl/internal.h
> +++ b/arch/x86/kernel/cpu/resctrl/internal.h
> @@ -40,7 +40,6 @@
> */
> #define MBM_CNTR_WIDTH_OFFSET_MAX (62 - MBM_CNTR_WIDTH_BASE)
>
> -
> struct rdt_fs_context {
> struct kernfs_fs_context kfc;
> bool enable_cdpl2;
Stray snippet here.
> @@ -94,6 +93,7 @@ struct rmid_read {
> struct rdt_domain *d;
> enum resctrl_event_id evtid;
> bool first;
> + int err;
> u64 val;
> };
>
> diff --git a/arch/x86/kernel/cpu/resctrl/monitor.c b/arch/x86/kernel/cpu/resctrl/monitor.c
> index 35eef49954b0..cf35eaf01042 100644
> --- a/arch/x86/kernel/cpu/resctrl/monitor.c
> +++ b/arch/x86/kernel/cpu/resctrl/monitor.c
> @@ -167,9 +167,9 @@ void resctrl_arch_reset_rmid(struct rdt_resource *r, struct rdt_domain *d,
> memset(am, 0, sizeof(*am));
> }
>
> -static u64 __rmid_read(u32 rmid, enum resctrl_event_id eventid)
> +int resctrl_arch_rmid_read(u32 rmid, enum resctrl_event_id eventid, u64 *val)
> {
> - u64 val;
> + u64 msr_val;
>
> /*
> * As per the SDM, when IA32_QM_EVTSEL.EvtID (bits 7:0) is configured
> @@ -180,14 +180,24 @@ static u64 __rmid_read(u32 rmid, enum resctrl_event_id eventid)
> * are error bits.
> */
> wrmsr(MSR_IA32_QM_EVTSEL, eventid, rmid);
> - rdmsrl(MSR_IA32_QM_CTR, val);
> + rdmsrl(MSR_IA32_QM_CTR, msr_val);
>
> - return val;
> + if (msr_val & RMID_VAL_ERROR)
> + return -EIO;
> + if (msr_val & RMID_VAL_UNAVAIL)
> + return -EINVAL;
> +
> + *val = msr_val;
> +
> + return 0;
> }
>
> static bool rmid_dirty(struct rmid_entry *entry)
> {
> - u64 val = __rmid_read(entry->rmid, QOS_L3_OCCUP_EVENT_ID);
> + u64 val = 0;
> +
> + if (resctrl_arch_rmid_read(entry->rmid, QOS_L3_OCCUP_EVENT_ID, &val))
> + return true;
>
> return val >= resctrl_cqm_threshold;
> }
> @@ -259,8 +269,8 @@ static void add_rmid_to_limbo(struct rmid_entry *entry)
> {
> struct rdt_resource *r;
> struct rdt_domain *d;
> - int cpu;
> - u64 val;
> + int cpu, err;
> + u64 val = 0;
>
> r = &rdt_resources_all[RDT_RESOURCE_L3].r_resctrl;
>
> @@ -268,8 +278,10 @@ static void add_rmid_to_limbo(struct rmid_entry *entry)
> cpu = get_cpu();
> list_for_each_entry(d, &r->domains, list) {
> if (cpumask_test_cpu(cpu, &d->cpu_mask)) {
> - val = __rmid_read(entry->rmid, QOS_L3_OCCUP_EVENT_ID);
> - if (val <= resctrl_cqm_threshold)
> + err = resctrl_arch_rmid_read(entry->rmid,
> + QOS_L3_OCCUP_EVENT_ID,
> + &val);
> + if (err || val <= resctrl_cqm_threshold)
> continue;
> }
>
> @@ -319,15 +331,15 @@ static u64 __mon_event_count(u32 rmid, struct rmid_read *rr)
> {
> struct rdt_hw_resource *hw_res = resctrl_to_arch_res(rr->r);
> struct mbm_state *m;
> - u64 chunks, tval;
> + u64 chunks, tval = 0;
>
> if (rr->first)
> resctrl_arch_reset_rmid(rr->r, rr->d, rmid, rr->evtid);
>
> - tval = __rmid_read(rmid, rr->evtid);
> - if (tval & (RMID_VAL_ERROR | RMID_VAL_UNAVAIL)) {
> - return tval;
> - }
> + rr->err = resctrl_arch_rmid_read(rmid, rr->evtid, &tval);
> + if (rr->err)
> + return rr->err;
> +
> switch (rr->evtid) {
> case QOS_L3_OCCUP_EVENT_ID:
> rr->val += tval;
> @@ -343,7 +355,7 @@ static u64 __mon_event_count(u32 rmid, struct rmid_read *rr)
> * Code would never reach here because an invalid
> * event id would fail the __rmid_read.
> */
> - return RMID_VAL_ERROR;
> + return -EINVAL;
> }
>
mon_event_count() takes action based on return value of
__mon_event_count() that I do not think has been taken into account in
this patch.
> if (rr->first) {
> diff --git a/include/linux/resctrl.h b/include/linux/resctrl.h
> index 04f30d80fc67..01bdd8be590b 100644
> --- a/include/linux/resctrl.h
> +++ b/include/linux/resctrl.h
> @@ -218,6 +218,7 @@ u32 resctrl_arch_get_config(struct rdt_resource *r, struct rdt_domain *d,
> u32 closid, enum resctrl_conf_type type);
> int resctrl_online_domain(struct rdt_resource *r, struct rdt_domain *d);
> void resctrl_offline_domain(struct rdt_resource *r, struct rdt_domain *d);
> +int resctrl_arch_rmid_read(u32 rmid, enum resctrl_event_id eventid, u64 *res);
>
> /**
> * resctrl_arch_reset_rmid() - Reset any private state associated with rmid
>
Reinette
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