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Message-ID: <876af164-c326-4b26-ab56-790f9a36902e@amd.com>
Date: Thu, 9 Nov 2023 14:47:37 -0600
From: "Moger, Babu" <babu.moger@....com>
To: James Morse <james.morse@....com>, x86@...nel.org,
linux-kernel@...r.kernel.org
Cc: Fenghua Yu <fenghua.yu@...el.com>,
Reinette Chatre <reinette.chatre@...el.com>,
Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
H Peter Anvin <hpa@...or.com>,
shameerali.kolothum.thodi@...wei.com,
D Scott Phillips OS <scott@...amperecomputing.com>,
carl@...amperecomputing.com, lcherian@...vell.com,
bobo.shaobowang@...wei.com, tan.shaopeng@...itsu.com,
baolin.wang@...ux.alibaba.com, Jamie Iles <quic_jiles@...cinc.com>,
Xin Hao <xhao@...ux.alibaba.com>, peternewman@...gle.com,
dfustini@...libre.com, amitsinght@...vell.com
Subject: Re: [PATCH v7 15/24] x86/resctrl: Allow arch to allocate memory
needed in resctrl_arch_rmid_read()
Hi James,
On 10/25/23 13:03, James Morse wrote:
> Depending on the number of monitors available, Arm's MPAM may need to
> allocate a monitor prior to reading the counter value. Allocating a
> contended resource may involve sleeping.
>
> add_rmid_to_limbo() calls resctrl_arch_rmid_read() for multiple domains,
> the allocation should be valid for all domains.
This above sentence does not look correct after your previous patch [patch
14]. You removed resctrl_arch_rmid_read() from add_rmid_to_limbo().
Otherwise looks good.
>
> __check_limbo() and mon_event_count() each make multiple calls to
> resctrl_arch_rmid_read(), to avoid extra work on contended systems,
> the allocation should be valid for multiple invocations of
> resctrl_arch_rmid_read().
>
> Add arch hooks for this allocation, which need calling before
> resctrl_arch_rmid_read(). The allocated monitor is passed to
> resctrl_arch_rmid_read(), then freed again afterwards. The helper
> can be called on any CPU, and can sleep.
>
> Tested-by: Shaopeng Tan <tan.shaopeng@...itsu.com>
> Tested-by: Peter Newman <peternewman@...gle.com>
> Reviewed-by: Shaopeng Tan <tan.shaopeng@...itsu.com>
> Reviewed-by: Reinette Chatre <reinette.chatre@...el.com>
> Signed-off-by: James Morse <james.morse@....com>
Reviewed-by: Babu Moger <babu.moger@....com>
> ---
> Changes since v3:
> * Expanded comment.
> * Removed stray header include.
> * Reworded commit message.
> * Made ctx a void * instead of an int.
>
> Changes since v4:
> * Used IS_ERR() in more places.
>
> Changes since v5:
> * Pass the error back from mon_event_read() as -EINVAL/Unavailable.
> * Add some ratelimited warnings when failing to allocate a mon context
>
> Changes since v6:
> * Added a newline.
> ---
> arch/x86/include/asm/resctrl.h | 11 +++++++
> arch/x86/kernel/cpu/resctrl/ctrlmondata.c | 7 +++++
> arch/x86/kernel/cpu/resctrl/internal.h | 1 +
> arch/x86/kernel/cpu/resctrl/monitor.c | 35 +++++++++++++++++++++--
> include/linux/resctrl.h | 5 +++-
> 5 files changed, 55 insertions(+), 4 deletions(-)
>
> diff --git a/arch/x86/include/asm/resctrl.h b/arch/x86/include/asm/resctrl.h
> index 1d274dbabc44..29c4cc343787 100644
> --- a/arch/x86/include/asm/resctrl.h
> +++ b/arch/x86/include/asm/resctrl.h
> @@ -136,6 +136,17 @@ static inline u32 resctrl_arch_rmid_idx_encode(u32 ignored, u32 rmid)
> return rmid;
> }
>
> +/* x86 can always read an rmid, nothing needs allocating */
> +struct rdt_resource;
> +static inline void *resctrl_arch_mon_ctx_alloc(struct rdt_resource *r, int evtid)
> +{
> + might_sleep();
> + return NULL;
> +};
> +
> +static inline void resctrl_arch_mon_ctx_free(struct rdt_resource *r, int evtid,
> + void *ctx) { };
> +
> void resctrl_cpu_detect(struct cpuinfo_x86 *c);
>
> #else
> diff --git a/arch/x86/kernel/cpu/resctrl/ctrlmondata.c b/arch/x86/kernel/cpu/resctrl/ctrlmondata.c
> index d07f99245851..a033e8e32108 100644
> --- a/arch/x86/kernel/cpu/resctrl/ctrlmondata.c
> +++ b/arch/x86/kernel/cpu/resctrl/ctrlmondata.c
> @@ -546,6 +546,11 @@ void mon_event_read(struct rmid_read *rr, struct rdt_resource *r,
> rr->d = d;
> rr->val = 0;
> rr->first = first;
> + rr->arch_mon_ctx = resctrl_arch_mon_ctx_alloc(r, evtid);
> + if (IS_ERR(rr->arch_mon_ctx)) {
> + rr->err = -EINVAL;
> + return;
> + }
>
> cpu = cpumask_any_housekeeping(&d->cpu_mask);
>
> @@ -559,6 +564,8 @@ void mon_event_read(struct rmid_read *rr, struct rdt_resource *r,
> smp_call_function_any(&d->cpu_mask, mon_event_count, rr, 1);
> else
> smp_call_on_cpu(cpu, smp_mon_event_count, rr, false);
> +
> + resctrl_arch_mon_ctx_free(r, evtid, rr->arch_mon_ctx);
> }
>
> int rdtgroup_mondata_show(struct seq_file *m, void *arg)
> diff --git a/arch/x86/kernel/cpu/resctrl/internal.h b/arch/x86/kernel/cpu/resctrl/internal.h
> index 33e24fcc8dd0..bb07b9b01e36 100644
> --- a/arch/x86/kernel/cpu/resctrl/internal.h
> +++ b/arch/x86/kernel/cpu/resctrl/internal.h
> @@ -138,6 +138,7 @@ struct rmid_read {
> bool first;
> int err;
> u64 val;
> + void *arch_mon_ctx;
> };
>
> extern bool rdt_alloc_capable;
> diff --git a/arch/x86/kernel/cpu/resctrl/monitor.c b/arch/x86/kernel/cpu/resctrl/monitor.c
> index 409817b0ae2c..1ca8db8c82cc 100644
> --- a/arch/x86/kernel/cpu/resctrl/monitor.c
> +++ b/arch/x86/kernel/cpu/resctrl/monitor.c
> @@ -269,7 +269,7 @@ static u64 mbm_overflow_count(u64 prev_msr, u64 cur_msr, unsigned int width)
>
> int resctrl_arch_rmid_read(struct rdt_resource *r, struct rdt_domain *d,
> u32 unused, u32 rmid, enum resctrl_event_id eventid,
> - u64 *val)
> + u64 *val, void *ignored)
> {
> struct rdt_hw_resource *hw_res = resctrl_to_arch_res(r);
> struct rdt_hw_domain *hw_dom = resctrl_to_arch_dom(d);
> @@ -324,9 +324,17 @@ void __check_limbo(struct rdt_domain *d, bool force_free)
> u32 idx_limit = resctrl_arch_system_num_rmid_idx();
> struct rmid_entry *entry;
> u32 idx, cur_idx = 1;
> + void *arch_mon_ctx;
> bool rmid_dirty;
> u64 val = 0;
>
> + arch_mon_ctx = resctrl_arch_mon_ctx_alloc(r, QOS_L3_OCCUP_EVENT_ID);
> + if (IS_ERR(arch_mon_ctx)) {
> + pr_warn_ratelimited("Failed to allocate monitor context: %ld",
> + PTR_ERR(arch_mon_ctx));
> + return;
> + }
> +
> /*
> * Skip RMID 0 and start from RMID 1 and check all the RMIDs that
> * are marked as busy for occupancy < threshold. If the occupancy
> @@ -340,7 +348,8 @@ void __check_limbo(struct rdt_domain *d, bool force_free)
>
> entry = __rmid_entry(idx);
> if (resctrl_arch_rmid_read(r, d, entry->closid, entry->rmid,
> - QOS_L3_OCCUP_EVENT_ID, &val)) {
> + QOS_L3_OCCUP_EVENT_ID, &val,
> + arch_mon_ctx)) {
> rmid_dirty = true;
> } else {
> rmid_dirty = (val >= resctrl_rmid_realloc_threshold);
> @@ -353,6 +362,8 @@ void __check_limbo(struct rdt_domain *d, bool force_free)
> }
> cur_idx = idx + 1;
> }
> +
> + resctrl_arch_mon_ctx_free(r, QOS_L3_OCCUP_EVENT_ID, arch_mon_ctx);
> }
>
> bool has_busy_rmid(struct rdt_domain *d)
> @@ -533,7 +544,7 @@ static int __mon_event_count(u32 closid, u32 rmid, struct rmid_read *rr)
> }
>
> rr->err = resctrl_arch_rmid_read(rr->r, rr->d, closid, rmid, rr->evtid,
> - &tval);
> + &tval, rr->arch_mon_ctx);
> if (rr->err)
> return rr->err;
>
> @@ -744,11 +755,27 @@ static void mbm_update(struct rdt_resource *r, struct rdt_domain *d,
> if (is_mbm_total_enabled()) {
> rr.evtid = QOS_L3_MBM_TOTAL_EVENT_ID;
> rr.val = 0;
> + rr.arch_mon_ctx = resctrl_arch_mon_ctx_alloc(rr.r, rr.evtid);
> + if (IS_ERR(rr.arch_mon_ctx)) {
> + pr_warn_ratelimited("Failed to allocate monitor context: %ld",
> + PTR_ERR(rr.arch_mon_ctx));
> + return;
> + }
> +
> __mon_event_count(closid, rmid, &rr);
> +
> + resctrl_arch_mon_ctx_free(rr.r, rr.evtid, rr.arch_mon_ctx);
> }
> if (is_mbm_local_enabled()) {
> rr.evtid = QOS_L3_MBM_LOCAL_EVENT_ID;
> rr.val = 0;
> + rr.arch_mon_ctx = resctrl_arch_mon_ctx_alloc(rr.r, rr.evtid);
> + if (IS_ERR(rr.arch_mon_ctx)) {
> + pr_warn_ratelimited("Failed to allocate monitor context: %ld",
> + PTR_ERR(rr.arch_mon_ctx));
> + return;
> + }
> +
> __mon_event_count(closid, rmid, &rr);
>
> /*
> @@ -758,6 +785,8 @@ static void mbm_update(struct rdt_resource *r, struct rdt_domain *d,
> */
> if (is_mba_sc(NULL))
> mbm_bw_count(closid, rmid, &rr);
> +
> + resctrl_arch_mon_ctx_free(rr.r, rr.evtid, rr.arch_mon_ctx);
> }
> }
>
> diff --git a/include/linux/resctrl.h b/include/linux/resctrl.h
> index 8649fc84aac2..bf460c912bf5 100644
> --- a/include/linux/resctrl.h
> +++ b/include/linux/resctrl.h
> @@ -235,6 +235,9 @@ void resctrl_offline_domain(struct rdt_resource *r, struct rdt_domain *d);
> * @rmid: rmid of the counter to read.
> * @eventid: eventid to read, e.g. L3 occupancy.
> * @val: result of the counter read in bytes.
> + * @arch_mon_ctx: An architecture specific value from
> + * resctrl_arch_mon_ctx_alloc(), for MPAM this identifies
> + * the hardware monitor allocated for this read request.
> *
> * Some architectures need to sleep when first programming some of the counters.
> * (specifically: arm64's MPAM cache occupancy counters can return 'not ready'
> @@ -248,7 +251,7 @@ void resctrl_offline_domain(struct rdt_resource *r, struct rdt_domain *d);
> */
> int resctrl_arch_rmid_read(struct rdt_resource *r, struct rdt_domain *d,
> u32 closid, u32 rmid, enum resctrl_event_id eventid,
> - u64 *val);
> + u64 *val, void *arch_mon_ctx);
>
> /**
> * resctrl_arch_rmid_read_context_check() - warn about invalid contexts
--
Thanks
Babu Moger
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