From nobody Mon Sep 15 08:07:28 2025 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id E78FDC3DA78 for ; Fri, 13 Jan 2023 18:03:04 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229977AbjAMSDD (ORCPT ); Fri, 13 Jan 2023 13:03:03 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43982 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230117AbjAMSBi (ORCPT ); Fri, 13 Jan 2023 13:01:38 -0500 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 4DB20DFD9 for ; Fri, 13 Jan 2023 09:56:07 -0800 (PST) Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id B6C9A1764; Fri, 13 Jan 2023 09:56:49 -0800 (PST) Received: from merodach.members.linode.com (unknown [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 2B7263F67D; Fri, 13 Jan 2023 09:56:05 -0800 (PST) From: James Morse To: x86@kernel.org, linux-kernel@vger.kernel.org Cc: Fenghua Yu , Reinette Chatre , Thomas Gleixner , Ingo Molnar , Borislav Petkov , H Peter Anvin , Babu Moger , James Morse , shameerali.kolothum.thodi@huawei.com, D Scott Phillips OS , carl@os.amperecomputing.com, lcherian@marvell.com, bobo.shaobowang@huawei.com, tan.shaopeng@fujitsu.com, xingxin.hx@openanolis.org, baolin.wang@linux.alibaba.com, Jamie Iles , Xin Hao , peternewman@google.com Subject: [PATCH v2 09/18] x86/resctrl: Allow resctrl_arch_rmid_read() to sleep Date: Fri, 13 Jan 2023 17:54:50 +0000 Message-Id: <20230113175459.14825-10-james.morse@arm.com> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20230113175459.14825-1-james.morse@arm.com> References: <20230113175459.14825-1-james.morse@arm.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" MPAM's cache occupancy counters can take a little while to settle once the monitor has been configured. The maximum settling time is described to the driver via a firmware table. The value could be large enough that it makes sense to sleep. To avoid exposing this to resctrl, it should be hidden behind MPAM's resctrl_arch_rmid_read(). But add_rmid_to_limbo() calls resctrl_arch_rmid_read() from a non-preemptible context. add_rmid_to_limbo() is opportunistically reading the L3 occupancy counter on this domain to avoid adding the RMID to limbo if this domain's value has drifted below resctrl_rmid_realloc_threshold since the limbo handler last ran. Determining 'this domain' involves disabling preeption to prevent the thread being migrated to CPUs in a different domain between the check and resctrl_arch_rmid_read() call. The check is skipped for all remote domains. Instead, call resctrl_arch_rmid_read() for each domain, and get it to read the arch specific counter via IPI if its called on a CPU outside the target domain. By covering remote domains, this change stops the limbo handler from being started unnecessarily. This also allows resctrl_arch_rmid_read() to sleep. Tested-by: Shaopeng Tan Signed-off-by: James Morse --- The alternative is to remove the counter read from this path altogether, and assume user-space would never try to re-allocate the last RMID before the limbo handler runs next. --- arch/x86/kernel/cpu/resctrl/monitor.c | 58 ++++++++++++++++++--------- 1 file changed, 38 insertions(+), 20 deletions(-) diff --git a/arch/x86/kernel/cpu/resctrl/monitor.c b/arch/x86/kernel/cpu/re= sctrl/monitor.c index d309b830aeb2..d6ae4b713801 100644 --- a/arch/x86/kernel/cpu/resctrl/monitor.c +++ b/arch/x86/kernel/cpu/resctrl/monitor.c @@ -206,17 +206,19 @@ static u64 mbm_overflow_count(u64 prev_msr, u64 cur_m= sr, unsigned int width) return chunks >> shift; } =20 -int resctrl_arch_rmid_read(struct rdt_resource *r, struct rdt_domain *d, - u32 closid, u32 rmid, enum resctrl_event_id eventid, - u64 *val) +struct __rmid_read_arg { - struct rdt_hw_resource *hw_res =3D resctrl_to_arch_res(r); - struct rdt_hw_domain *hw_dom =3D resctrl_to_arch_dom(d); - struct arch_mbm_state *am; - u64 msr_val, chunks; + u32 rmid; + enum resctrl_event_id eventid; =20 - if (!cpumask_test_cpu(smp_processor_id(), &d->cpu_mask)) - return -EINVAL; + u64 msr_val; +}; + +static void __rmid_read(void *arg) +{ + enum resctrl_event_id eventid =3D ((struct __rmid_read_arg *)arg)->eventi= d; + u32 rmid =3D ((struct __rmid_read_arg *)arg)->rmid; + u64 msr_val; =20 /* * As per the SDM, when IA32_QM_EVTSEL.EvtID (bits 7:0) is configured @@ -229,6 +231,28 @@ int resctrl_arch_rmid_read(struct rdt_resource *r, str= uct rdt_domain *d, wrmsr(MSR_IA32_QM_EVTSEL, eventid, rmid); rdmsrl(MSR_IA32_QM_CTR, msr_val); =20 + ((struct __rmid_read_arg *)arg)->msr_val =3D msr_val; +} + +int resctrl_arch_rmid_read(struct rdt_resource *r, struct rdt_domain *d, + u32 closid, u32 rmid, enum resctrl_event_id eventid, + u64 *val) +{ + struct rdt_hw_resource *hw_res =3D resctrl_to_arch_res(r); + struct rdt_hw_domain *hw_dom =3D resctrl_to_arch_dom(d); + struct __rmid_read_arg arg; + struct arch_mbm_state *am; + u64 msr_val, chunks; + int err; + + arg.rmid =3D rmid; + arg.eventid =3D eventid; + + err =3D smp_call_function_any(&d->cpu_mask, __rmid_read, &arg, true); + if (err) + return err; + + msr_val =3D arg.msr_val; if (msr_val & RMID_VAL_ERROR) return -EIO; if (msr_val & RMID_VAL_UNAVAIL) @@ -383,23 +407,18 @@ static void add_rmid_to_limbo(struct rmid_entry *entr= y) { struct rdt_resource *r =3D &rdt_resources_all[RDT_RESOURCE_L3].r_resctrl; struct rdt_domain *d; - int cpu, err; u64 val =3D 0; u32 idx; + int err; =20 idx =3D resctrl_arch_rmid_idx_encode(entry->closid, entry->rmid); =20 entry->busy =3D 0; - cpu =3D get_cpu(); list_for_each_entry(d, &r->domains, list) { - if (cpumask_test_cpu(cpu, &d->cpu_mask)) { - err =3D resctrl_arch_rmid_read(r, d, entry->closid, - entry->rmid, - QOS_L3_OCCUP_EVENT_ID, - &val); - if (err || val <=3D resctrl_rmid_realloc_threshold) - continue; - } + err =3D resctrl_arch_rmid_read(r, d, entry->closid, entry->rmid, + QOS_L3_OCCUP_EVENT_ID, &val); + if (err || val <=3D resctrl_rmid_realloc_threshold) + continue; =20 /* * For the first limbo RMID in the domain, @@ -410,7 +429,6 @@ static void add_rmid_to_limbo(struct rmid_entry *entry) set_bit(idx, d->rmid_busy_llc); entry->busy++; } - put_cpu(); =20 if (entry->busy) rmid_limbo_count++; --=20 2.30.2