From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 94CF5266560; Fri, 12 Sep 2025 15:55:22 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1757692524; cv=none; b=oz6rblZWT+n2PKigy7i9INVZukJ2zL2QAD+26sRSTr7aMLYmRYDsaVjdF/oEs5PqEBfLFKwcRUvaJoAciaPA42B2Kjhzd7G6ynusGTBvSv9saHx+YVitLGAjf810PdLxHQ/qhPsCZpdcgvpPlEedDwlzcyUBrtf2/6qwhGtbCYU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1757692524; c=relaxed/simple; bh=5q8RUlkeA6pyHgeVhdpx3JeIpyv4wzgt8AxLFO5mZng=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=lNZTaSGFvWCDsL+/38BAYc3JzPblm4laO4seqo4QQQnbJSOduO2OCCJWWrtLXs1hrPcWb2N/0sqIoQH4rrRJH3KviMF6hHiAawyy14C2IOneDMEsdhsL+N5eI9JdO6Blt90hSpd1W+n8oogYPWEzB9J/1FsikgpFLwWcyfVw9MM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com 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 9F0591515; Fri, 12 Sep 2025 08:55:13 -0700 (PDT) Received: from [10.1.196.46] (e134344.arm.com [10.1.196.46]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 6CEAE3F66E; Fri, 12 Sep 2025 08:55:17 -0700 (PDT) Message-ID: <53eddf53-a610-4420-9021-658fdf31aebe@arm.com> Date: Fri, 12 Sep 2025 16:55:16 +0100 Precedence: bulk X-Mailing-List: linux-acpi@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 24/29] arm_mpam: Track bandwidth counter state for overflow and power management To: James Morse , linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-acpi@vger.kernel.org Cc: D Scott Phillips OS , carl@os.amperecomputing.com, lcherian@marvell.com, bobo.shaobowang@huawei.com, tan.shaopeng@fujitsu.com, baolin.wang@linux.alibaba.com, Jamie Iles , Xin Hao , peternewman@google.com, dfustini@baylibre.com, amitsinght@marvell.com, David Hildenbrand , Dave Martin , Koba Ko , Shanker Donthineni , fenghuay@nvidia.com, baisheng.gao@unisoc.com, Jonathan Cameron , Rob Herring , Rohit Mathew , Rafael Wysocki , Len Brown , Lorenzo Pieralisi , Hanjun Guo , Sudeep Holla , Catalin Marinas , Will Deacon , Greg Kroah-Hartman , Danilo Krummrich References: <20250910204309.20751-1-james.morse@arm.com> <20250910204309.20751-25-james.morse@arm.com> From: Ben Horgan Content-Language: en-US In-Reply-To: <20250910204309.20751-25-james.morse@arm.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Hi James, On 9/10/25 21:43, James Morse wrote: > Bandwidth counters need to run continuously to correctly reflect the > bandwidth. > > The value read may be lower than the previous value read in the case > of overflow and when the hardware is reset due to CPU hotplug. > > Add struct mbwu_state to track the bandwidth counter to allow overflow > and power management to be handled. > > Signed-off-by: James Morse > --- > Changes since v1: > * Fixed lock/unlock typo. > --- > drivers/resctrl/mpam_devices.c | 154 +++++++++++++++++++++++++++++++- > drivers/resctrl/mpam_internal.h | 23 +++++ > 2 files changed, 175 insertions(+), 2 deletions(-) > > diff --git a/drivers/resctrl/mpam_devices.c b/drivers/resctrl/mpam_devices.c > index 1543c33c5d6a..eeb62ed94520 100644 > --- a/drivers/resctrl/mpam_devices.c > +++ b/drivers/resctrl/mpam_devices.c > @@ -918,6 +918,7 @@ static void gen_msmon_ctl_flt_vals(struct mon_read *m, u32 *ctl_val, > *ctl_val |= MSMON_CFG_x_CTL_MATCH_PARTID; > > *flt_val = FIELD_PREP(MSMON_CFG_x_FLT_PARTID, ctx->partid); > + > if (m->ctx->match_pmg) { > *ctl_val |= MSMON_CFG_x_CTL_MATCH_PMG; > *flt_val |= FIELD_PREP(MSMON_CFG_x_FLT_PMG, ctx->pmg); > @@ -972,6 +973,7 @@ static void clean_msmon_ctl_val(u32 *cur_ctl) > static void write_msmon_ctl_flt_vals(struct mon_read *m, u32 ctl_val, > u32 flt_val) > { > + struct msmon_mbwu_state *mbwu_state; > struct mpam_msc *msc = m->ris->vmsc->msc; > > /* > @@ -990,20 +992,32 @@ static void write_msmon_ctl_flt_vals(struct mon_read *m, u32 ctl_val, > mpam_write_monsel_reg(msc, CFG_MBWU_CTL, ctl_val); > mpam_write_monsel_reg(msc, MBWU, 0); > mpam_write_monsel_reg(msc, CFG_MBWU_CTL, ctl_val | MSMON_CFG_x_CTL_EN); > + > + mbwu_state = &m->ris->mbwu_state[m->ctx->mon]; > + if (mbwu_state) > + mbwu_state->prev_val = 0; What's the if condition doing here? The below could make more sense but I don't think you can get here if the allocation fails. if (m->ris->mbwu_state) > + > break; > default: > return; > } > } > > +static u64 mpam_msmon_overflow_val(struct mpam_msc_ris *ris) > +{ > + /* TODO: scaling, and long counters */ > + return GENMASK_ULL(30, 0); > +} > + > /* Call with MSC lock held */ > static void __ris_msmon_read(void *arg) > { > - u64 now; > bool nrdy = false; > struct mon_read *m = arg; > + u64 now, overflow_val = 0; > struct mon_cfg *ctx = m->ctx; > struct mpam_msc_ris *ris = m->ris; > + struct msmon_mbwu_state *mbwu_state; > struct mpam_props *rprops = &ris->props; > struct mpam_msc *msc = m->ris->vmsc->msc; > u32 mon_sel, ctl_val, flt_val, cur_ctl, cur_flt; > @@ -1031,11 +1045,30 @@ static void __ris_msmon_read(void *arg) > now = mpam_read_monsel_reg(msc, CSU); > if (mpam_has_feature(mpam_feat_msmon_csu_hw_nrdy, rprops)) > nrdy = now & MSMON___NRDY; > + now = FIELD_GET(MSMON___VALUE, now); > break; > case mpam_feat_msmon_mbwu: > now = mpam_read_monsel_reg(msc, MBWU); > if (mpam_has_feature(mpam_feat_msmon_mbwu_hw_nrdy, rprops)) > nrdy = now & MSMON___NRDY; > + now = FIELD_GET(MSMON___VALUE, now); > + > + if (nrdy) > + break; > + > + mbwu_state = &ris->mbwu_state[ctx->mon]; > + if (!mbwu_state) > + break; > + > + /* Add any pre-overflow value to the mbwu_state->val */ > + if (mbwu_state->prev_val > now) > + overflow_val = mpam_msmon_overflow_val(ris) - mbwu_state->prev_val; > + > + mbwu_state->prev_val = now; > + mbwu_state->correction += overflow_val; > + > + /* Include bandwidth consumed before the last hardware reset */ > + now += mbwu_state->correction; > break; > default: > m->err = -EINVAL; > @@ -1048,7 +1081,6 @@ static void __ris_msmon_read(void *arg) > return; > } > > - now = FIELD_GET(MSMON___VALUE, now); > *m->val += now; > } > > @@ -1261,6 +1293,67 @@ static int mpam_reprogram_ris(void *_arg) > return 0; > } > > +/* Call with MSC lock held */ > +static int mpam_restore_mbwu_state(void *_ris) > +{ > + int i; > + struct mon_read mwbu_arg; > + struct mpam_msc_ris *ris = _ris; > + > + for (i = 0; i < ris->props.num_mbwu_mon; i++) { > + if (ris->mbwu_state[i].enabled) { > + mwbu_arg.ris = ris; > + mwbu_arg.ctx = &ris->mbwu_state[i].cfg; > + mwbu_arg.type = mpam_feat_msmon_mbwu; > + > + __ris_msmon_read(&mwbu_arg); > + } > + } > + > + return 0; > +} > + > +/* Call with MSC lock and held */ > +static int mpam_save_mbwu_state(void *arg) > +{ > + int i; > + u64 val; > + struct mon_cfg *cfg; > + u32 cur_flt, cur_ctl, mon_sel; > + struct mpam_msc_ris *ris = arg; > + struct msmon_mbwu_state *mbwu_state; > + struct mpam_msc *msc = ris->vmsc->msc; > + > + for (i = 0; i < ris->props.num_mbwu_mon; i++) { > + mbwu_state = &ris->mbwu_state[i]; > + cfg = &mbwu_state->cfg; > + > + if (WARN_ON_ONCE(!mpam_mon_sel_lock(msc))) > + return -EIO; > + > + mon_sel = FIELD_PREP(MSMON_CFG_MON_SEL_MON_SEL, i) | > + FIELD_PREP(MSMON_CFG_MON_SEL_RIS, ris->ris_idx); > + mpam_write_monsel_reg(msc, CFG_MON_SEL, mon_sel); > + > + cur_flt = mpam_read_monsel_reg(msc, CFG_MBWU_FLT); > + cur_ctl = mpam_read_monsel_reg(msc, CFG_MBWU_CTL); > + mpam_write_monsel_reg(msc, CFG_MBWU_CTL, 0); > + > + val = mpam_read_monsel_reg(msc, MBWU); > + mpam_write_monsel_reg(msc, MBWU, 0); > + > + cfg->mon = i; > + cfg->pmg = FIELD_GET(MSMON_CFG_x_FLT_PMG, cur_flt); > + cfg->match_pmg = FIELD_GET(MSMON_CFG_x_CTL_MATCH_PMG, cur_ctl); > + cfg->partid = FIELD_GET(MSMON_CFG_x_FLT_PARTID, cur_flt); > + mbwu_state->correction += val; > + mbwu_state->enabled = FIELD_GET(MSMON_CFG_x_CTL_EN, cur_ctl); > + mpam_mon_sel_unlock(msc); > + } > + > + return 0; > +} > + > static void mpam_init_reset_cfg(struct mpam_config *reset_cfg) > { > memset(reset_cfg, 0, sizeof(*reset_cfg)); > @@ -1335,6 +1428,9 @@ static void mpam_reset_msc(struct mpam_msc *msc, bool online) > * for non-zero partid may be lost while the CPUs are offline. > */ > ris->in_reset_state = online; > + > + if (mpam_is_enabled() && !online) > + mpam_touch_msc(msc, &mpam_save_mbwu_state, ris); > } > } > > @@ -1369,6 +1465,9 @@ static void mpam_reprogram_msc(struct mpam_msc *msc) > mpam_reprogram_ris_partid(ris, partid, cfg); > } > ris->in_reset_state = reset; > + > + if (mpam_has_feature(mpam_feat_msmon_mbwu, &ris->props)) > + mpam_touch_msc(msc, &mpam_restore_mbwu_state, ris); > } > } > > @@ -2091,11 +2190,33 @@ static void mpam_unregister_irqs(void) > > static void __destroy_component_cfg(struct mpam_component *comp) > { > + struct mpam_msc *msc; > + struct mpam_vmsc *vmsc; > + struct mpam_msc_ris *ris; > + > + lockdep_assert_held(&mpam_list_lock); > + > add_to_garbage(comp->cfg); > + list_for_each_entry(vmsc, &comp->vmsc, comp_list) { > + msc = vmsc->msc; > + > + if (mpam_mon_sel_lock(msc)) { > + list_for_each_entry(ris, &vmsc->ris, vmsc_list) > + add_to_garbage(ris->mbwu_state); > + mpam_mon_sel_unlock(msc); > + } > + } > } > > static int __allocate_component_cfg(struct mpam_component *comp) > { > + int err = 0; > + struct mpam_msc *msc; > + struct mpam_vmsc *vmsc; > + struct mpam_msc_ris *ris; > + struct msmon_mbwu_state *mbwu_state; > + > + lockdep_assert_held(&mpam_list_lock); > mpam_assert_partid_sizes_fixed(); > > if (comp->cfg) > @@ -2106,6 +2227,35 @@ static int __allocate_component_cfg(struct mpam_component *comp) > return -ENOMEM; > init_garbage(comp->cfg); > > + list_for_each_entry(vmsc, &comp->vmsc, comp_list) { > + if (!vmsc->props.num_mbwu_mon) > + continue; > + > + msc = vmsc->msc; > + list_for_each_entry(ris, &vmsc->ris, vmsc_list) { > + if (!ris->props.num_mbwu_mon) > + continue; > + > + mbwu_state = kcalloc(ris->props.num_mbwu_mon, > + sizeof(*ris->mbwu_state), > + GFP_KERNEL); > + if (!mbwu_state) { > + __destroy_component_cfg(comp); > + err = -ENOMEM; > + break; > + } > + > + if (mpam_mon_sel_lock(msc)) { > + init_garbage(mbwu_state); > + ris->mbwu_state = mbwu_state; > + mpam_mon_sel_unlock(msc); > + } The if statement is confusing now that mpam_mon_sel_lock() unconditionally returns true. > + } > + > + if (err) > + break; > + } > + > return 0; > } > > diff --git a/drivers/resctrl/mpam_internal.h b/drivers/resctrl/mpam_internal.h > index bb01e7dbde40..725c2aefa8a2 100644 > --- a/drivers/resctrl/mpam_internal.h > +++ b/drivers/resctrl/mpam_internal.h > @@ -212,6 +212,26 @@ struct mon_cfg { > enum mon_filter_options opts; > }; > > +/* > + * Changes to enabled and cfg are protected by the msc->lock. > + * Changes to prev_val and correction are protected by the msc's mon_sel_lock. > + */ > +struct msmon_mbwu_state { > + bool enabled; > + struct mon_cfg cfg; > + > + /* The value last read from the hardware. Used to detect overflow. */ > + u64 prev_val; > + > + /* > + * The value to add to the new reading to account for power management, > + * and shifts to trigger the overflow interrupt. > + */ > + u64 correction; > + > + struct mpam_garbage garbage; > +}; > + > struct mpam_class { > /* mpam_components in this class */ > struct list_head components; > @@ -304,6 +324,9 @@ struct mpam_msc_ris { > /* parent: */ > struct mpam_vmsc *vmsc; > > + /* msmon mbwu configuration is preserved over reset */ > + struct msmon_mbwu_state *mbwu_state; > + > struct mpam_garbage garbage; > }; > Thanks, Ben