From mboxrd@z Thu Jan 1 00:00:00 1970 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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 6ECECCA5FDD for ; Fri, 2 Oct 2026 18:52:54 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Transfer-Encoding: Content-Type:In-Reply-To:From:References:Cc:To:Subject:MIME-Version:Date: Message-ID:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=nVwF96wxVL8DRKbXKUc9eFh8b5CNJ0VdsZhCPwDx5ag=; b=TorgsTCItSa3axictz7o93g2Kk KwJj/3YtFHLei0fAFcBQm+ZuPdW37mrktO+u8t1gozXaK8O0xgFjv6ppD2RXsKpoIRVhaMcX2dE6L 5JW7Ey1EOZXBEwogWQB80GHhGVCxtrQWB15kX7Xiqrh7B6fkNbzTeJ63cElNJncPg13UYcy2HAAjw uNQhXK4gJVE9OTVg8vYzqRK5kJ7GtYsL0wrgprpBtRyKw3Ga4bX8MBQYYZGgCJbgy6TqCxta5e2oD mkvX/JBlpttm7zGoc08FwPc2SM9ByjZp+cTxTKYLwWXk9WBfOOANngueB2gCuxwoFdGpqa4RQBlE4 iuzpaDcA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1xCiND-0000000CJI1-3bMg; Fri, 02 Oct 2026 18:52:47 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1xCiN4-0000000CJDg-1uWu for linux-arm-kernel@lists.infradead.org; Fri, 02 Oct 2026 18:52:46 +0000 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 1B3B22F; Fri, 2 Oct 2026 11:52:32 -0700 (PDT) Received: from [10.211.55.3] (unknown [10.57.85.177]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id ECC433F86F; Fri, 2 Oct 2026 11:52:33 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1790967155; bh=ysmzAR99tLzKYQ3i8J8rSyoUGfZ735rEhyptVmzCPG0=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=WMImVb64MIy/ghjU1XnaJCS0rry2EvmnCdWbIuPs/1fs9m54PUKywSDITb2cXdGAx lvDM77GU5NbPR3kVHlxa06u7WQoqJqo2aKUG98lZZ0xjJ9okBa6zqdzDX5FYuSdAiB zT4fHGBaIbu+XeM5M35ta5vVEVzP4UMZAKgLdNvs= Message-ID: <28a89543-1199-486b-8de9-54d69a14e723@arm.com> Date: Fri, 2 Oct 2026 19:52:31 +0100 MIME-Version: 1.0 User-Agent: Thunderbird Daily Subject: Re: [PATCH 06/27] arm_mpam: Use __ris_msmon_read() for saving MBWU state To: James Morse , linux-arm-kernel@lists.infradead.org Cc: Catalin Marinas , Will Deacon , Andre Przywara , Fuad Tabba , Gavin Shan References: <20261002173941.292319-1-james.morse@arm.com> <20261002173941.292319-7-james.morse@arm.com> Content-Language: en-US From: Ben Horgan In-Reply-To: <20261002173941.292319-7-james.morse@arm.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20261002_115238_609093_9B385F76 X-CRM114-Status: GOOD ( 28.09 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Hi James, On 02/10/2026 18:39, James Morse wrote: > From: Ben Horgan > > mbwu_save_mbwu_state() reads the MBWU counters and adds that to a saved > correction value. However, the type of counter to read is determined by the > RIS rather than the class and overflow is not taken into account. Fix this > and mitigate against further divergence by using a locked variant of the > same helper used for user monitor reads, __ris_msmon_read(). Using the > locked variant avoids having to drop and retake the mon_sel lock. If the > lock was dropped, an interleaved monitor read which detects overflow would > cause the overflow not to be accounted for in the saved value of > mbwu_state->correction. The correction is no longer updated for disabled > counters but this has no effect as the saved values are not expected to be > useful for disabled counters. > > Fixes: 41e8a14950e1 ("arm_mpam: Track bandwidth counter state for power management") > Signed-off-by: Ben Horgan > Tested-by: Gavin Shan > Reviewed-by: Gavin Shan > [morse: Added comment on correction being included in mpam_save_mbwu_state()] > Reviewed-by: James Morse > Signed-off-by: James Morse > --- > drivers/resctrl/mpam_devices.c | 68 +++++++++++++++++++++++----------- > 1 file changed, 47 insertions(+), 21 deletions(-) > > diff --git a/drivers/resctrl/mpam_devices.c b/drivers/resctrl/mpam_devices.c > index 6df48bec82e2..a3d58a51dc73 100644 > --- a/drivers/resctrl/mpam_devices.c > +++ b/drivers/resctrl/mpam_devices.c > @@ -1029,12 +1029,6 @@ struct mon_read { > bool waited_timeout; > }; > > -static bool mpam_ris_has_mbwu_long_counter(struct mpam_msc_ris *ris) > -{ > - return (mpam_has_feature(mpam_feat_msmon_mbwu_63counter, &ris->props) || > - mpam_has_feature(mpam_feat_msmon_mbwu_44counter, &ris->props)); > -} > - > static u64 mpam_msc_read_mbwu_l(struct mpam_msc *msc) > { > int retry = 3; > @@ -1202,13 +1196,12 @@ static u64 mpam_msmon_overflow_val(enum mpam_device_features type, > return overflow_val; > } > > -static void __ris_msmon_read(void *arg) > +static void __ris_msmon_read_locked(struct mon_read *m) > { > u64 now; > bool nrdy = false; > bool config_mismatch; > bool overflow = false; > - struct mon_read *m = arg; > struct mon_cfg *ctx = m->ctx; > bool reset_on_next_read = false; > struct mpam_msc_ris *ris = m->ris; > @@ -1216,10 +1209,8 @@ static void __ris_msmon_read(void *arg) > struct mpam_msc *msc = m->ris->vmsc->msc; > u32 mon_sel, ctl_val, flt_val, cur_ctl, cur_flt; > > - if (!mpam_mon_sel_lock(msc)) { > - m->err = -EIO; > - return; > - } > + mpam_mon_sel_lock_held(msc); > + > mon_sel = FIELD_PREP(MSMON_CFG_MON_SEL_MON_SEL, ctx->mon) | > FIELD_PREP(MSMON_CFG_MON_SEL_RIS, ris->ris_idx); > mpam_write_monsel_reg(msc, CFG_MON_SEL, mon_sel); > @@ -1312,7 +1303,6 @@ static void __ris_msmon_read(void *arg) > default: > m->err = -EINVAL; > } > - mpam_mon_sel_unlock(msc); > > if (nrdy) > m->err = -EBUSY; > @@ -1323,6 +1313,21 @@ static void __ris_msmon_read(void *arg) > *m->val += now; > } > > +static void __ris_msmon_read(void *arg) > +{ > + struct mon_read *m = arg; > + struct mpam_msc *msc = m->ris->vmsc->msc; > + > + if (!mpam_mon_sel_lock(msc)) { > + m->err = -EIO; > + return; > + } > + > + __ris_msmon_read_locked(m); > + > + mpam_mon_sel_unlock(msc); > +} > + > static int _msmon_read(struct mpam_component *comp, struct mon_read *arg) > { > int err, any_err = 0; > @@ -1674,9 +1679,9 @@ static int mpam_restore_mbwu_state(void *_ris) > > mbwu_state->reset_on_next_read = true; > > - mpam_mon_sel_unlock(msc); > + __ris_msmon_read_locked(&mwbu_arg); > > - __ris_msmon_read(&mwbu_arg); > + mpam_mon_sel_unlock(msc); > } > > return 0; > @@ -1688,10 +1693,12 @@ static int mpam_save_mbwu_state(void *arg) > int i; > u64 val; > struct mon_cfg *cfg; > + struct mon_read mbwu_arg; > 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; > + struct mpam_class *class = ris->vmsc->comp->class; > > for (i = 0; i < ris->props.num_mbwu_mon; i++) { > if (WARN_ON_ONCE(!mpam_mon_sel_lock(msc))) > @@ -1708,17 +1715,36 @@ static int mpam_save_mbwu_state(void *arg) > cur_ctl = mpam_read_monsel_reg(msc, CFG_MBWU_CTL); > mpam_write_monsel_reg(msc, CFG_MBWU_CTL, 0); __ris_msmon_read_locked() checks the _CTL value and reconfigures on mismatch and counters to be lost. This needs to move after the __ris_msmon_read_locked(). > > - if (mpam_ris_has_mbwu_long_counter(ris)) > - val = mpam_msc_read_mbwu_l(msc); > - else > - val = mpam_read_monsel_reg(msc, MBWU); > - > 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); > + > + if (!mbwu_state->enabled) { > + mpam_mon_sel_unlock(msc); > + continue; > + } > + > + val = 0; > + mbwu_arg = (struct mon_read) { > + .ris = ris, > + .ctx = cfg, > + .type = mpam_msmon_choose_counter(class), > + .val = &val, > + }; > + > + __ris_msmon_read_locked(&mbwu_arg); > + > + mbwu_state->reset_on_next_read = true; > + if (!mbwu_arg.err) { > + /* > + * __ris_msmon_read_locked() already included the > + * previous correction value. > + */ > + mbwu_state->correction = val; > + } I'd put it here. Thanks, Ben > + > mpam_mon_sel_unlock(msc); > } >