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 27682341650 for ; Wed, 15 Jul 2026 08:45:03 +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=1784105109; cv=none; b=sC/fOTvbMwti36p3EVICRAicG1LPdN2RHGynA6Bw+O9nLvGnTbaZ6i3oGCW6qkyGqyDDgsyP1FtJe/PYOzD3OJX/224i+QL32wfQsvD14HC+R28VXKJW8+LcLs+6Usnv6kleYrMDFUMichZDYqitZmrALykoO9ycBdV+Fz+2Lvw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784105109; c=relaxed/simple; bh=1sybEJPLAgbVvCjAlxeTEX9l41vo0Yb+Tru9FMaLLEk=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=eEBM5aKFpCVIDZVoFN23sPcuVOXk0O5qXFdyxYegEeslJGI1XNGCjsVfXL7oV5RQkHuXJgBwBijz0tDD2cHvuK67CndYXd402zswKu++9VmCWbd66Cs2o9Q3Xcf99ozvMeS5E8ni9RegJL+rED9PbMjWof5Fm8gGkpbHpAf3s6Y= 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; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b=a5elHshe; 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 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b="a5elHshe" 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 184971477; Wed, 15 Jul 2026 01:44:58 -0700 (PDT) Received: from [10.2.212.8] (e134344.arm.com [10.2.212.8]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 645093F7B4; Wed, 15 Jul 2026 01:45:01 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1784105102; bh=1sybEJPLAgbVvCjAlxeTEX9l41vo0Yb+Tru9FMaLLEk=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=a5elHshe13Z3UYuuG+sinQcs9xh5UvkOv/ogchW3GTpTfE1x/vtDGaMFIl5ZLz7E7 Z9NQbWHtL2l4FtMVnsfbc7MUjZEbR/Xl+zOtpa7d4BVA1YQ41AewLse/NC2V4vFpav EhqXlmB2+nsbtVOtLMCL72DomM32+IIUVxsanqsE= Message-ID: <0e4246f2-bcfc-4b08-9361-e87872c23672@arm.com> Date: Wed, 15 Jul 2026 09:45:00 +0100 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Thunderbird Daily Subject: Re: [PATCH v1 05/11] arm_mpam: Ensure MBWU counters are reset on restore To: "Shaopeng Tan (Fujitsu)" Cc: "james.morse@arm.com" , "reinette.chatre@intel.com" , "fenghuay@nvidia.com" , "linux-kernel@vger.kernel.org" , "linux-arm-kernel@lists.infradead.org" , "dave.martin@arm.com" , "andre.przywara@arm.com" References: <20260710115546.29644-6-ben.horgan@arm.com> Content-Language: en-US From: Ben Horgan In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Hi Shaopeng, On 7/15/26 08:49, Shaopeng Tan (Fujitsu) wrote: > Hello Ben, > >> When an MSC becomes inaccessible due to cpu offline CFG_MBWU_CTL is set to >> zero in mpam_save_mbwu_state(). This is very likely to mean that the config >> will mismatch when restoring and so the monitor will be reset. However, the >> state may have been lost and so there are no guarantees. Ensure the reset >> happens by setting the reset_on_next_read and remove the unnecessary writes >>from mpam_save_mbwu_state(). >> >> Fixes: 41e8a14950e1 ("arm_mpam: Track bandwidth counter state for power management") >> Signed-off-by: Ben Horgan >> --- >>  drivers/resctrl/mpam_devices.c | 13 +++++++------ >>  1 file changed, 7 insertions(+), 6 deletions(-) >> >> diff --git a/drivers/resctrl/mpam_devices.c b/drivers/resctrl/mpam_devices.c >> index b34e2a368516..222fc248067e 100644 >> --- a/drivers/resctrl/mpam_devices.c >> +++ b/drivers/resctrl/mpam_devices.c >> @@ -1648,10 +1648,13 @@ static int mpam_restore_mbwu_state(void *_ris) >>          u64 val; >>          struct mon_read mwbu_arg; >>          struct mpam_msc_ris *ris = _ris; >> +       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++) { >> +               mbwu_state = &ris->mbwu_state[i]; >> + >>                  if (WARN_ON_ONCE(!mpam_mon_sel_lock(msc))) >>                          return -EIO; >>   >> @@ -1661,6 +1664,8 @@ static int mpam_restore_mbwu_state(void *_ris) >>                          mwbu_arg.type = mpam_msmon_choose_counter(class); >>                          mwbu_arg.val = &val; >>   >> +                       mbwu_state->reset_on_next_read = true; >> + >>                          mpam_mon_sel_unlock(msc); > > for (i = 0; i < ris->props.num_mbwu_mon; i++) { > + mbwu_state = &ris->mbwu_state[i]; > + > if (WARN_ON_ONCE(!mpam_mon_sel_lock(msc))) > return -EIO; > > - if (ris->mbwu_state[i].enabled) { > + if (mbwu_state->enabled) { //this line might need refactoring I'm unclear on what you are trying to point out in this email. Please can you explain. Thanks, Ben > mwbu_arg.ris = ris; > - mwbu_arg.ctx = &ris->mbwu_state[i].cfg; > + mwbu_arg.ctx = &mbwu_state->cfg; //and this line > mwbu_arg.type = mpam_msmon_choose_counter(class); > mwbu_arg.val = &val; > > + mbwu_state->reset_on_next_read = true; > + > mpam_mon_sel_unlock(msc); > > > Best regards, > Shaopeng TAN > >>                          __ris_msmon_read(&mwbu_arg); >> @@ -1696,15 +1701,11 @@ static int mpam_save_mbwu_state(void *arg) >>   >>                  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); >>   >> -               if (mpam_ris_has_mbwu_long_counter(ris)) { >> +               if (mpam_ris_has_mbwu_long_counter(ris)) >>                          val = mpam_msc_read_mbwu_l(msc); >> -                       mpam_msc_zero_mbwu_l(msc); >> -               } else { >> +               else >>                          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); >> -- >> 2.43.0