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[175.34.8.244]) by smtp.gmail.com with ESMTPSA id 5a478bee46e88-3140e6c0702sm6532622eec.22.2026.07.15.21.29.06 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 15 Jul 2026 21:29:09 -0700 (PDT) Message-ID: <8e7f992c-db87-4b79-8d92-d9a44295a0a6@redhat.com> Date: Thu, 16 Jul 2026 14:29:03 +1000 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v1 04/11] arm_mpam: Add missing mon_sel locking in MBWU restore To: Ben Horgan 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: <20260710115546.29644-1-ben.horgan@arm.com> <20260710115546.29644-5-ben.horgan@arm.com> Content-Language: en-US From: Gavin Shan In-Reply-To: <20260710115546.29644-5-ben.horgan@arm.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 7/10/26 9:55 PM, Ben Horgan wrote: > The mon_sel_lock is used to protect the mbwu_state, as well as h/w accesses > that use MPAMCFG_MON_SEL. However, in mpam_restore_mbwu_state() mbwu_state > is accessed without holding the mon_sel_lock. > > Add the missing locking. > > Fixes: 41e8a14950e1 ("arm_mpam: Track bandwidth counter state for power management") > Signed-off-by: Ben Horgan > --- > drivers/resctrl/mpam_devices.c | 8 ++++++++ > 1 file changed, 8 insertions(+) > > diff --git a/drivers/resctrl/mpam_devices.c b/drivers/resctrl/mpam_devices.c > index 11b10c3bc334..b34e2a368516 100644 > --- a/drivers/resctrl/mpam_devices.c > +++ b/drivers/resctrl/mpam_devices.c > @@ -1648,16 +1648,24 @@ static int mpam_restore_mbwu_state(void *_ris) > u64 val; > struct mon_read mwbu_arg; > struct mpam_msc_ris *ris = _ris; > + 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))) > + return -EIO; > + The code can be simplified by avoiding the unnecessary nested conditional statement, something like below: if (!ris->mbwu_state[i].enabled) { mpam_mon_sel_unlock(msc); continue; } mwbu_arg.ris = ris; mwbu_arg.ctx = &ris->mbwu_state[i].cfg; mwbu_arg.type = mpam_msmon_choose_counter(class); mwbu_arg.val = &val; mpam_mon_sel_unlock(msc); __ris_msmon_read(&mwbu_arg); > if (ris->mbwu_state[i].enabled) { > mwbu_arg.ris = ris; > mwbu_arg.ctx = &ris->mbwu_state[i].cfg; > mwbu_arg.type = mpam_msmon_choose_counter(class); > mwbu_arg.val = &val; > > + mpam_mon_sel_unlock(msc); > + > __ris_msmon_read(&mwbu_arg); > + } else { > + mpam_mon_sel_unlock(msc); > } > } > Thanks, Gavin