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[175.34.8.244]) by smtp.gmail.com with ESMTPSA id a92af1059eb24-13cdc4accf4sm6125716c88.10.2026.07.16.17.53.47 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 16 Jul 2026 17:53:50 -0700 (PDT) Message-ID: <98303800-ff10-4bef-ab2e-7f48b0f6584f@redhat.com> Date: Fri, 17 Jul 2026 10:53:44 +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> <8e7f992c-db87-4b79-8d92-d9a44295a0a6@redhat.com> <33654cc4-9b36-4255-b761-3249174a97d9@arm.com> Content-Language: en-US From: Gavin Shan In-Reply-To: <33654cc4-9b36-4255-b761-3249174a97d9@arm.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Hi Ben, On 7/16/26 7:31 PM, Ben Horgan wrote: > On 7/16/26 05:29, Gavin Shan wrote: >> 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); >>>           } >>>       } >>> > > Ok. I think it will be clearer what's best here once Andre's error propagation in his MPAM-Fb series > has crystalized. > Yeah, we can clean this up after that. > Thanks, > > Ben > Thanks, Gavin