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Wysocki" , Len Brown , James Morse , Ben Horgan , Reinette Chatre , Fenghua Yu , Jonathan Cameron , Srivathsa L Rao , Ganapatrao Kulkarni , Trilok Soni , Srinivas Ramana , Niyas Sait , linux-acpi@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v3 04/16] arm_mpam: propagate MSC read errors for mpam_msc_read_mbwu_l() Message-ID: <20260710114035.00006b0b@oss.qualcomm.com> In-Reply-To: <20260710144520.917375-5-andre.przywara@arm.com> References: <20260710144520.917375-1-andre.przywara@arm.com> <20260710144520.917375-5-andre.przywara@arm.com> Organization: Qualcomm X-Mailer: Claws Mail 4.4.0 (GTK 3.24.51; x86_64-w64-mingw32) Precedence: bulk X-Mailing-List: linux-acpi@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Proofpoint-Spam-Info: AW1haW4tMjYwNzEwMDE4NyBTYWx0ZWRfX/vytJx579k2R UytKwLeaDrzzXEh29UBx8YdiAEboqGM6y2q3tzMAcNMWi8+Vn1JZoaYl9UKCdYq0qF/DpAAG89g oT3Ah3CWhTXH2QtedOqwjJ4CASVD/WU= X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwNzEwMDE4NyBTYWx0ZWRfX56hIkyX9ipOZ Mp6vpNhz2CWe3wy46VFOR/Hf4PS0nhs9Bt1SAw2nKhJ79jFMHI9CqZAi4Tm0+sc5rRL3wsoPNNM 3+3eU/tApyPQCrsgzt9ggN4CaLkox3XdMOIFdnaSVVk8RPMQIvLs4xe3bUd4wCl84Up2ncO7h1b GoQOFL75X7kE1pr699tphtYMIQk+jPjSahE8nGwpQ0kkhfplYw1qniM2sPuFhV0vmd8ugvIhQpV 6bXdYb//yBMNDupId0DRpP+v9MESF+wFCqfOM88MrOcGTpoJ+LTZyx+jNEhnjOe1JnhJIqYiOMQ 4b0Q20LDLi9Xp++0Og+B8oOyKxhLAeAEVjCGw6IqNKyF6Wd/cCAVgFNOOog4Jxa3ss4HjeGGBmX JddscDxmMeXckFM7oyA3EHCDE2byuxOvgJHLDxnDgE6I9CH7dsBNiyDSad//6QYNRYgpBHilLEu LQkTD0OR0DATmTM/WNQ== X-Proofpoint-GUID: QasithLCA1buXvRP1U02r82Exbjr5APK X-Proofpoint-ORIG-GUID: QasithLCA1buXvRP1U02r82Exbjr5APK X-Authority-Analysis: v=2.4 cv=M/x97Sws c=1 sm=1 tr=0 ts=6a513ca8 cx=c_pps a=Oh5Dbbf/trHjhBongsHeRQ==:117 a=qC1CW/w66vtJz1P9yTJxNA==:17 a=kj9zAlcOel0A:10 a=RAioF0-LDSMA:10 a=s4-Qcg_JpJYA:10 a=VkNPw1HP01LnGYTKEx00:22 a=u7WPNUs3qKkmUXheDGA7:22 a=YMgV9FUhrdKAYTUUvYB2:22 a=7CQSdrXTAAAA:8 a=fCQIp7EH0RKNOWKKMFAA:9 a=CjuIK1q_8ugA:10 a=_Vgx9l1VpLgwpw_dHYaR:22 a=a-qgeE7W1pNrGK8U0ZQC:22 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1143,Hydra:6.1.134,FMLib:17.12.100.49 definitions=2026-07-10_05,2026-07-10_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 lowpriorityscore=0 adultscore=0 bulkscore=0 malwarescore=0 suspectscore=0 phishscore=0 spamscore=0 clxscore=1015 priorityscore=1501 impostorscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2606150000 definitions=main-2607100187 On Fri, 10 Jul 2026 16:45:08 +0200 Andre Przywara wrote: > Allow the mpam_msc_read_mbwu_l() function to return an error, and > propagate read errors from the lower level up. > So far we were using a special value to indicate the "unstable read" > condition, replace that with the actual Linux error code, since it's now > easy to do. > > Signed-off-by: Andre Przywara > --- > drivers/resctrl/mpam_devices.c | 54 +++++++++++++++++++++++++--------- > 1 file changed, 40 insertions(+), 14 deletions(-) > > diff --git a/drivers/resctrl/mpam_devices.c b/drivers/resctrl/mpam_devices.c > index b1bd047da203..3b6f9e552a9f 100644 > --- a/drivers/resctrl/mpam_devices.c > +++ b/drivers/resctrl/mpam_devices.c > @@ -1112,8 +1112,9 @@ static bool mpam_ris_has_mbwu_long_counter(struct mpam_msc_ris *ris) > mpam_has_feature(mpam_feat_msmon_mbwu_44counter, &ris->props)); > } > > -static u64 mpam_msc_read_mbwu_l(struct mpam_msc *msc) > +static int mpam_msc_read_mbwu_l(struct mpam_msc *msc, u64 *res) > { > + int ret; > int retry = 3; > u32 mbwu_l_low; > u32 mbwu_l_high1, mbwu_l_high2; > @@ -1123,20 +1124,30 @@ static u64 mpam_msc_read_mbwu_l(struct mpam_msc *msc) > WARN_ON_ONCE((MSMON_MBWU_L + sizeof(u64)) > msc->mapped_hwpage_sz); > WARN_ON_ONCE(!cpumask_test_cpu(smp_processor_id(), &msc->accessibility)); > > - __mpam_read_reg(msc, MSMON_MBWU_L + 4, &mbwu_l_high2); > + ret = __mpam_read_reg(msc, MSMON_MBWU_L + 4, &mbwu_l_high2); > + if (ret) > + return ret; > + > do { > mbwu_l_high1 = mbwu_l_high2; > - __mpam_read_reg(msc, MSMON_MBWU_L, &mbwu_l_low); > - __mpam_read_reg(msc, MSMON_MBWU_L + 4, &mbwu_l_high2); > + ret = __mpam_read_reg(msc, MSMON_MBWU_L, &mbwu_l_low); > + if (ret) > + return ret; > + ret = __mpam_read_reg(msc, MSMON_MBWU_L + 4, &mbwu_l_high2); > + if (ret) > + return ret; > > retry--; > } while (mbwu_l_high1 != mbwu_l_high2 && retry > 0); > > - if (mbwu_l_high1 == mbwu_l_high2) > - return ((u64)mbwu_l_high1 << 32) | mbwu_l_low; > + if (mbwu_l_high1 == mbwu_l_high2) { > + *res = ((u64)mbwu_l_high1 << 32) | mbwu_l_low; > + } else { > + pr_warn("Failed to read a stable value\n"); > + ret = -EBUSY; I guess this may get more complex in later patches, but for now why not just return -EBUSY. > + } > > - pr_warn("Failed to read a stable value\n"); > - return MSMON___L_NRDY; > + return ret; > } > > static void mpam_msc_zero_mbwu_l(struct mpam_msc *msc) > @@ -1283,6 +1294,7 @@ static u64 mpam_msmon_overflow_val(enum mpam_device_features type, > static void __ris_msmon_read(void *arg) > { > u64 now; > + int ret; > u32 now32; > bool nrdy = false; > bool config_mismatch; > @@ -1358,8 +1370,9 @@ static void __ris_msmon_read(void *arg) Relevant bit of context isn't show, but as before looks like ACQUIRE() and ACQUIRE_ERR() will make this simpler by just letting you do direct returns on all error paths though you will need to set m->err = ret in each one. To me that is simpler, but feel free to disagree. > case mpam_feat_msmon_mbwu_44counter: > case mpam_feat_msmon_mbwu_63counter: > if (m->type != mpam_feat_msmon_mbwu_31counter) { > - now = mpam_msc_read_mbwu_l(msc); > - nrdy = now & MSMON___L_NRDY; > + ret = mpam_msc_read_mbwu_l(msc, &now); > + if (ret) > + goto out_unlock; > > if (m->type == mpam_feat_msmon_mbwu_63counter) > now = FIELD_GET(MSMON___LWD_VALUE, now); > @@ -1397,10 +1410,15 @@ static void __ris_msmon_read(void *arg) > if (nrdy) > m->err = -EBUSY; > > - if (m->err) > - return; > + if (!m->err) Above ACQUIRE() suggestion relies on it not being a problem to hold the lock a little longer and incorporate these sets in m. I haven't checked closely but I think that's fine. > + *m->val += now; > + > + return; > + > +out_unlock: > + mpam_mon_sel_unlock(msc); > > - *m->val += now; > + m->err = ret; > } > > static int _msmon_read(struct mpam_component *comp, struct mon_read *arg) > @@ -1747,6 +1765,7 @@ static int mpam_save_mbwu_state(void *arg) > { > int i; > u64 val; > + int ret = 0; > struct mon_cfg *cfg; > u32 cur_flt, cur_ctl, mon_sel; > struct mpam_msc_ris *ris = arg; > @@ -1768,7 +1787,9 @@ static int mpam_save_mbwu_state(void *arg) > mpam_write_monsel_reg(msc, CFG_MBWU_CTL, 0); > > if (mpam_ris_has_mbwu_long_counter(ris)) { > - val = mpam_msc_read_mbwu_l(msc); > + ret = mpam_msc_read_mbwu_l(msc, &val); > + if (ret) > + goto out_unlock; > mpam_msc_zero_mbwu_l(msc); > } else { > u32 val32; > @@ -1788,6 +1809,11 @@ static int mpam_save_mbwu_state(void *arg) > } > > return 0; > + > +out_unlock: > + mpam_mon_sel_unlock(msc); ACQUIRE() would avoid need for this handling so I think this is another good place to look at using it. > + > + return ret; > } > > /*