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Wed, 08 Jan 2025 01:34:21 +0000 (GMT) Received: from nalasex01a.na.qualcomm.com (nalasex01a.na.qualcomm.com [10.47.209.196]) by NALASPPMTA04.qualcomm.com (8.18.1.2/8.18.1.2) with ESMTPS id 5081YLAU031224 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Wed, 8 Jan 2025 01:34:21 GMT Received: from [10.134.71.247] (10.80.80.8) by nalasex01a.na.qualcomm.com (10.47.209.196) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1544.9; Tue, 7 Jan 2025 17:34:20 -0800 Message-ID: <842c9230-d95a-43b8-83ed-0bfb286ee334@quicinc.com> Date: Tue, 7 Jan 2025 17:34:20 -0800 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 v2 5/5] drm/msm/dpu: rate limit snapshot capture for mmu faults To: Jessica Zhang , Dmitry Baryshkov CC: Rob Clark , Sean Paul , "Marijn Suijten" , David Airlie , Simona Vetter , , , , References: <20241217-abhinavk-smmu-fault-handler-v2-0-451377666cad@quicinc.com> <20241217-abhinavk-smmu-fault-handler-v2-5-451377666cad@quicinc.com> Content-Language: en-US From: Abhinav Kumar In-Reply-To: Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 8bit X-ClientProxiedBy: nasanex01b.na.qualcomm.com (10.46.141.250) To nalasex01a.na.qualcomm.com (10.47.209.196) X-QCInternal: smtphost X-Proofpoint-Virus-Version: vendor=nai engine=6200 definitions=5800 signatures=585085 X-Proofpoint-ORIG-GUID: WXqXdxY5x0QJGiQ2Mmgfz4GIO1czaNLf X-Proofpoint-GUID: WXqXdxY5x0QJGiQ2Mmgfz4GIO1czaNLf X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1039,Hydra:6.0.680,FMLib:17.12.60.29 definitions=2024-09-06_09,2024-09-06_01,2024-09-02_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 impostorscore=0 clxscore=1015 spamscore=0 bulkscore=0 malwarescore=0 adultscore=0 mlxlogscore=999 suspectscore=0 lowpriorityscore=0 phishscore=0 mlxscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.19.0-2411120000 definitions=main-2501080009 On 12/18/2024 1:33 PM, Jessica Zhang wrote: > > > On 12/18/2024 3:20 AM, Dmitry Baryshkov wrote: >> On Tue, Dec 17, 2024 at 04:27:57PM -0800, Jessica Zhang wrote: >>> From: Abhinav Kumar >>> >>> There is no recovery mechanism in place yet to recover from mmu >>> faults for DPU. We can only prevent the faults by making sure there >>> is no misconfiguration. >>> >>> Rate-limit the snapshot capture for mmu faults to once per >>> msm_atomic_commit_tail() as that should be sufficient to capture >>> the snapshot for debugging otherwise there will be a lot of DPU >>> snapshots getting captured for the same fault which is redundant >>> and also might affect capturing even one snapshot accurately. >>> >>> Signed-off-by: Abhinav Kumar >>> Signed-off-by: Jessica Zhang >>> --- >>>   drivers/gpu/drm/msm/msm_atomic.c | 2 ++ >>>   drivers/gpu/drm/msm/msm_kms.c    | 5 ++++- >>>   drivers/gpu/drm/msm/msm_kms.h    | 3 +++ >>>   3 files changed, 9 insertions(+), 1 deletion(-) >>> >>> diff --git a/drivers/gpu/drm/msm/msm_atomic.c >>> b/drivers/gpu/drm/msm/msm_atomic.c >>> index >>> 9c45d641b5212c11078ab38c13a519663d85e10a..9ad7eeb14d4336abd9d8a8eb1382bdddce80508a 100644 >>> --- a/drivers/gpu/drm/msm/msm_atomic.c >>> +++ b/drivers/gpu/drm/msm/msm_atomic.c >>> @@ -228,6 +228,8 @@ void msm_atomic_commit_tail(struct >>> drm_atomic_state *state) >>>       if (kms->funcs->prepare_commit) >>>           kms->funcs->prepare_commit(kms, state); >>> +    kms->fault_snapshot_capture = 0; >>> + >> >> - Please move it before the prepare_commit(). >> - You are accessing the same variable from different threads / cores. >>    There should be some kind of a sync barrier. > > Hi Dmitry, > > Ack, will add a lock for the snapshot capture counter. > > Thanks, > > Jessica Zhang > We cannot have a mutex lock because msm_kms_fault_handler cannot hold a mutex. So we need an atomic variable in this case. >> >>>       /* >>>        * Push atomic updates down to hardware: >>>        */ >>> diff --git a/drivers/gpu/drm/msm/msm_kms.c >>> b/drivers/gpu/drm/msm/msm_kms.c >>> index >>> 78830e446355f77154fa21a5d107635bc88ba3ed..3327caf396d4fc905dc127f09515559c12666dc8 100644 >>> --- a/drivers/gpu/drm/msm/msm_kms.c >>> +++ b/drivers/gpu/drm/msm/msm_kms.c >>> @@ -168,7 +168,10 @@ static int msm_kms_fault_handler(void *arg, >>> unsigned long iova, int flags, void >>>   { >>>       struct msm_kms *kms = arg; >>> -    msm_disp_snapshot_state(kms->dev); >>> +    if (!kms->fault_snapshot_capture) { >>> +        msm_disp_snapshot_state(kms->dev); >>> +        kms->fault_snapshot_capture++; >>> +    } >>>       return -ENOSYS; >>>   } >>> diff --git a/drivers/gpu/drm/msm/msm_kms.h >>> b/drivers/gpu/drm/msm/msm_kms.h >>> index >>> e60162744c669773b6e5aef824a173647626ab4e..3ac089e26e14b824567f3cd2c62f82a1b9ea9878 100644 >>> --- a/drivers/gpu/drm/msm/msm_kms.h >>> +++ b/drivers/gpu/drm/msm/msm_kms.h >>> @@ -128,6 +128,9 @@ struct msm_kms { >>>       int irq; >>>       bool irq_requested; >>> +    /* rate limit the snapshot capture to once per attach */ >>> +    int fault_snapshot_capture; >>> + >>>       /* mapper-id used to request GEM buffer mapped for scanout: */ >>>       struct msm_gem_address_space *aspace; >>> >>> -- >>> 2.34.1 >>> >> >> -- >> With best wishes >> Dmitry >