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Sat, 22 Jun 2024 02:05:32 +0000 (GMT) Received: from nalasex01a.na.qualcomm.com (nalasex01a.na.qualcomm.com [10.47.209.196]) by NALASPPMTA04.qualcomm.com (8.17.1.19/8.17.1.19) with ESMTPS id 45M25MQ4024292 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Sat, 22 Jun 2024 02:05:22 GMT Received: from [10.110.82.141] (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; Fri, 21 Jun 2024 19:05:16 -0700 Message-ID: <87c8d5cb-d5b5-ab6c-00d9-bae7f972d777@quicinc.com> Date: Fri, 21 Jun 2024 19:05:14 -0700 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:102.0) Gecko/20100101 Thunderbird/102.11.0 Subject: Re: [RFC PATCH 1/4] drm/msm: register a fault handler for display mmu faults Content-Language: en-US From: Abhinav Kumar To: Dmitry Baryshkov CC: , Rob Clark , "Sean Paul" , Marijn Suijten , "David Airlie" , Daniel Vetter , , , , , , , References: <20240517233801.4071868-1-quic_abhinavk@quicinc.com> <20240517233801.4071868-2-quic_abhinavk@quicinc.com> <355e5bee-a31b-6879-06ea-cf04ba2e179f@quicinc.com> In-Reply-To: <355e5bee-a31b-6879-06ea-cf04ba2e179f@quicinc.com> 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-GUID: 74v68FNFQe1upmBy6tTgZMPpaVYh_G-N X-Proofpoint-ORIG-GUID: 74v68FNFQe1upmBy6tTgZMPpaVYh_G-N X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1039,Hydra:6.0.680,FMLib:17.12.28.16 definitions=2024-06-21_12,2024-06-21_01,2024-05-17_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 suspectscore=0 mlxlogscore=999 spamscore=0 impostorscore=0 adultscore=0 bulkscore=0 mlxscore=0 lowpriorityscore=0 clxscore=1015 malwarescore=0 phishscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.19.0-2406140001 definitions=main-2406220011 On 6/21/2024 4:35 PM, Abhinav Kumar wrote: > > > On 5/19/2024 1:38 AM, Dmitry Baryshkov wrote: >> On Fri, May 17, 2024 at 04:37:56PM -0700, Abhinav Kumar wrote: >>> In preparation to register a iommu fault handler for display >>> related modules, register a fault handler for the backing >>> mmu object of msm_kms. >>> >>> Currently, the fault handler only captures the display snapshot >>> but we can expand this later if more information needs to be >>> added to debug display mmu faults. >>> >>> Signed-off-by: Abhinav Kumar >>> --- >>>   drivers/gpu/drm/msm/msm_kms.c | 25 +++++++++++++++++++++++++ >>>   1 file changed, 25 insertions(+) >>> >>> diff --git a/drivers/gpu/drm/msm/msm_kms.c >>> b/drivers/gpu/drm/msm/msm_kms.c >>> index af6a6fcb1173..62c8e6163e81 100644 >>> --- a/drivers/gpu/drm/msm/msm_kms.c >>> +++ b/drivers/gpu/drm/msm/msm_kms.c >>> @@ -200,6 +200,28 @@ struct msm_gem_address_space >>> *msm_kms_init_aspace(struct drm_device *dev) >>>       return aspace; >>>   } >>> +static int msm_kms_fault_handler(void *arg, unsigned long iova, int >>> flags, void *data) >>> +{ >>> +    struct msm_kms *kms = arg; >>> +    struct msm_disp_state *state; >>> +    int ret; >>> + >>> +    ret = mutex_lock_interruptible(&kms->dump_mutex); >>> +    if (ret) >>> +        return ret; >>> + >>> +    state = msm_disp_snapshot_state_sync(kms); >>> + >>> +    mutex_unlock(&kms->dump_mutex); >>> + >>> +    if (IS_ERR(state)) { >>> +        DRM_DEV_ERROR(kms->dev->dev, "failed to capture snapshot\n"); >>> +        return PTR_ERR(state); >>> +    } >>> + >>> +    return 0; >> >> Hmm, after reading the rest of the code, this means that we won't get >> the error on the console. Could you please change this to -ENOSYS? >> > > I am perhaps missing something here. Are you referring to this > documentation? > >  * Specifically, -ENOSYS is returned if a fault handler isn't installed >  * (though fault handlers can also return -ENOSYS, in case they want to >  * elicit the default behavior of the IOMMU drivers). >  */ > int report_iommu_fault(struct iommu_domain *domain, struct device *dev, >                        unsigned long iova, int flags) > > Doesnt this mean ENOSYS is when fault handler is not installed? > > Because the console print will come if we return 0? > >         if (!report_iommu_fault(ctx->domain, ctx->dev, iova, 0)) { >                 dev_err_ratelimited(ctx->dev, >                                     "Unhandled context fault: fsr=0x%x, " >                                     "iova=0x%016llx, fsynr=0x%x, cb=%d\n", >                                     fsr, iova, fsynr, ctx->asid); >         } > I was checking the wrong place, you are correct. I will return ENOSYS here. Thanks. >>> +} >>> + >>>   void msm_drm_kms_uninit(struct device *dev) >>>   { >>>       struct platform_device *pdev = to_platform_device(dev); >>> @@ -261,6 +283,9 @@ int msm_drm_kms_init(struct device *dev, const >>> struct drm_driver *drv) >>>           goto err_msm_uninit; >>>       } >>> +    if (kms->aspace) >>> +        msm_mmu_set_fault_handler(kms->aspace->mmu, kms, >>> msm_kms_fault_handler); >>> + >>>       drm_helper_move_panel_connectors_to_head(ddev); >>>       drm_for_each_crtc(crtc, ddev) { >>> -- >>> 2.44.0 >>> >>