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[35.198.224.169]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2230a095f02sm16558235ad.152.2025.02.25.08.47.52 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 25 Feb 2025 08:47:57 -0800 (PST) Date: Tue, 25 Feb 2025 16:47:47 +0000 From: Pranjal Shrivastava To: Nicolin Chen Cc: jgg@nvidia.com, kevin.tian@intel.com, corbet@lwn.net, will@kernel.org, joro@8bytes.org, suravee.suthikulpanit@amd.com, robin.murphy@arm.com, dwmw2@infradead.org, baolu.lu@linux.intel.com, shuah@kernel.org, linux-kernel@vger.kernel.org, iommu@lists.linux.dev, linux-arm-kernel@lists.infradead.org, linux-kselftest@vger.kernel.org, linux-doc@vger.kernel.org, eric.auger@redhat.com, jean-philippe@linaro.org, mdf@kernel.org, mshavit@google.com, shameerali.kolothum.thodi@huawei.com, smostafa@google.com, ddutile@redhat.com, yi.l.liu@intel.com, patches@lists.linux.dev Subject: Re: [PATCH v7 13/14] iommu/arm-smmu-v3: Report events that belong to devices attached to vIOMMU Message-ID: References: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Mon, Feb 24, 2025 at 01:56:46PM -0800, Nicolin Chen wrote: > On Mon, Feb 24, 2025 at 09:35:14PM +0000, Pranjal Shrivastava wrote: > > On Sat, Feb 22, 2025 at 07:54:10AM -0800, Nicolin Chen wrote: > > > +int arm_vmaster_report_event(struct arm_smmu_vmaster *vmaster, u64 *evt) > > > +{ > > > + struct iommu_vevent_arm_smmuv3 vevt; > > > + int i; > > > + > > > + lockdep_assert_held(&vmaster->vsmmu->smmu->streams_mutex); > > > + > > > + vevt.evt[0] = cpu_to_le64((evt[0] & ~EVTQ_0_SID) | > > > + FIELD_PREP(EVTQ_0_SID, vmaster->vsid)); > > > + for (i = 1; i < EVTQ_ENT_DWORDS; i++) > > > + vevt.evt[i] = cpu_to_le64(evt[i]); > > > > Just thinking out loud here: > > I understand the goal here is to "emulate" an IOMMU. But I'm just > > wondering if we could report struct events instead of the raw event? > > > > For example, can't we have something like arm_smmu_event here with the > > sid changed to vsid? > > > > Are we taking the raw event since we want to keep the `u64 event_data[]` > > field within `struct iommufd_vevent` generic to all architectures? > > The ABIs for vSMMU are defined in the HW languange, e.g. cmd, ste. > Thus, here evt in raw too. > Ack. Makes sense. > > > - ret = iommu_report_device_fault(master->dev, &fault_evt); > > > + if (event->stall) { > > > + ret = iommu_report_device_fault(master->dev, &fault_evt); > > > + } else { > > > + if (master->vmaster && !event->s2) > > > + ret = arm_vmaster_report_event(master->vmaster, evt); > > > + else > > > + ret = -EFAULT; /* Unhandled events should be pinned */ > > > + } > > > > Nit: > > I don't see the `arm_smmu_handle_event` being called elsewhere, is there > > a reason to return -EFAULT instead of -EOPNOTSUPP here? > > > > I think the current behavior here is to return -EOPNOTSUPP if (!event->stall). > > Whereas, what we're doing here is: > > if (event->stall) { > > ... > > /* do legacy stuff */ > > ... > > } > > > > else { > > if (master->vmaster && !event->s2) > > arm_vmaster_report_event(vmaster, evt); > > else > > ret = -EFAULT > > } > > > > mutex_unlock(&smmu->streams_mutex); > > return ret; > > > > Thus, we end up returning -EFAULT instead of -EOPNOTSUPP in case > > event->stall == false. I agree that we aren't really checking the return > > value in the evtq_thread handler, but I'm wondering if we should ensure > > that we end up retaining the same behaviour as we have right now? > > Oh, it looks like -EOPNOTSUPP should be returned here. Will fix. > With the fix to return `-EOPNOTSUPP`: Reviewed-by: Pranjal Shrivastava Thanks, Praan