From: Jean-Philippe Brucker <jean-philippe.brucker@arm.com> To: Will Deacon <will@kernel.org> Cc: Mark Rutland <Mark.Rutland@arm.com>, "devicetree@vger.kernel.org" <devicetree@vger.kernel.org>, "jacob.jun.pan@linux.intel.com" <jacob.jun.pan@linux.intel.com>, "joro@8bytes.org" <joro@8bytes.org>, Will Deacon <Will.Deacon@arm.com>, "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>, "eric.auger@redhat.com" <eric.auger@redhat.com>, "iommu@lists.linux-foundation.org" <iommu@lists.linux-foundation.org>, "robh+dt@kernel.org" <robh+dt@kernel.org>, Robin Murphy <Robin.Murphy@arm.com>, "linux-arm-kernel@lists.infradead.org" <linux-arm-kernel@lists.infradead.org> Subject: Re: [PATCH 6/8] iommu/arm-smmu-v3: Support auxiliary domains Date: Fri, 5 Jul 2019 17:29:06 +0100 Message-ID: <7cad065e-5eba-bd22-5c1d-c55ad315ace0@arm.com> (raw) In-Reply-To: <20190626175959.ubxvb2qn4taclact@willie-the-truck> On 26/06/2019 18:59, Will Deacon wrote: >> +static void arm_smmu_aux_detach_dev(struct iommu_domain *domain, struct device *dev) >> +{ >> + struct iommu_domain *parent_domain; >> + struct arm_smmu_domain *parent_smmu_domain; >> + struct arm_smmu_master *master = dev_to_master(dev); >> + struct arm_smmu_domain *smmu_domain = to_smmu_domain(domain); >> + >> + if (!arm_smmu_dev_feature_enabled(dev, IOMMU_DEV_FEAT_AUX)) >> + return; >> + >> + parent_domain = iommu_get_domain_for_dev(dev); >> + if (!parent_domain) >> + return; >> + parent_smmu_domain = to_smmu_domain(parent_domain); >> + >> + mutex_lock(&smmu_domain->init_mutex); >> + if (!smmu_domain->aux_nr_devs) >> + goto out_unlock; >> + >> + if (!--smmu_domain->aux_nr_devs) { >> + arm_smmu_write_ctx_desc(parent_smmu_domain, smmu_domain->ssid, >> + NULL); >> + /* >> + * TLB doesn't need invalidation since accesses from the device >> + * can't use this domain's ASID once the CD is clear. >> + * >> + * Sadly that doesn't apply to ATCs, which are PASID tagged. >> + * Invalidate all other devices as well, because even though >> + * they weren't 'officially' attached to the auxiliary domain, >> + * they could have formed ATC entries. >> + */ >> + arm_smmu_atc_inv_domain(smmu_domain, 0, 0); > > I've been struggling to understand the locking here, since both > arm_smmu_write_ctx_desc and arm_smmu_atc_inv_domain take and release the > devices_lock for the domain. Is there not a problem with devices coming and > going in-between the two calls? Yes it's a problem. I suppose we could take the parent's init_mutex (making sure that it protects detach_dev() as well. First I need to figure out how to prevent the parent domain from disappearing when auxiliary domains are attached, I seem to have forgotten that. I think checking if AUXD is enabled in the device passed to attach_dev() should be sufficient - that's what I do for SVA. But the IOMMU API isn't quite ready to handle failure in iommu_detach_device() at the moment. VFIO will free the domain even if it's still attached. > >> + } else { >> + struct arm_smmu_cmdq_ent cmd; >> + >> + /* Invalidate only this device's ATC */ >> + if (master->ats_enabled) { >> + arm_smmu_atc_inv_to_cmd(smmu_domain->ssid, 0, 0, &cmd); >> + arm_smmu_atc_inv_master(master, &cmd); >> + } >> + } >> +out_unlock: >> + mutex_unlock(&smmu_domain->init_mutex); >> +} >> + >> +static int arm_smmu_aux_get_pasid(struct iommu_domain *domain, struct device *dev) >> +{ >> + struct arm_smmu_domain *smmu_domain = to_smmu_domain(domain); >> + >> + return smmu_domain->ssid ?: -EINVAL; >> +} >> + >> static struct iommu_ops arm_smmu_ops = { >> .capable = arm_smmu_capable, >> .domain_alloc = arm_smmu_domain_alloc, >> @@ -2539,6 +2772,13 @@ static struct iommu_ops arm_smmu_ops = { >> .of_xlate = arm_smmu_of_xlate, >> .get_resv_regions = arm_smmu_get_resv_regions, >> .put_resv_regions = arm_smmu_put_resv_regions, >> + .dev_has_feat = arm_smmu_dev_has_feature, >> + .dev_feat_enabled = arm_smmu_dev_feature_enabled, >> + .dev_enable_feat = arm_smmu_dev_enable_feature, >> + .dev_disable_feat = arm_smmu_dev_disable_feature, > > Why can't we use the existing ->capable and ->dev_{get,set}_attr callbacks > for this? ->capable isn't very useful because it applies to all SMMUs in the system. The existing ->{get,set}_attr callbacks apply to an iommu_domain. The main reason for doing it on endpoints was that it would be tedious to keep track of capabilities when attaching and detaching devices to a domain, especially for drivers that allow multiple IOMMUs per domain [1]. There were more discussions, and in the end Joerg proposed the current API for device attributes [2] [1] https://lore.kernel.org/lkml/aa1ff748-c2ec-acc0-f1d9-cdff2b131e58@linux.intel.com/ [2] https://lore.kernel.org/linux-iommu/20181207102926.GM16835@8bytes.org/ Thanks, Jean _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
next prev parent reply index Thread overview: 43+ messages / expand[flat|nested] mbox.gz Atom feed top 2019-06-10 18:47 [PATCH 0/8] iommu: Add auxiliary domain and PASID support to Arm SMMUv3 Jean-Philippe Brucker 2019-06-10 18:47 ` [PATCH 1/8] iommu: Add I/O ASID allocator Jean-Philippe Brucker 2019-06-11 9:36 ` Jonathan Cameron 2019-06-11 14:35 ` Jean-Philippe Brucker 2019-06-11 18:13 ` Jacob Pan 2019-06-18 14:22 ` Jean-Philippe Brucker 2019-06-18 17:05 ` Jacob Pan 2019-06-19 14:26 ` Jean-Philippe Brucker 2019-06-11 12:26 ` Jacob Pan 2019-06-11 14:37 ` Jean-Philippe Brucker 2019-06-11 17:10 ` Jacob Pan 2019-06-12 11:30 ` Jean-Philippe Brucker 2019-06-10 18:47 ` [PATCH 2/8] dt-bindings: document PASID property for IOMMU masters Jean-Philippe Brucker 2019-07-08 7:58 ` Auger Eric 2019-06-10 18:47 ` [PATCH 3/8] iommu/arm-smmu-v3: Support platform SSID Jean-Philippe Brucker 2019-06-11 9:42 ` Jonathan Cameron 2019-06-11 14:35 ` Jean-Philippe Brucker 2019-06-18 18:08 ` Will Deacon 2019-06-19 11:53 ` Jean-Philippe Brucker 2019-07-08 7:58 ` Auger Eric 2019-09-19 14:51 ` Jean-Philippe Brucker 2019-06-10 18:47 ` [PATCH 4/8] iommu/arm-smmu-v3: Add support for Substream IDs Jean-Philippe Brucker 2019-06-11 10:19 ` Jonathan Cameron 2019-06-11 14:35 ` Jean-Philippe Brucker 2019-06-26 18:00 ` Will Deacon 2019-07-04 9:33 ` Jean-Philippe Brucker 2019-09-19 14:57 ` Jean-Philippe Brucker 2019-07-08 15:31 ` Auger Eric 2019-09-19 15:01 ` Jean-Philippe Brucker 2019-06-10 18:47 ` [PATCH 5/8] iommu/arm-smmu-v3: Add second level of context descriptor table Jean-Philippe Brucker 2019-06-11 10:24 ` Jonathan Cameron 2019-07-08 15:13 ` Auger Eric 2019-06-10 18:47 ` [PATCH 6/8] iommu/arm-smmu-v3: Support auxiliary domains Jean-Philippe Brucker 2019-06-26 17:59 ` Will Deacon 2019-07-05 16:29 ` Jean-Philippe Brucker [this message] 2019-09-19 15:06 ` Jean-Philippe Brucker 2019-06-10 18:47 ` [PATCH 7/8] iommu/arm-smmu-v3: Improve add_device() error handling Jean-Philippe Brucker 2019-07-08 7:58 ` Auger Eric 2019-06-10 18:47 ` [PATCH 8/8] iommu/arm-smmu-v3: Add support for PCI PASID Jean-Philippe Brucker 2019-06-11 10:45 ` Jonathan Cameron 2019-06-11 14:35 ` Jean-Philippe Brucker 2019-07-08 7:58 ` Auger Eric 2019-09-19 15:10 ` Jean-Philippe Brucker
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