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[47.54.130.67]) by smtp.gmail.com with ESMTPSA id 6a1803df08f44-8f472a9ad1fsm58402856d6.47.2026.07.03.10.32.48 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 03 Jul 2026 10:32:48 -0700 (PDT) Received: from jgg by wakko with local (Exim 4.97) (envelope-from ) id 1wfhku-00000008Ink-0GPL; Fri, 03 Jul 2026 14:32:48 -0300 Date: Fri, 3 Jul 2026 14:32:48 -0300 From: Jason Gunthorpe To: Yu Zhang Cc: linux-kernel@vger.kernel.org, linux-hyperv@vger.kernel.org, iommu@lists.linux.dev, linux-pci@vger.kernel.org, linux-arch@vger.kernel.org, wei.liu@kernel.org, kys@microsoft.com, haiyangz@microsoft.com, decui@microsoft.com, longli@microsoft.com, joro@8bytes.org, will@kernel.org, robin.murphy@arm.com, bhelgaas@google.com, kwilczynski@kernel.org, lpieralisi@kernel.org, mani@kernel.org, robh@kernel.org, arnd@arndb.de, mhklinux@outlook.com, jacob.pan@linux.microsoft.com, tgopinath@linux.microsoft.com, easwar.hariharan@linux.microsoft.com, mrathor@linux.microsoft.com Subject: Re: [PATCH v2 3/4] iommu/hyperv: Add para-virtualized IOMMU support for Hyper-V guest Message-ID: <20260703173248.GB1968184@ziepe.ca> References: <20260702160518.311234-1-zhangyu1@linux.microsoft.com> <20260702160518.311234-4-zhangyu1@linux.microsoft.com> Precedence: bulk X-Mailing-List: linux-arch@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: <20260702160518.311234-4-zhangyu1@linux.microsoft.com> On Fri, Jul 03, 2026 at 12:05:17AM +0800, Yu Zhang wrote: > +static bool hv_iommu_capable(struct device *dev, enum iommu_cap cap) > +{ > + switch (cap) { > + case IOMMU_CAP_CACHE_COHERENCY: > + return true; > + case IOMMU_CAP_DEFERRED_FLUSH: > + return true; This CAP isn't necessary anymore > +static struct iommu_device *hv_iommu_probe_device(struct device *dev) > +{ > + struct pci_dev *pdev; > + struct hv_iommu_endpoint *vdev; > + struct hv_output_get_logical_device_property device_iommu_property = {0}; > + > + if (!dev_is_pci(dev)) > + return ERR_PTR(-ENODEV); > + > + pdev = to_pci_dev(dev); > + > + if (hv_iommu_get_logical_device_property(dev, > + HV_LOGICAL_DEVICE_PROPERTY_PVIOMMU, > + &device_iommu_property) || > + !(device_iommu_property.device_iommu & HV_DEVICE_IOMMU_ENABLED)) > + return ERR_PTR(-ENODEV); > + > + vdev = kzalloc_obj(*vdev, GFP_KERNEL); > + if (!vdev) > + return ERR_PTR(-ENOMEM); > + > + vdev->dev = dev; > + vdev->hv_iommu = hv_iommu_device; > + dev_iommu_priv_set(dev, vdev); > + > + if (hv_iommu_ats_supported(hv_iommu_device->cap) && > + pci_ats_supported(pdev)) > + pci_enable_ats(pdev, __ffs(hv_iommu_device->pgsize_bitmap)); This can probably just be PAGE_SHIFT Also ATS shouldn't be enabled until a translation is installed, otherwise the driver cannot participate in the ATS error handling Nicolin is working on. > +static void hv_iommu_release_device(struct device *dev) > +{ > + struct hv_iommu_endpoint *vdev = dev_iommu_priv_get(dev); > + struct pci_dev *pdev = to_pci_dev(dev); > + > + if (pdev->ats_enabled) > + pci_disable_ats(pdev); > + > + dev_iommu_priv_set(dev, NULL); No necessary, the caller does it > +static struct iommu_group *hv_iommu_device_group(struct device *dev) > +{ > + if (dev_is_pci(dev)) > + return pci_device_group(dev); > + > + WARN_ON_ONCE(1); > + return generic_device_group(dev); I think you can just return failure here instead of WARN_ON ? > +static int __init hv_initialize_static_domains(void) > +{ > + int ret; > + struct hv_iommu_domain *hv_domain; > + > + /* Default stage-1 identity domain */ > + hv_domain = &hv_identity_domain; > + > + ret = hv_create_device_domain(hv_domain, HV_DEVICE_DOMAIN_TYPE_S1); > + if (ret) > + return ret; > + > + ret = hv_configure_device_domain(hv_domain, IOMMU_DOMAIN_IDENTITY); > + if (ret) > + goto delete_identity_domain; IMHO I would change this around to have a single function that accepts a struct hv_input_configure_device_domain as input and does both of the hypercalls inside. Then here it is easy to directly construct the hv_input_configure_device_domain for blocking and identity. I'd be happy if this never touched domain_type, drivers shouldn't be touching that. > +static void __init hv_init_iommu_device(struct hv_iommu_dev *hv_iommu, > + struct hv_output_get_iommu_capabilities *hv_iommu_cap) > +{ > + ida_init(&hv_iommu->domain_ids); > + > + hv_iommu->cap = hv_iommu_cap->iommu_cap; > + hv_iommu->max_iova_width = hv_iommu_cap->max_iova_width; > + if (!hv_iommu_5lvl_supported(hv_iommu->cap) && > + hv_iommu->max_iova_width > 48) { > + pr_info("5-level paging not supported, limiting iova width to 48.\n"); > + hv_iommu->max_iova_width = 48; > + } > + > + hv_iommu->geometry = (struct iommu_domain_geometry) { > + .aperture_start = 0, > + .aperture_end = (((u64)1) << hv_iommu->max_iova_width) - 1, > + .force_aperture = true, > + }; I don't see anything reading this, I don't expect this to be used? The max_iova_width has to be passed into the iommupt creation, which it does: + cfg.common.hw_max_vasz_lg2 = hv_iommu_device->max_iova_width; + cfg.common.hw_max_oasz_lg2 = 52; + cfg.top_level = (hv_iommu_device->max_iova_width > 48) ? 4 : 3; + ret = pt_iommu_x86_64_init(&hv_domain->pt_iommu_x86_64, &cfg, GFP_KERNEL); + if (ret) So just delete hv->iommu->geometry. Also, VT-D has weirdness where the HW can require a 4 level table but only a 3 level worth of IOVA width is being used. This was a real-world bug we hit when converting to iommupt. This interaction with the HV doesn't seem able to represent that. > + /* > + * The page table code only maps x86 page sizes (4K/2M/1G); require the > + * hypervisor to advertise a non-empty subset of exactly those. > + */ > + if (!hv_iommu_cap.pgsize_bitmap || > + (hv_iommu_cap.pgsize_bitmap & ~(u64)(SZ_4K | SZ_2M | SZ_1G))) { > + pr_err("unsupported page sizes: pgsize_bitmap=0x%llx\n", > + hv_iommu_cap.pgsize_bitmap); > + return -ENODEV; > + } This can just be if (!(hv_iommu_cap.pgsize_bitmap & PAGE_SHIFT)) { pr_err("unsupported page sizes: pgsize_bitmap=0x%llx\n", hv_iommu_cap.pgsize_bitmap); } return -ENODEV; Which is all you really need. If the HV doesn't support 1G it is perfectly fine, the iommupt page bitmap is already masked by this. > + ret = iommu_device_register(&hv_iommu->iommu, &hv_iommu_ops, NULL); > + if (ret) { > + pr_err("iommu_device_register failed: %d\n", ret); > + goto err_sysfs_remove; > + } > + > + pr_info("successfully initialized\n"); Don't log someting so vauge? Jason