On Wed, Dec 10, 2025 at 09:15:18AM -0800, Easwar Hariharan wrote: > On 12/8/2025 9:11 PM, Yu Zhang wrote: > > Add a para-virtualized IOMMU driver for Linux guests running on Hyper-V. > > This driver implements stage-1 IO translation within the guest OS. > > It integrates with the Linux IOMMU core, utilizing Hyper-V hypercalls > > for: > > - Capability discovery > > - Domain allocation, configuration, and deallocation > > - Device attachment and detachment > > - IOTLB invalidation > > > > The driver constructs x86-compatible stage-1 IO page tables in the > > guest memory using consolidated IO page table helpers. This allows > > the guest to manage stage-1 translations independently of vendor- > > specific drivers (like Intel VT-d or AMD IOMMU). > > > > Hyper-v consumes this stage-1 IO page table, when a device domain is > > created and configured, and nests it with the host's stage-2 IO page > > tables, therefore elemenating the VM exits for guest IOMMU mapping > > operations. > > > > For guest IOMMU unmapping operations, VM exits to perform the IOTLB > > flush(and possibly the device TLB flush) is still unavoidable. For > > now, HVCALL_FLUSH_DEVICE_DOMAIN is used to implement a domain-selective > > IOTLB flush. New hypercalls for finer-grained hypercall will be provided > > in future patches. > > > > Co-developed-by: Wei Liu <[email protected]> > > Signed-off-by: Wei Liu <[email protected]> > > Co-developed-by: Jacob Pan <[email protected]> > > Signed-off-by: Jacob Pan <[email protected]> > > Co-developed-by: Easwar Hariharan <[email protected]> > > Signed-off-by: Easwar Hariharan <[email protected]> > > Signed-off-by: Yu Zhang <[email protected]> > > --- > > drivers/iommu/hyperv/Kconfig | 14 + > > drivers/iommu/hyperv/Makefile | 1 + > > drivers/iommu/hyperv/iommu.c | 608 ++++++++++++++++++++++++++++++++++ > > drivers/iommu/hyperv/iommu.h | 53 +++ > > 4 files changed, 676 insertions(+) > > create mode 100644 drivers/iommu/hyperv/iommu.c > > create mode 100644 drivers/iommu/hyperv/iommu.h > > > > <snip> > > > + > > +static int __init hv_iommu_init(void) > > +{ > > + int ret = 0; > > + struct hv_iommu_dev *hv_iommu = NULL; > > + struct hv_output_get_iommu_capabilities hv_iommu_cap = {0}; > > + > > + if (no_iommu || iommu_detected) > > + return -ENODEV; > > + > > + if (!hv_is_hyperv_initialized()) > > + return -ENODEV; > > + > > + if (hv_iommu_detect(&hv_iommu_cap) || > > + !hv_iommu_present(hv_iommu_cap.iommu_cap) || > > + !hv_iommu_s1_domain_supported(hv_iommu_cap.iommu_cap)) > > + return -ENODEV; > > + > > + iommu_detected = 1; > > + pci_request_acs(); > > + > > + hv_iommu = kzalloc(sizeof(*hv_iommu), GFP_KERNEL); > > + if (!hv_iommu) > > + return -ENOMEM; > > + > > + hv_init_iommu_device(hv_iommu, &hv_iommu_cap); > > + > > + ret = hv_initialize_static_domains(); > > + if (ret) { > > + pr_err("hv_initialize_static_domains failed: %d\n", ret); > > + goto err_sysfs_remove; > > This should be goto err_free since we haven't done the sysfs_add yet > > > + } > > + > > + ret = iommu_device_sysfs_add(&hv_iommu->iommu, NULL, NULL, "%s", > > "hv-iommu"); > > + if (ret) { > > + pr_err("iommu_device_sysfs_add failed: %d\n", ret); > > + goto err_free; > > And this should be probably a goto delete_static_domains that cleans up the > allocated static > domains... >
Nice catch. And thanks! :) Yu
