Hi Jason, Joerg,
Do you have any further comments on this version, particularly
any remaining issues that would warrant a respin before the series
can be considered for inclusion? Thanks a lot!
B.R.
Yu
> This patch series introduces a para-virtualized IOMMU driver for
> Linux guests running on Microsoft Hyper-V. The driver enables two
> primary use cases:
> 1) In-kernel DMA protection for devices assigned to the guest.
> 2) Device assignment to guest user space (e.g., via VFIO).
>
> The driver implements the following core functionality:
> * Hypercall-based Enumeration
> Unlike traditional ACPI-based discovery (e.g., DMAR/IVRS),
> this driver enumerates the Hyper-V IOMMU capabilities directly
> via hypercalls. This approach allows the guest to discover
> IOMMU presence and features without requiring specific virtual
> firmware extensions or modifications.
>
> * Domain Management
> The driver manages IOMMU domains through a new set of Hyper-V
> hypercall interfaces, handling domain allocation and attachment
> for endpoint devices.
>
> * Nested Translation Support
> This implementation leverages guest-managed stage-1 I/O page
> tables nested with host stage-2 translations. It is built
> upon the consolidated IOMMU page table framework (IOMMU_PT).
> This design eliminates the need for emulating map operations.
> Both Intel VT-d and AMD IOMMU platforms are supported.
>
> * IOTLB Invalidation
> IOTLB invalidation requests are marshaled and issued to the
> hypervisor through the same hypercall mechanism. Both domain-
> selective and page-selective flushes are supported.
>
> Implementation Notes:
> * Platform Support
> The current implementation targets x86 platforms with Intel
> VT-d and AMD IOMMU hardware.
>
> * MSI Region Handling
> The standard x86 MSI interrupt range
> (0xfee00000 - 0xfeefffff) is reserved from normal IOVA mappings.
> Future updates may allow this configuration to be queried via
> hypercalls if new hardware platforms are to be supported.
>
> * Reserved Regions (RMRR)
> There is currently no requirement to support assigned devices with
> ACPI RMRR limitations. Consequently, this patch series does not
> specify or query reserved memory regions.
>
> * Guest Hibernation
> Guest hibernation and resume are not supported by this initial
> implementation. The current pvIOMMU interface does not define how
> Hyper-V device-domain objects and device attachments are restored.
>
> Testing:
> Validated with the following configurations:
> - NVMe devices assigned to the guest on AMD platforms, tested
> with fio.
> - Intel DSA devices assigned to the guest, tested with dmatest.
> - dma_map_benchmark for DMA mapping performance evaluation.
>
> Changelog:
>
> v4[1] -> v5:
> - Added Michael Kelley's Reviewed-by tags for patch 1/2/3/4.
>
> - hv: logical device ID registry:
> - Used four-digit hexadecimal values to print PCI domain numbers.
> - Included the PCI domain number in the unregister failure warning.
>
> - iommu/hyperv: para-virtualized IOMMU:
> - Removed the unused per-device endpoint structure, allocation,
> private pointer, and release_device() callback.
> - Clarified the logical device ID lookup failure message.
> - Read the ATS capability from the IOMMU associated with the domain
> instead of the global IOMMU pointer.
>
> - iommu/hyperv: page-selective IOTLB flush:
> - Unified normal and full-range descriptor construction around the
> aligned range start.
> - Used max() to express the minimum Hyper-V page granularity.
> - Reported Hyper-V status values in warnings when the flush fails.
>
> v3[2] -> v4:
> - Added Jacob Pan's Reviewed-by tag for patch 1/4/5.
>
> - hyperv: hypercall interfaces:
> - Added the authoritative Hyper-V type names to imported definitions.
> - Added HV_STATUS_DEVICE_ALREADY_IN_DOMAIN and mapped it to -EEXIST.
>
> - hv: logical device ID registry:
> - Made the registry independent of CONFIG_HYPERV_PVIOMMU.
> - Renamed the APIs to hv_pci_xxx_dev_id(),
> - Reworked initialization and error cleanup to propagate failures.
> - Return -EEXIST with a warning for duplicate registration.
>
> - iommu/x86: architectural MSI reserved region:
> - Replaced the exported range constants with
> iommu_alloc_resv_x86_msi_region().
>
> - iommu/hyperv: para-virtualized IOMMU:
> - Accepted HV_STATUS_DEVICE_ALREADY_IN_DOMAIN as a successful attach,
> and removed the blocking-domain-specific duplicate check.
> - Removed the redundant ATS disable from release_device(); ATS is
> disabled when attaching the release domain.
>
> - iommu/hyperv: page-selective IOTLB flush:
> - Removed the redundant include of linux/hyperv.h.
> - Documented that the list flush also invalidates non-leaf page-walk
> caches before detached page-table pages are freed.
>
> v2[3] -> v3:
> - Added a separate patch defining the common x86 architectural MSI
> reserved range and converted the Intel, AMD, and Hyper-V IOMMU
> drivers to use it.
>
> - hyperv: hypercall interfaces:
> - Used BIT_ULL() for 64-bit capability flags.
> - Matched the create-device-domain input layout to the 32-byte
> Hyper-V ABI.
> - Corrected the page-selective flush range layout to 6/6/52 bits.
>
> - hv: logical device ID registry:
> - Replaced the linear list with an rhashtable for the sparse PCI
> domain number mapping.
> - Used RCU-protected lookup and deferred freeing on removal.
> - Simplified the registration and cleanup paths.
>
> - iommu/hyperv: para-virtualized IOMMU:
> - Renamed the guest driver source to hv-iommu-guest.c.
> - Enabled ATS only after a device-domain attachment succeeds, and
> disabled ATS before attaching the blocking domain.
> - Removed the obsolete deferred-flush capability, unused geometry,
> and redundant device-private-data clearing.
> - Made the Hyper-V domain settings explicit at each caller instead
> of deriving them from the Linux domain type.
> - Added transactional create/configure domain handling with rollback.
> - Required only the base page size and masked the domain page-size
> bitmap with the Hyper-V-supported bitmap.
> - Silenced detection for unsupported hosts while retaining errors
> for actual hypercall and capability failures.
> - Clarified Kconfig support for assigned PCI devices and documented
> the lack of guest hibernation/resume support.
>
> - iommu/hyperv: page-selective IOTLB flush:
> - Removed the inclusive-end overflow and kept the range calculation
> in byte addresses until the final page conversion.
> - Cleared both the fixed hypercall header and the range entry.
> - Warned on selective-flush failure before falling back to a
> full-domain flush.
>
> v1[4] -> v2:
> - Dropped the "move to subdirectory" patch; the directory now exists
> upstream.
>
> - hv: logical device ID registry:
> - Moved the registry to hv_common.c so it can be shared, and derived
> the prefix via a shared helper instead of caching it in pci-hyperv's
> private struct.
> - Moved the lookup out of the irq-disabled region (PREEMPT_RT).
>
> - iommu/hyperv: para-virtualized IOMMU:
> - Removed the unused detach_dev op.
> - Rejected a hypervisor not advertising x86 page sizes instead of
> masking and warning.
> - Statically initialized the identity and blocking domains.
> - Gave the blocking domain its own attach op, which returns the hypercall
> status and WARNs on failure.
>
> - iommu/hyperv: page-selective IOTLB flush:
> - Used a single descriptor covering a slightly larger power-of-two
> range, instead of splitting the range into multiple descriptors.
> - Fixed the inclusive-end corner case in the flush range calculation.
>
> RFC v1[5] -> v1[4]:
> - Scoped platform support to x86 only (Intel VT-d and AMD IOMMU);
> initialization now uses x86_init.iommu.iommu_init
> - Added page-selective IOTLB flush support
> - Disable device ATS in hv_iommu_release_device()
> - Addressed review comments from Michael Kelley:
> - Reversed dependency: pvIOMMU exports registration API for
> pci-hyperv to call, instead of pci-hyperv exporting
> hv_build_logical_dev_id()
> - Dropped separate output page allocation patch; hypercall input
> and output now share the same per-CPU page
> - Cleaned up Kconfig (removed PCI_HYPERV dependency, unnecessary
> selects)
> - Removed dev_list, per-domain spinlock, and syscore_ops
> - Removed forward declarations by reordering functions
> - Fixed typos, cleaned up Kconfig selects, improved pr_info
> messages, etc.
>
> [1] v4:
> https://lore.kernel.org/linux-hyperv/[email protected]/
> [2] v3:
> https://lore.kernel.org/linux-hyperv/[email protected]/
> [3] v2:
> https://lore.kernel.org/linux-hyperv/[email protected]/
> [4] v1:
> https://lore.kernel.org/linux-hyperv/[email protected]/
> [5] RFC v1:
> https://lore.kernel.org/linux-hyperv/[email protected]/
>
> Wei Liu (1):
> hyperv: Introduce new hypercall interfaces used by Hyper-V guest IOMMU
>
> Yu Zhang (4):
> Drivers: hv: Add logical device ID registry for vPCI devices
> iommu/x86: Add architectural MSI reserved region helper
> iommu/hyperv: Add para-virtualized IOMMU support for Hyper-V guest
> iommu/hyperv: Add page-selective IOTLB flush support
>
> arch/x86/hyperv/hv_init.c | 4 +
> arch/x86/include/asm/iommu.h | 14 +
> arch/x86/include/asm/mshyperv.h | 4 +
> drivers/hv/hv_common.c | 115 +++++
> drivers/iommu/Kconfig | 1 +
> drivers/iommu/amd/iommu.c | 6 +-
> drivers/iommu/hyperv/Kconfig | 16 +
> drivers/iommu/hyperv/Makefile | 1 +
> drivers/iommu/hyperv/hv-iommu-guest.c | 679 ++++++++++++++++++++++++++
> drivers/iommu/hyperv/iommu.h | 44 ++
> drivers/iommu/intel/iommu.c | 6 +-
> drivers/pci/controller/pci-hyperv.c | 21 +-
> include/asm-generic/mshyperv.h | 4 +
> include/hyperv/hvgdk_mini.h | 10 +
> include/hyperv/hvhdk_mini.h | 155 ++++++
> include/linux/hyperv.h | 8 +
> 16 files changed, 1073 insertions(+), 15 deletions(-)
> create mode 100644 drivers/iommu/hyperv/Kconfig
> create mode 100644 drivers/iommu/hyperv/hv-iommu-guest.c
> create mode 100644 drivers/iommu/hyperv/iommu.h
>
> --
> 2.52.0
>
