diff options
Diffstat (limited to 'docs')
| -rw-r--r-- | docs/specs/index.rst | 1 | ||||
| -rw-r--r-- | docs/specs/pci-ids.rst | 2 | ||||
| -rw-r--r-- | docs/specs/riscv-iommu.rst | 90 | ||||
| -rw-r--r-- | docs/system/riscv/virt.rst | 13 |
4 files changed, 106 insertions, 0 deletions
diff --git a/docs/specs/index.rst b/docs/specs/index.rst index 6495ed5ed9..ff5a1f03da 100644 --- a/docs/specs/index.rst +++ b/docs/specs/index.rst @@ -36,3 +36,4 @@ guest hardware that is specific to QEMU. vmgenid rapl-msr rocker + riscv-iommu diff --git a/docs/specs/pci-ids.rst b/docs/specs/pci-ids.rst index 328ab31fe8..261b0f359f 100644 --- a/docs/specs/pci-ids.rst +++ b/docs/specs/pci-ids.rst @@ -98,6 +98,8 @@ PCI devices (other than virtio): PCI ACPI ERST device (``-device acpi-erst``) 1b36:0013 PCI UFS device (``-device ufs``) +1b36:0014 + PCI RISC-V IOMMU device All these devices are documented in :doc:`index`. diff --git a/docs/specs/riscv-iommu.rst b/docs/specs/riscv-iommu.rst new file mode 100644 index 0000000000..463f4cffb6 --- /dev/null +++ b/docs/specs/riscv-iommu.rst @@ -0,0 +1,90 @@ +.. _riscv-iommu: + +RISC-V IOMMU support for RISC-V machines +======================================== + +QEMU implements a RISC-V IOMMU emulation based on the RISC-V IOMMU spec +version 1.0 `iommu1.0`_. + +The emulation includes a PCI reference device, riscv-iommu-pci, that QEMU +RISC-V boards can use. The 'virt' RISC-V machine is compatible with this +device. + +riscv-iommu-pci reference device +-------------------------------- + +This device implements the RISC-V IOMMU emulation as recommended by the section +"Integrating an IOMMU as a PCIe device" of `iommu1.0`_: a PCI device with base +class 08h, sub-class 06h and programming interface 00h. + +As a reference device it doesn't implement anything outside of the specification, +so it uses a generic default PCI ID given by QEMU: 1b36:0014. + +To include the device in the 'virt' machine: + +.. code-block:: bash + + $ qemu-system-riscv64 -M virt -device riscv-iommu-pci,[optional_pci_opts] (...) + +This will add a RISC-V IOMMU PCI device in the board following any additional +PCI parameters (like PCI bus address). The behavior of the RISC-V IOMMU is +defined by the spec but its operation is OS dependent. + +As of this writing the existing Linux kernel support `linux-v8`_, not yet merged, +does not have support for features like VFIO passthrough. The IOMMU emulation +was tested using a public Ventana Micro Systems kernel repository in +`ventana-linux`_. This kernel is based on `linux-v8`_ with additional patches that +enable features like KVM VFIO passthrough with irqbypass. Until the kernel support +is feature complete feel free to use the kernel available in the Ventana Micro Systems +mirror. + +The current Linux kernel support will use the IOMMU device to create IOMMU groups +with any eligible cards available in the system, regardless of factors such as the +order in which the devices are added in the command line. + +This means that these command lines are equivalent as far as the current +IOMMU kernel driver behaves: + +.. code-block:: bash + + $ qemu-system-riscv64 \ + -M virt,aia=aplic-imsic,aia-guests=5 \ + -device riscv-iommu-pci,addr=1.0,vendor-id=0x1efd,device-id=0xedf1 \ + -device e1000e,netdev=net1 -netdev user,id=net1,net=192.168.0.0/24 \ + -device e1000e,netdev=net2 -netdev user,id=net2,net=192.168.200.0/24 \ + (...) + + $ qemu-system-riscv64 \ + -M virt,aia=aplic-imsic,aia-guests=5 \ + -device e1000e,netdev=net1 -netdev user,id=net1,net=192.168.0.0/24 \ + -device e1000e,netdev=net2 -netdev user,id=net2,net=192.168.200.0/24 \ + -device riscv-iommu-pci,addr=1.0,vendor-id=0x1efd,device-id=0xedf1 \ + (...) + +Both will create iommu groups for the two e1000e cards. + +Another thing to notice on `linux-v8`_ and `ventana-linux`_ is that the kernel driver +considers an IOMMU identified as a Rivos device, i.e. it uses Rivos vendor ID. To +use the riscv-iommu-pci device with the existing kernel support we need to emulate +a Rivos PCI IOMMU by setting 'vendor-id' and 'device-id': + +.. code-block:: bash + + $ qemu-system-riscv64 -M virt \ + -device riscv-iommu-pci,vendor-id=0x1efd,device-id=0xedf1 (...) + +Several options are available to control the capabilities of the device, namely: + +- "bus": the bus that the IOMMU device uses +- "ioatc-limit": size of the Address Translation Cache (default to 2Mb) +- "intremap": enable/disable MSI support +- "ats": enable ATS support +- "off" (Out-of-reset translation mode: 'on' for DMA disabled, 'off' for 'BARE' (passthrough)) +- "s-stage": enable s-stage support +- "g-stage": enable g-stage support + +.. _iommu1.0: https://github.com/riscv-non-isa/riscv-iommu/releases/download/v1.0/riscv-iommu.pdf + +.. _linux-v8: https://lore.kernel.org/linux-riscv/cover.1718388908.git.tjeznach@rivosinc.com/ + +.. _ventana-linux: https://github.com/ventanamicro/linux/tree/dev-upstream diff --git a/docs/system/riscv/virt.rst b/docs/system/riscv/virt.rst index 9a06f95a34..8e9a2e4dda 100644 --- a/docs/system/riscv/virt.rst +++ b/docs/system/riscv/virt.rst @@ -84,6 +84,19 @@ none``, as in Firmware images used for pflash must be exactly 32 MiB in size. +riscv-iommu support +------------------- + +The board has support for the riscv-iommu-pci device by using the following +command line: + +.. code-block:: bash + + $ qemu-system-riscv64 -M virt -device riscv-iommu-pci (...) + +Refer to :ref:`riscv-iommu` for more information on how the RISC-V IOMMU support +works. + Machine-specific options ------------------------ |