mirror of
https://github.com/qemu/qemu.git
synced 2026-07-08 17:46:17 +00:00
ad2a0aa282
The iommu Linux kernel support is now upstream. VFIO is still downstream at this stage. Reviewed-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com> Signed-off-by: Joel Stanley <joel@jms.id.au> Message-ID: <20250814001452.504510-1-joel@jms.id.au> Signed-off-by: Alistair Francis <alistair.francis@wdc.com>
108 lines
4.0 KiB
ReStructuredText
108 lines
4.0 KiB
ReStructuredText
.. _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 `iommu1.0.0`_.
|
|
|
|
The emulation includes a PCI reference device (riscv-iommu-pci) and a platform
|
|
bus device (riscv-iommu-sys) that QEMU RISC-V boards can use. The 'virt'
|
|
RISC-V machine is compatible with both devices.
|
|
|
|
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 `iommu1.0.0`_: 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.
|
|
|
|
Linux kernel iommu support was merged in v6.13. QEMU IOMMU emulation can be
|
|
used with mainline kernels for simple IOMMU PCIe support.
|
|
|
|
As of v6.17, it does not have support for features like VFIO passthrough.
|
|
There is a `VFIO`_ RFC series that is not yet merged. The public Ventana Micro
|
|
Systems kernel repository in `ventana-linux`_ can be used for testing the VFIO
|
|
functions.
|
|
|
|
The v6.13+ Linux kernel support uses 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 \
|
|
-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=3.0 \
|
|
(...)
|
|
|
|
Both will create iommu groups for the two e1000e cards.
|
|
|
|
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
|
|
- "hpm-counters": number of hardware performance counters available. Maximum value is 31.
|
|
Default value is 31. Use 0 (zero) to disable HPM support
|
|
- "vendor-id"/"device-id": pci device ID. Defaults to 1b36:0014 (Redhat)
|
|
|
|
riscv-iommu-sys device
|
|
----------------------
|
|
|
|
This device implements the RISC-V IOMMU emulation as a platform bus device that
|
|
RISC-V boards can use.
|
|
|
|
For the 'virt' board the device is disabled by default. To enable it use the
|
|
'iommu-sys' machine option:
|
|
|
|
.. code-block:: bash
|
|
|
|
$ qemu-system-riscv64 -M virt,iommu-sys=on (...)
|
|
|
|
There is no options to configure the capabilities of this device in the 'virt'
|
|
board using the QEMU command line. The device is configured with the following
|
|
riscv-iommu options:
|
|
|
|
- "ioatc-limit": default value (2Mb)
|
|
- "intremap": enabled
|
|
- "ats": enabled
|
|
- "off": on (DMA disabled)
|
|
- "s-stage": enabled
|
|
- "g-stage": enabled
|
|
|
|
.. _iommu1.0.0: https://github.com/riscv-non-isa/riscv-iommu/releases/download/v1.0.0/riscv-iommu.pdf
|
|
|
|
.. _VFIO: https://lore.kernel.org/linux-riscv/20241114161845.502027-17-ajones@ventanamicro.com/
|
|
|
|
.. _ventana-linux: https://github.com/ventanamicro/linux/tree/dev-upstream
|