On Tue, Jul 9, 2024 at 3:37 AM Daniel Henrique Barboza <dbarb...@ventanamicro.com> wrote: > > Add a simple guideline to use the existing RISC-V IOMMU support we just > added. > > This doc will be updated once we add the riscv-iommu-sys device. > > Signed-off-by: Daniel Henrique Barboza <dbarb...@ventanamicro.com> > --- > docs/specs/index.rst | 1 + > docs/specs/riscv-iommu.rst | 55 ++++++++++++++++++++++++++++++++++++++ > docs/system/riscv/virt.rst | 13 +++++++++ > 3 files changed, 69 insertions(+) > create mode 100644 docs/specs/riscv-iommu.rst > > diff --git a/docs/specs/index.rst b/docs/specs/index.rst > index 1484e3e760..c68cd9ae6c 100644 > --- a/docs/specs/index.rst > +++ b/docs/specs/index.rst > @@ -33,3 +33,4 @@ guest hardware that is specific to QEMU. > virt-ctlr > vmcoreinfo > vmgenid > + riscv-iommu > diff --git a/docs/specs/riscv-iommu.rst b/docs/specs/riscv-iommu.rst > new file mode 100644 > index 0000000000..fa38ff7667 > --- /dev/null > +++ b/docs/specs/riscv-iommu.rst > @@ -0,0 +1,55 @@ > +.. _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 [1]. > + > +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. > + > +A platform device that implements the RISC-V IOMMU will be added in the > +future. > + > + > +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 [1]: 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 (...)
We should add a sentence saying what this does. As in what should a user expect after they have done this Alistair > + > +As of this writing the existing Linux kernel support [2], not yet merged, is > being > +created 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" > +- "ioatc-limit" > +- "intremap" > +- "ats" > +- "off" (Out-of-reset translation mode: 'on' for DMA disabled, 'off' for > 'BARE' (passthrough)) > +- "s-stage" > +- "g-stage" > + > + > +[1] > https://github.com/riscv-non-isa/riscv-iommu/releases/download/v1.0/riscv-iommu.pdf > +[2] > https://lore.kernel.org/linux-riscv/cover.1718388908.git.tjezn...@rivosinc.com/ > 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 > ------------------------ > > -- > 2.45.2 > >
