On Wed, Jul 24, 2024 at 10:56 PM Daniel Henrique Barboza <dbarb...@ventanamicro.com> wrote: > > > > On 7/19/24 6:34 AM, Alistair Francis wrote: > > 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 > > I suppose we can add a boilerplate sentence about what an IOMMU does, but > aside > from that I'm not sure what to say about user expectation. If you're adding an > IOMMU (or any device in QEMU) it's expected that the user has some idea of > what > the device is supposed to do in the board and so on hehe
That's fair and I don't think we need to describe what an IOMMU does, I more meant the fact it's attached via PCI. We specifically say a "platform device will be added later" so I think we should just be clear on what a PCI IOMMU is Alistair
