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Diffstat (limited to 'docs/specs')
| -rw-r--r-- | docs/specs/index.rst | 1 | ||||
| -rw-r--r-- | docs/specs/riscv-aia.rst | 83 | ||||
| -rw-r--r-- | docs/specs/riscv-iommu.rst | 30 |
3 files changed, 111 insertions, 3 deletions
diff --git a/docs/specs/index.rst b/docs/specs/index.rst index ff5a1f03da..d7675cebc2 100644 --- a/docs/specs/index.rst +++ b/docs/specs/index.rst @@ -37,3 +37,4 @@ guest hardware that is specific to QEMU. rapl-msr rocker riscv-iommu + riscv-aia diff --git a/docs/specs/riscv-aia.rst b/docs/specs/riscv-aia.rst new file mode 100644 index 0000000000..8097e2f897 --- /dev/null +++ b/docs/specs/riscv-aia.rst @@ -0,0 +1,83 @@ +.. _riscv-aia: + +RISC-V AIA support for RISC-V machines +====================================== + +AIA (Advanced Interrupt Architecture) support is implemented in the ``virt`` +RISC-V machine for TCG and KVM accelerators. + +The support consists of two main modes: + +- "aia=aplic": adds one or more APLIC (Advanced Platform Level Interrupt Controller) + devices +- "aia=aplic-imsic": adds one or more APLIC device and an IMSIC (Incoming MSI + Controller) device for each CPU + +From an user standpoint, these modes will behave the same regardless of the accelerator +used. From a developer standpoint the accelerator settings will change what it being +emulated in userspace versus what is being emulated by an in-kernel irqchip. + +When running TCG, all controllers are emulated in userspace, including machine mode +(m-mode) APLIC and IMSIC (when applicable). + +When running KVM: + +- no m-mode is provided, so there is no m-mode APLIC or IMSIC emulation regardless of + the AIA mode chosen +- with "aia=aplic", s-mode APLIC will be emulated by userspace +- with "aia=aplic-imsic" there are two possibilities. If no additional KVM option + is provided there will be no APLIC or IMSIC emulation in userspace, and the virtual + machine will use the provided in-kernel APLIC and IMSIC controllers. If the user + chooses to use the irqchip in split mode via "-accel kvm,kernel-irqchip=split", + s-mode APLIC will be emulated while using the s-mode IMSIC from the irqchip + +The following table summarizes how the AIA and accelerator options defines what +we will emulate in userspace: + + +.. list-table:: How AIA and accel options changes controller emulation + :widths: 25 25 25 25 25 25 25 + :header-rows: 1 + + * - Accel + - Accel props + - AIA type + - APLIC m-mode + - IMSIC m-mode + - APLIC s-mode + - IMSIC s-mode + * - tcg + - --- + - aplic + - emul + - n/a + - emul + - n/a + * - tcg + - --- + - aplic-imsic + - emul + - emul + - emul + - emul + * - kvm + - --- + - aplic + - n/a + - n/a + - emul + - n/a + * - kvm + - none + - aplic-imsic + - n/a + - n/a + - in-kernel + - in-kernel + * - kvm + - irqchip=split + - aplic-imsic + - n/a + - n/a + - emul + - in-kernel diff --git a/docs/specs/riscv-iommu.rst b/docs/specs/riscv-iommu.rst index 463f4cffb6..b1538c9ead 100644 --- a/docs/specs/riscv-iommu.rst +++ b/docs/specs/riscv-iommu.rst @@ -6,9 +6,9 @@ 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. +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 -------------------------------- @@ -83,6 +83,30 @@ Several options are available to control the capabilities of the device, namely: - "s-stage": enable s-stage support - "g-stage": enable g-stage support +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: 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/ |