Merge tag 'pull-riscv-to-apply-20241031-1' of https://github.com/alistair23/qemu into staging

RISC-V PR for 9.2

* Fix an access to VXSAT
* Expose RV32 cpu to RV64 QEMU
* Don't clear PLIC pending bits on IRQ lowering
* Make PLIC zeroth priority register read-only
* Set vtype.vill on CPU reset
* Check and update APLIC pending when write sourcecfg
* Avoid dropping charecters with HTIF
* Apply FIFO backpressure to guests using SiFive UART
* Support for control flow integrity extensions
* Support for the IOMMU with the virt machine
* set 'aia_mode' to default in error path
* clarify how 'riscv-aia' default works

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* tag 'pull-riscv-to-apply-20241031-1' of https://github.com/alistair23/qemu: (50 commits)
  target/riscv: Fix vcompress with rvv_ta_all_1s
  target/riscv/kvm: clarify how 'riscv-aia' default works
  target/riscv/kvm: set 'aia_mode' to default in error path
  docs/specs: add riscv-iommu
  qtest/riscv-iommu-test: add init queues test
  hw/riscv/riscv-iommu: add DBG support
  hw/riscv/riscv-iommu: add ATS support
  hw/riscv/riscv-iommu: add Address Translation Cache (IOATC)
  test/qtest: add riscv-iommu-pci tests
  hw/riscv/virt.c: support for RISC-V IOMMU PCIDevice hotplug
  hw/riscv: add riscv-iommu-pci reference device
  pci-ids.rst: add Red Hat pci-id for RISC-V IOMMU device
  hw/riscv: add RISC-V IOMMU base emulation
  hw/riscv: add riscv-iommu-bits.h
  exec/memtxattr: add process identifier to the transaction attributes
  target/riscv: Expose zicfiss extension as a cpu property
  disas/riscv: enable disassembly for compressed sspush/sspopchk
  disas/riscv: enable disassembly for zicfiss instructions
  target/riscv: compressed encodings for sspush and sspopchk
  target/riscv: implement zicfiss instructions
  ...

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

3 files changed, 93 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