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-rw-r--r--docs/system/riscv/virt.rst17
1 files changed, 17 insertions, 0 deletions
diff --git a/docs/system/riscv/virt.rst b/docs/system/riscv/virt.rst
index 8e9a2e4dda..60850970ce 100644
--- a/docs/system/riscv/virt.rst
+++ b/docs/system/riscv/virt.rst
@@ -94,6 +94,12 @@ command line:
 
   $ qemu-system-riscv64 -M virt -device riscv-iommu-pci (...)
 
+It also has support for the riscv-iommu-sys platform device:
+
+.. code-block:: bash
+
+  $ qemu-system-riscv64 -M virt,iommu-sys=on (...)
+
 Refer to :ref:`riscv-iommu` for more information on how the RISC-V IOMMU support
 works.
 
@@ -123,12 +129,23 @@ The following machine-specific options are supported:
   MSIs. When not specified, this option is assumed to be "none" which selects
   SiFive PLIC to handle wired interrupts.
 
+  This option also interacts with '-accel kvm'.  When using "aia=aplic-imsic"
+  with KVM, it is possible to set the use of the kernel irqchip in split mode
+  by using "-accel kvm,kernel-irqchip=split".  In this case the ``virt`` machine
+  will emulate the APLIC controller instead of using the APLIC controller from
+  the irqchip.  See :ref:`riscv-aia` for more details on all available AIA
+  modes.
+
 - aia-guests=nnn
 
   The number of per-HART VS-level AIA IMSIC pages to be emulated for a guest
   having AIA IMSIC (i.e. "aia=aplic-imsic" selected). When not specified,
   the default number of per-HART VS-level AIA IMSIC pages is 0.
 
+- iommu-sys=[on|off]
+
+  Enables the riscv-iommu-sys platform device. Defaults to 'off'.
+
 Running Linux kernel
 --------------------